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Change of magnetic properties in austenitic stainless steels due to plastic deformation

Authors:
Tatiana Oršulová at University of Žilina
Tatiana Oršulová
P. Palček at University of Žilina
P. Palček
Marek Tadeusz Roszak at Silesian University of Technology
Marek Tadeusz Roszak
Milan Uhríčik at University of Žilina
Milan Uhríčik
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Abstract and Figures

Austenitic stainless steels, investigated in this research, belong into a group of the so-called high-alloy TRIP (Transformation Induced Plasticity) steels. The nondestructive evaluation (NDE) methods were used for determination of plastic deformation influence in investigated materials. The NDE methods permit products to be inspected throughout their service life, to determine when to repair or replace a particular part. The main goal of this study was to measure and thus separate different levels of applied plastic deformation of selected conductive biomaterials. Two different devices were used to evaluate the effect of plastic deformation. The first device was commercially available magnetic field sensor GF708. The second device was Magnet Physik, on which is possible to determine magnetic quantities (remanence, coercivity), make measurements with surrounding coils to determine the magnetic mean values and measure at temperatures up to 200 °C. Both of those devices are suitable for measuring the magnetic properties. Effect of plastic deformation was observed by the light microscope, as well.
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ScienceDirect
Available online at www.sciencedirect.com
Available online at www.sciencedirect.com
ScienceDirect
Structural Integrity Procedia 00 (2016) 000–000
www.elsevier.com/locate/procedia
2452-3216 © 2016 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the Scientific Committee of PCF 2016.
XV Portuguese Conference on Fracture, PCF 2016, 10-12 February 2016, Paço de Arcos, Portugal
Thermo-mechanical modeling of a high pressure turbine blade of an
airplane gas turbine engine
P. Brandãoa, V. Infanteb, A.M. Deusc*
aDepartment of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisboa,
Portugal
bIDMEC, Department of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisboa,
Portugal
cCeFEMA, Department of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisboa,
Portugal
Abstract
During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions,
especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent
degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict
the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation
company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model
needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were
obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D
rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The
overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a
model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
© 2016 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the Scientific Committee of PCF 2016.
Keywords: High Pressure Turbine Blade; Creep; Finite Element Method; 3D Model; Simulation.
* Corresponding author. Tel.: +351 218419991.
E-mail address: amd@tecnico.ulisboa.pt
Procedia Structural Integrity 13 (2018) 1689–1694
2452-3216
2018 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the ECF22 organizers.
10.1016/j.prostr.2018.12.352
Available online at www.sciencedirect.com
ScienceDirect
Structural Integrity Procedia 00 (2018) 000–000
www.elsevier.com/locate/procedia
2452-3216 © 2018 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the ECF22 organizers.
ECF22 - Loading and Environmental effects on Structural Integrity
Change of magnetic properties in austenitic stainless steels due to
plastic deformation
Tatiana Oršulováa*, Peter Palčeka, Marek Roszakb, Milan Uhríčika, Milan Smetanaa,
Jozef Kúdelčíka
aFaculty of Mechanical Engineering & Faculty of Electrical Engineering, University of Žilina, 010 26 Žilina, Slovak republic
bInstitute of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego 18a St, 44-100 Gliwice, Poland
Abstract
Austenitic stainless steels, investigated in this research, belong into a group of the so-called high-alloy TRIP (Transformation
Induced Plasticity) steels. The nondestructive evaluation (NDE) methods were used for determination of plastic deformation
influence in investigated materials. The NDE methods permit products to be inspected throughout their service life, to determine
when to repair or replace a particular part. The main goal of this study was to measure and thus separate different levels of
applied plastic deformation of selected conductive biomaterials. Two different devices were used to evaluate the effect of plastic
deformation. The first device was commercially available magnetic field sensor GF708. The second device was Magnet Physik,
on which is possible to determine magnetic quantities (remanence, coercivity), make measurements with surrounding coils to
determine the magnetic mean values and measure at temperatures up to 200 °C. Both of those devices are suitable for measuring
the magnetic properties. Effect of plastic deformation was observed by the light microscope, as well.
© 2018 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the ECF22 organizers.
Keywords: nondestructive evaluation; magnetic properties; plastic deformation; austenitic stainless steels
1. Introduction
External forces cause material deformation or deformation with a sufficiently powerful force that breaks through
the fracture. Due to the influence of the external forces, the material creates a tension that is manifested by a certain
arrangement of the mechanical stress (Jankura et al., 2008).
* Corresponding author. Tel.: +421-41-513-2632.
E-mail address: tatiana.orsulova@fstroj.uniza.sk
10.1016/j.prostr.2018.12.352 2452-3216
© 2018 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the ECF22 organizers.
Available online at www.sciencedirect.com
ScienceDirect
Structural Integrity Procedia 00 (2018) 000–000
www.elsevier.com/locate/procedia
2452-3216 © 2018 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the ECF22 organizers.
ECF22 - Loading and Environmental effects on Structural Integrity
Change of magnetic properties in austenitic stainless steels due to
plastic deformation
Tatiana Oršulováa*, Peter Palčeka, Marek Roszakb, Milan Uhríčika, Milan Smetanaa,
Jozef Kúdelčíka
aFaculty of Mechanical Engineering & Faculty of Electrical Engineering, University of Žilina, 010 26 Žilina, Slovak republic
bInstitute of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego 18a St, 44-100 Gliwice, Poland
Abstract
Austenitic stainless steels, investigated in this research, belong into a group of the so-called high-alloy TRIP (Transformation
Induced Plasticity) steels. The nondestructive evaluation (NDE) methods were used for determination of plastic deformation
influence in investigated materials. The NDE methods permit products to be inspected throughout their service life, to determine
when to repair or replace a particular part. The main goal of this study was to measure and thus separate different levels of
applied plastic deformation of selected conductive biomaterials. Two different devices were used to evaluate the effect of plastic
deformation. The first device was commercially available magnetic field sensor GF708. The second device was Magnet Physik,
on which is possible to determine magnetic quantities (remanence, coercivity), make measurements with surrounding coils to
determine the magnetic mean values and measure at temperatures up to 200 °C. Both of those devices are suitable for measuring
the magnetic properties. Effect of plastic deformation was observed by the light microscope, as well.
© 2018 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the ECF22 organizers.
Keywords: nondestructive evaluation; magnetic properties; plastic deformation; austenitic stainless steels
1. Introduction
External forces cause material deformation or deformation with a sufficiently powerful force that breaks through
the fracture. Due to the influence of the external forces, the material creates a tension that is manifested by a certain
arrangement of the mechanical stress (Jankura et al., 2008).
* Corresponding author. Tel.: +421-41-513-2632.
E-mail address: tatiana.orsulova@fstroj.uniza.sk
1690 Tatiana Oršulová et al. / Procedia Structural Integrity 13 (2018) 1689–1694
There are many techniques that allow determination and evaluation of mechanical changes in materials. One of
them is the nondestructive evaluation (NDE). The rapidly expanding role of the NDE methods in manufacturing,
power, construction and biomedical industries has generated a large demand for practitioners, engineers, and
scientists with knowledge of the subject. The NDE presents current practices, common methods and equipment,
applications and the potential and limitations of current NDE methods, in addition to the fundamental physical
principles underlying the NDE. Those methods can have a dramatic effect on the cost and reliability of products. The
methods can be used to evaluate prototype designs during the product development, to provide feedback for process
control during manufacturing and to inspect the final product prior to service. Additionally, the NDE methods permit
products to be inspected throughout their serviceable life to determine when to repair or replace a particular part. In
today’s economy, the concepts ‘‘repair or retire for cause’’ and ‘‘risk-informed inspection’’ are becoming very
important (Shull, 2002). The NDE offers a margin of safety for this equipment and gives users the means with which
to determine when equipment must be repaired or retired. The basic principle of NDE is quite simple. To determine
the quality or integrity of an item nondestructively, one should simply find a physical phenomenon that will interact
with and be influenced by a test specimen without altering the specimen’s function. This article focuses on one
possible electromagnetic NDE application: evaluation of mechanical conditions of the austenitic steels through a
measurement of their magnetic properties. The main goal is to measure and thus separate different levels of applied
plastic deformation of concrete conductive biomaterials. Commercially available magnetic field sensor and device
Magnet Physik are used for this purpose and obtained results are presented and discussed.
2. Experimental material
The austenitic stainless steels are the ternary alloys of Fe-Cr-Ni. Their microstructures consist of very clean FCC
(Face Centered Cubic) crystals in which all the alloying elements are held in a solid solution. Those steels are called
austenitic because of their final structure. They are austenitic at the room temperature. The austenitic stainless steels
are widely applied in chemical, petrochemical, biomedical and many other fields. The most widely used austenitic
stainless steels are the following grades: AISI 304, 316L and 316Ti. Those materials belong among the types of the
so-called high-alloy TRIP (Transformation Induced Plasticity) steels. These types of steels contain substantial
number of alloying elements such as Cr and Ni, which improve pitting and corrosion resistance (Rodríguez-
Martínez et al., 2011). The most common of selected steels is the AISI 304 - this steel contains essentially 18% of
Cr and 8% of Ni. Content of C is limited to maximum of 0.08%. This material is paramagnetic and it has a cubic
closed γ-phase. After the plastic deformation, the phase is transformed to a BCC (Body-Centered Cubic) α'-
martensite phase. Thus, this material becomes partially ferromagnetic after the plastic deformation. Many reports
refer that the magnetic effects of martensite content in AISI 304 is caused by the progressive cold rolling (Tourki et
al., 2005; Tukur et al., 2014; Vertesy et al., 2005). The AISI 304 has the following selected properties: a high
ductility, excellent drawing, forming, and spinning. A low carbon content means less carbide precipitation in the
heat-affected zone during the welding and a lower susceptibility to intergranular corrosion. It also resists to most
oxidizing acids and salt spray. Those properties make the AISI 304 widely used stainless steel.
Both the AISI 316L and AISI 316Ti include higher percentage of alloying elements. Different chemical
composition is reason why these steels change their primary deformation mechanism from twining (in 304 grades)
to slipping: typical for 316 grades (Correa et al., 2017). Differences in the microstructure after the heat treatment
were observed by an optical microscope. In microstructure of the AISI 304 in initial state, there were visible
austenitic grains with different size. The annealing twins were also present and a relatively large amount of MnS
based inclusions. A representative sample of the evaluated microstructures, the AISI 304 steel, additionally contains
a significant proportion of α'-martensite (Fig.1a). Solution annealing (1050 ° C / 35 min) resulted in the structural
homogenization of the materials and the effect of the prior technological treatment was eliminated. Rapid cooling in
the water prevented phase and interstitial excretion inside the matrix and also along the grain boundaries. In the
examined microstructures there was a significant reduction of plastic deformation, with simultaneous dissolving the
bulk of sulphides, oxides and other compounds. The grains boundaries are affected by heat treatment. In the AISI
304 microstructure, significant annealing twins are visible (Fig.1b).
Tatiana Oršulová et al. / Procedia Structural Integrity 13 (2018) 1689–1694 1691
Author name / Structural Integrity Procedia 00 (2018) 000–000 3
a)
b)
Fig. 1 Microstructures of the AISI 304 a) initial state; b) after solution annealing
Fig. 2 Vickers hardness test of investigated materials
For verification of these structural changes in the tested material, a hardness test after Vickers was used (Fig. 2).
During the heat treatment the values of hardness decreased. After the recrystallization annealing of deformation
reinforced steel, a gradual decrease in hardness occurred. Decrease of hardness was related to a gradual change of α'-
martensite to austenite. The structure was gradually changed to the equilibrium by the heating process. In the
recrystallization annealing with a 15-minute time-out, there was a slight increase in the hardness value. This may be
caused by refining of the austenitic grain. For longer durations at T = 850°C, the hardness value again decreased. In this
case, it may have occurred that longer holding time caused an increase and thickening of the austenitic grain. At the
dissolution annealing temperature, the lowest hardness values were reached. A homogenization of structure has been
achieved by the rapid cooling in water, thus there were no carbides, oxides and other inclusions produced. These
structure elements would affect the resulting austenitic structure of the steel, if they were present. A similar case was
also found in work of Tukur et al., 2014, where the influence of temperature on mechanical properties, such as
hardness, strength and ductility, was evaluated. Sensitized sample of AISI 304 grade has the highest hardness value (41
HRC) compared to the sample at baseline (36 HRC) and after the annealing (20.4 HRC). Increased hardness was
attributed to carbide formation along the grain boundaries of the sensitized specimen. The excluded carbides impeded
the dislocation movement and reduced the deficiencies within the grit of the sensitized steel (Tukur et al., 2014).
3. Experimental procedure
Configuration for realization of the experiments is introduced in this section. The given experimental material is
the conductive stainless steel specimens that are nondestructively inspected. Three different austenitic steel grades
were evaluated: AISI 304, 316L and 316Ti grade. The specimens had initially the brick shape, with initial
1692 Tatiana Oršulová et al. / Procedia Structural Integrity 13 (2018) 1689–1694
dimensions: 20 mm x 10 mm x 10 mm. The all specimens were previously annealed at the defined temperature for
solution annealing (1050°C/35min.). This regime was defined as the initial state (IS).
Further, the controlled plastic deformation was applied. The deformation was performed by mechanical pressing
of the opposite sides of these samples. Exact values of the plastic deformations were inspected: T1 = 0%, T2 = 1%,
T3 = 2%, T4 = 5%, T5 = 10%, T6 = 20%, T7 = 30% and T8 = 40%. This value represents the percentage shortening
of the length of the specimen after the plastic deformation, in comparison with the reference sample.
The commercially available sensor of GF708AKA (Sensitec GmbH) was used in first measuring of the magnetic
field. This magnetic field sensor is based on the Giant-Magneto-Resistive (GMR) effect. Its functional magnetic
layer is pinned within a synthetic spin-valve connected as a Wheatstone bridge. With its on-chip flux concentrators
an extremely large sensitivity can be achieved, resulting in an almost step-like bipolar transfer curve. This way the
sensor is predestined for the key application field: as a highly sensitive magnetic field sensor. Due to the spin valve
technology the transfer curve within ±1 mT features an extremely high sensitivity of 130 mV/V/mT with very low
coercitivity at the same time. The GMR sensor was positioned in each axis of the 3D coordinate system with respect
to the investigated material, respectively. It means that its sensitive axis was oriented in that way to be able to sense
all the individual components of the residual magnetic field. Thus, the magnetic field values were picked-up, to be
the resulting graphs displayed. Measured magnetic field component in a given direction was represented as an
output voltage signal of the sensor. This value was picked up from the diagonal of the Wheatstone’s bridge (Mach,
2012; Smetana, 2016; Stubendekova, 2015).
The lift-off parameter was set to LO = 1mm. This value was kept at a constant level for all the specimens. A
classical 2D raster scan was performed for all the surfaces of each specimen. Only the maximum value of the
residual magnetic field was taken into account to be the graphical dependences visualized. The rectangular area
shape of the 2D scan was defined as follows: number of scanning lines N = 120, step distance of S = 0.1 mm,
scanned length per line of SP = 40 mm. The measured data were acquired using the data acquisition card (DAQ)
with resolution of res = 16bits/channel, sampling frequency of fs = 10kS/sec. The user interface for data
manipulation, controlling the stage and processing the data was designed using the LabVIEW software (virtual
instrumentation).
The second part of experimental measurements was realized on device Magnet Physik, which is used for measuring
of hysteresis loops. On this device, it is possible to determine magnetic quantities (remanence, coercivity), make
measurements with surrounding coils to determine the magnetic mean values and measure at temperatures up to 200
°C. The measurement was performed under normal conditions at room temperature. The temperature of specimens was
21 °C. The magnetic excitation fields that are necessary to record a hysteresis loop were generated by the
electromagnet EP 3. The maximum current of the electromagnets power supply was set to ±10 A and time of
increasing of current to maximum to 40 s. During all the measurements the demagnetization was on.
4. Results
Results of the experimental measurements are presented in this section. After each 2D raster scan of the whole
biomaterial shell, the maximum of the gained values was extracted. This procedure was performed three times
(individually for X, Y, Z axis). These values were used for construction of the following graphs. Further, the module
value was computed as SQRT of summed squares of the three spatial values. As can be seen from the results, with
increasing plastic deformation level, the output signal of the GMR sensor increased, as well. This means that the
higher the deformation, the higher the magnetic response of the specimen. Of course, the great differences between
individual materials were revealed: the strongest signals were gained for the AISI 304 biomaterial. This is in
correlation with theoretical background (the highest amount of the ferromagnetic martensitic components was
present here). Further, the responses valid for the AISI 316L and AISI 316Ti showed that the residual magnetic field
was rapidly decreasing than for the previous one. Although, the AISI 316L material has better resolution among the
individual field components, in comparison to the AISI 316Ti. Practically, it has to be concluded that deformation
levels lower than 5% were not successfully detected by the sensor. On the other hand, change in magnetic
biomaterial properties (caused by the mechanical deformation) was clearly revealed. The scanning procedure
performed in all the three axis of the 3D coordinate system, showed that it is sufficient to sense only one component.
Resulting value is approximately the same for each component. Fig. 3 displays the module value of the inspected
Tatiana Oršulová et al. / Procedia Structural Integrity 13 (2018) 1689–1694 1693
Author name / Structural Integrity Procedia 00 (2018) 000–000 5
materials in one graph. This comparison showed non-linear dependences between applied plastic deformation and
the intrinsic magnetic field response. In fact, this is also in correlation with theory, which describes this phenomenon
from the material engineering point of view. Based on the results, it can be concluded that the most suitable material
for nondestructive evaluation purposes is AISI 304. Generally, all of the inspected materials can be evaluated, but
with respect to the sensitivity of the sensor and the deformation level.
a) b)
Fig. 4 Results from device Magnet Physik: a) comparison of magnetic properties of investigated steels in initial state; b) magnetic properties of
the AISI 304 after different degrees of deformation
Measurements realized on device Magnet Physic have demonstrated that from three chosen materials, only one
has got significant magnetic behavior - the AISI 304. It is caused by the presence of plastic deformation after
previous forming in evaluated material. This measurement failure was also caused by the low sensitivity of the
measuring device; it is possible to measure only specimens with stronger magnetism. On the other hand, this device
was able to record the results from slightly magnetic steel AISI 304. Fig. 4b) shows significant increase of
magnetism after the plastic deformation.
5. Conclusion
This article presented a study of electromagnetic nondestructive evaluation of austenitic stainless steels after
previous plastic deformation. Three different steel grades were evaluated with presence of the seven specific levels
of the plastic deformation. The commercially available 1D GMR sensor was used in the first step of research. Each
of the 3D coordinate systems components was sensed, so the sensor was rotated three times for the scanning
Fig. 3 Experimental results: residual magnetic field - maximum module gained values
1694 Tatiana Oršulová et al. / Procedia Structural Integrity 13 (2018) 1689–1694
procedure of each sample. The results showed that significant dependence between applied plastic deformation and
magnetic field response could be detected by the sensor. The main aim of this study was to show a detection ability
of used the sensor to bring appropriate results about various level of mechanical deformation of the samples. The
results showed that this information could be presented, although the plastic deformation levels lower than 5% could
not be successfully detected. Further, the 3D scanning procedure brought new information about the magnetic
behavior of the inspected specimens. This approach is quite new and may be helpful in better characterization and
understanding of the austenitic stainless steels. As could be seen, the mechanical and electromagnetic properties of
the same material vary together and it is a question of the appropriate sensing element to reveal their certain mutual
dependences nondestructively. The second step of research was a confirmation of presence of plastic deformation in
selected materials via device Magnet Physik. Mentioned measurement device was able to record only results for one
material - the AISI 304. Despite the measurement failure of the AISI 316 grades it can be said, that the research goal
was accomplished. A presence of different grades of plastic deformation in AISI 304 was confirmed.
The future steps of the authors will lead to quantitative characterization of the partially ferromagnetic martensite
components within the deformed austenitic stainless steel that may results in the so-called magnetic memory.
Acknowledgements
The research was supported by Scientific Grant Agency of Ministry of Education of Slovak republic VEGA
1/0683/15 and Visegrad Scholarship Programme.
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... During plastic deformation, most austenitic SS undergo a martensitic transformation from FCC-austenite phase to BCC-α ′ -martensite through HCP-ε -martensite as an intermediate structure [507]. Therefore, the magnetic properties of SS are strongly dependent on the plastic deformation-induced martensite transformation [797,805,806]. ...
... The magnetic properties of multiphase SS strongly depend on the fraction of magnetic (ferromagnetic) phases [803,[806][807][808]. Saturation magnetization changes monotonically with the amount of magnetic phase in SS [803,804]. ...
... The magnetic properties of multiphase SS strongly depend on the fraction of magnetic (ferromagnetic) phases [803,[806][807][808]. Saturation magnetization changes monotonically with the amount of magnetic phase in SS [803,804]. Consequently, magnetic characterization has been used to estimate the volume fraction of the α ′ -martensite phase in SS [802,805,806,809]. The amount of ferromagnetic phase can be determined as a function of the saturation magnetization (M s ). ...
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Due to the classification of Co as a CMR (carcinogenic, mutagenic, toxic to reproduction) as well as the classification of both Co and WC as CRM (critical raw materials) more and more research is being carried out to investigate possible substitutes for WC-Co hardmetals. To directly compare their microstructure as well as mechanical and thermophysical properties, five very different hardmetals were investigated. For this purpose, the compositions WC-Co, WC-FeNiMn, WC-HEA, NbC-Co and HEC-Co were selected in order to investigate alternative binders for cobalt as well as different alternative hard phases for WC. The results of the hardness measurements showed that for the hardmetals with alternative binders (WC-FeNiMn and WC-HEA) hardness values of 1327 HV10 and 1299 HV10 comparable to WC-Co with 1323 HV10 can be achieved. When WC is replaced by HEC as the hard phase, a significantly higher hardness of 1543 HV10 can be obtained, demonstrating the great potential of high-entropy carbides. Furthermore, the hot hardness measurements between RT and 900 °C showed significantly higher values (up to approx. 290 HV10) for the WC-HEA and HEC-Co hardmetals compared to those of WC-Co. However, the fracture toughness of the alternative hardmetals was lower compared to that of conventional WC-Co hardmetals. In terms of thermophysical properties, the results of the hardmetals with alternative binders were close to those of WC-Co. Thus, it can be shown that it is possible to produce alternative hardmetals with comparable properties to WC-Co and that with further optimization they show great potential to replace WC-Co in the near future.
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... Most studies analyzing the correlation between the ferromagnetic content of a sample and electromagnetic measurement results are evaluating bulk samples, e.g. [11,19,[21][22][23][24][25][26]. These data are not directly applicable to thin subsurface layers, and thus a comparison of different methods for the determination of the created subsurface martensite content by cryogenic external turning is presented here. ...
Non-destructive, Contactless and Real-Time Capable Determination of the α'-Martensite Content in Modified Subsurfaces of AISI 304
Article
Full-text available
  • Oct 2022
  • J NONDESTRUCT EVAL
Cryogenic turning can be used to produce deformation-induced martensite in metastable austenitic steels. Martensite exhibits a higher hardness than austenite and increases the wear resistance of the workpiece. In order to reliably induce a desired martensite content in the subsurface zone during the turning process, a non-destructive, contactless and real-time testing method is necessary. Eddy current testing is an electromagnetic method that is non-destructive, non-contact and real-time capable. Furthermore, eddy current testing has been integrated into production processes many times. Eddy current testing can be used to detect the transformation of paramagnetic austenite to ferromagnetic α-martensite based on the change in magnetic and electrical properties. Thus, the newly formed subsurface can be characterized and the manufacturing process can be monitored. The objective of this study was to understand the correlation of eddy current testing signals with newly formed α-martensite in the subsurface of AISI 304 and to quantify the amount formed. The measurements were performed within a machining center. Several methods for reference measurement of martensite content are known in the literature. However, depending on the method used, large discrepancies may occur between the determined contents. Therefore, different analytical methods were used for reference measurements to determine the total martensite content in the subsurface. Metallographic sections, magnetic etching, Mössbauer spectroscopy, and X-ray diffraction with two different analytical methods were employed. Based on the correlation between the eddy current testing signals and the α-martensite content in the subsurface, process control of the manufacturing process can be achieved in the future.
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... It should also be noted that any changes in physical, including magnetic, parameters are determined by changes occurring in the structure of the material (grain, dislocation, etc.), as well as a change in the level of residual stress in the material [17,18] under external deformation action. So, for example, the chemical composition of steel has a significant effect on the magnetic parameters, since varying the content of alloying elements in steel could lead to a change in the grain (for example, the formation of a reinforced structure, which, in turn, leads to an increase in the values of the coercive force [19,20]), dislocation (dislocations and their clusters impede the movement of domain walls and, hence, the process of magnetization [21]) of the structure, as well as to the transition of steel from one class to another (from purely austenitic to austenitic-ferritic, for example [22]). The analyses of magnetic parameters' behavior and their symmetry (or asymmetry) distributions could contribute to that of the stress-strain state parameters of the investigated material. ...
Influence of Elastic–Plastic Deformation on the Structure and Magnetic Characteristics of 13Cr-V Alloyed Steel Pipe
Article
Full-text available
  • Jun 2022
The principle of symmetry is one of the general methodological principles of science. The effects of any external influences, such as deformation, stresses, temperature, etc., could lead to the anisotropy (asymmetry) of properties in constructional materials. During operation, metal structures and machine parts are exposed to time-varying external mechanical loads, which can cause changes in the metal structure, the initiation of cracks, and, as a result, the destruction of the product. The application of nondestructive testing methods prevents changes in the stress–strain state and, consequently, the destruction of the object. This article contains the results of studying the effects of elastic–plastic deformation by uniaxial tension and torsion on the change in the structure and magnetic parameters of low-alloy 13Cr-V pipe steel. Modern methods of metallography and magnetic nondestructive testing methods were used as part of this study. The results of the EBSD analysis showed that deformation during torsion, in contrast to uniaxial tension, is unevenly distributed over the sample cross section. In the cross section of the sample, the most severely deformed grains with a change in their geometry are observed near the surface; in the center, there is no change in geometry. During tension, the deformation over the cross section of the sample is uniformly distributed. Correlations between the applied normal and tangential stresses and magnetic characteristics of the 13Cr-V structural steel were determined. Informative parameters that could be used for the development of nondestructive testing methodologies for solving concrete tasks were determined. Different methods of deformation lead to diverse structural changes in grain structure.
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... Several studies have already monitored the martensite formation upon plastic deformation of stainless steels with magnetic testing methods [4][5][6]. However, most nondestructive, magnetic testing methods lead to a misjudgment of the martensite fraction due to the inhomogeneous martensite distribution over the thickness [7]. ...
Generation of tailored subsurface zones in steels containing metastable austenite by adaptive machining and validation by eddy current testing
Article
  • Oct 2020
In order to withstand high mechanical and tribological loads, it is important that the components not only have a high core ductility but also a hard surface. Typically, a suitable microstructure is created by heat treatment processes before the workpiece is machined. However, these processes are time and energy consuming and can lead to component distortion. It would therefore be of great advantage if no additional heat treatment process would be required to produce a hardened subsurface zone. Since turning is often already integrated as a machining process in production lines, it would be advantageous to create a hardened subsurface within this process. As there is no possibility to measure the hardness directly during the turning process, a soft sensor was developed to determine the properties of the subsurface directly during the machining process. Steels with metastable austenite are of particular interest in this context, as metastable austenite can be converted into martensite by deformation. The amount of martensite produced in the subsurface can be adjusted provided that suitable turning parameters can be found. For this purpose, a process parallel material removal simulation was used to determine the actual conditions governing the process. It was found that there is a correlation between the martensite content and the amplitude of the 3rd harmonic of eddy current testing. Therefore, an eddy current sensor accompanying the process can be used as a basis for controlling the turning process for tailored martensite volume content adjustment.
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... However, under the action of aggressive halide ions, local breakdown of passivity occurs, causing pitting corrosion [2,[5][6]. The susceptibility of the austenitic stainless steels to the intergranular corrosion is connected with their exposition in the temperature range of 500 -800 °C ("critical temperatures") and with consequent slow cooling in the air which leads to the precipitation of M23C6 chromium-rich carbides on the grain boundaries [7][8][9]. The precipitation of chromium carbides consumed the main alloying element -chromium from a narrow band along the grain boundary and this makes the zone anodic to the unaffected grains. ...
Susceptibility to the intergranular attack in austenitic stainless steels
Article
Full-text available
  • Jan 2020
Intergranular corrosion is very dangerous local corrosion form that often leads to the dislodgment of individual grains and to the intensive negative influence on the mechanical properties of the material. The susceptibility of the austenitic stainless steels to the intergranular corrosion is connected with their exposition in the temperature range of 500-800 °C (“critical temperatures”) and with consequent slow cooling in the air which leads to the precipitation of chromium-rich carbides at the grain boundaries. This process consumes chromium from a narrow band along the grain boundaries and the steel becomes to be sensitized and susceptible to the intergranular corrosion in aggressive environments. This article deals with the susceptibility to the intergranular corrosion of three austenitic stainless steels (AISI 304, 316L, 316Ti). Both “as received” and improperly heat treated specimens (sensitization for 10 hours at 650 °C, cooling in the air) were tested by ASTM A262 standard method, A and E practices. Optical microscopy and SEM analysis were used for the assessment of the obtained results.
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... The passive surface film makes the stainless steel resistant to the uniform corrosion in oxidation environments (Jambor et al., 2018;Lipinsky, 2019;Oravcová et al., 2018;Oršulová et al., 2018;Szklarska-Smialowska, 2005). However, a presence of halides can evoke local breakdown of the protective film and, consequently, dangerous and destructive pitting corrosion (Szklarska-Smialowska, 2005;Liptáková, 2009;Zatkalíková et al., 2019). ...
Influence of temperature on corrosion resistance of austenitic stainless steel in cl− containing solutions
Article
Full-text available
  • Dec 2019
Temperature is considered a complicated external factor of the susceptibility of stainless steels to the pitting. This paper deals with the corrosion behaviour of AISI 316Ti stainless steel in temperature range 22 - 80°C in aggressive chloride environments (3 and 5% FeCl 3 solutions). The corrosion resistance of tested steel is evaluated on the base of results of exposure immersion tests and cyclic potentiodynamic tests. According to the obtained results the resistance of AISI 316Ti to the pitting is markedly affected by temperature changes in the range 22 – 80°C. Intensity of corrosion attack increases with the rise of Cl ⁻ concentration. Gentle changes of temperature and Cl ⁻ concentration cause significant differences in character of local damage. The appearance of pitted surfaces changes with the rise of the temperature (a density of pitting increases, a size of pits decreases). The strongest change in appearance is observed between 40 and 50ºC.
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... According to various studies, e.g. (Kurc et al., 2010;Oršulová et al., 2018;Ramirez et al., 2013), the corrosion resistance of stainless steels is also negatively influenced by the previous plastic deformation. The presented paper deals with the pitting corrosion resistance of AISI 304 austenitic stainless steel with unmodified surface ("as received" surface) in low pH (1.2) 1M chloride solution at the temperatures of 20 and 50 °C. ...
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Scientific Journals of the Maritime University of Szczecin 71 (143) 2022 Zeszyty Naukowe Akademii Morskiej w Szczecinie 71(143) 2022
Book
Full-text available
  • Sep 2022
Dear Readers, We are pleased to present you the next issue of our journal, Scientific Journals of the Maritime University of Szczecin. Fourteen articles are presented in this issue, the problems of which fall under the following subject areas: Civil Engineering and Transport, Material and Mechanical Engineering, Environmental Engineering, Mining and Energy, Information and Communication Technology, Economics, Management and Quality Science, Sustainability Management. We are pleased that the manuscripts submitted to us cover a wide field of research, thus giving our readers the opportunity to analyze and give their opinion on a variety of research problems. In the Civil Engineering and Transport section, we present two studies. The first study investigated the effects of buoys and solid mass on mooring lines and the dynamic response of the floating platform. The results of the analysis show that increasing the number of buoys at constant volume contributes to a decrease in the amplitude of wave and tilt motion, while lifting motion increases slightly. On the other hand, adding a buoy and clump weight to the mooring line reduces the tension of the vibration amplitude. The second study characterizes the distribution chain of liquefied natural gas in Poland, paying particular attention to the possibilities of road transport. It has been noted that during transportation and storage, LNG vaporization, known as boil-off gas, is a significant problem leading to an increase in tank pressure. Hence, one solution to this problem is to compress it to high pressure, which produces compressed gaseous fuels. In the Material and Mechanical Engineering Section, we have six manuscripts. As the authors write in the first study, one of the primary hazards associated with the operation of marine and deep-sea vessels-particularly ship power plants-are fires and explosions, which cause accidents and incidents with an average frequency of up to every 60 days. The article discusses the explosion hazard status of the crankcase of main propulsion engines of various types of vessels. The evaluation was based on the results of statistical analysis of historical data from 1972–2018. Based on the analysis, it was generally shown that the risk of a crankcase explosion affects ships of all ages and that the number of serious incidents remains constant over the period studied. It is interesting to note that half of all incidents occurred on vessels younger than 15 years. The second article describes the prospects for ultrasonic cleaning of shell-and-tube heat exchangers used, among others, on ships. This is because the main problem of seawater heat exchangers is their clogging – as a result of the operation, over time a process of overgrowth begins (e.g., algae), leading to reduced efficiency. In order to obtain information about the distribution of ultrasonic power inside the reactor, the authors conducted a finite element simulation using a designed test reactor represented by a shell-and-tube heat exchanger with ultrasonic-assisted cleaning. The simulation results are presented in the article. The authors of the next article in this section point out that concrete is currently the most widely used man-made composite material and is second only to water across the range of materials used. This paper presents the results of a study of the effect of partial replacement of Portland cement with fly ash on the strength parameters, frost resistance and carbonation of concrete in comparison with a reference concrete and concrete containing a conventional additive – silica fly ash. The results obtained confirmed the feasibility of producing plain concrete modified with fly ash from thermal treatment of sewage sludge, while demonstrating the compliance of concrete parameters with environmental requirements for the leaching of heavy metals. Concrete was also analyzed in the following article. It presents the effects of the addition of steel and propylene fibres on the mechanical properties of floor concretes, such as compressive and tensile strengths in the flexural test. It was shown that the amount of steel fibres dosed in the study, regardless of their shape, does not adversely affect the consistency and workability of the concrete mixture. On the other hand, the addition of polypropylene fibres has a significant impact on the properties of the concrete mix. In the introduction of the following article, the authors explain that a digital twin is a digital replica, a mathematical model of a given object, product, process, system or service. It enables the acquisition of a significant amount of data and can be used to obtain comprehensive knowledge about a given object, its behaviour and reactions. The authors analyzed the operation of a rotating bearing in a wind turbine structure using a digital twin model, and more specifically, analyzed the distribution of loads prevailing in the rotor blade bearings at wind turbine limit loads. The basic types of the most commonly used rim bearings for wind turbine applications are analyzed. In doing so, a methodology for building computational models of rim bearings using the finite element method was developed, as well as an original method of simulating rolling elements with rod elements (for rollers and super elements) for load-bearing balls was proposed. The subject of research in the last article of this section is stainless steels widely used in various automotive parts. Knowing that some of them are exposed to the external environment, the pitting corrosion resistance of two austenitic stainless steels was analyzed, i.e., AISI 304 and AISI 316L in road salt solutions of 5% wt. and 10% wt. Experimental results confirmed the lower pitting corrosion resistance of AISI 304 stainless steel in a 10% wt. road salt solution. We present one article in the Environmental Engineering, Mining and Energy section. It notes that the biggest problem of creating a numerical model of a coal seam is the insertion of discontinuity lines: faults, seam connection lines, wedging, etc. Therefore, proprietary methods were developed to determine the spatial location of faults, implemented in Geolisp in CAD. A method is presented for calculating the spatial position of a fault based on existing contours reaching it from both sides, a method based on the assumption that the slope of the deck upstream and downstream of the fault is constant, a method based on making independent surfaces of the updip and downdip sides with kriging extrapolation, a method based on transferring the fault from the deck above it or the Carboniferous roof. It was assumed that the correct introduction of the fault course is important for the accuracy of forecasting the impact of mining operations on the rock mass and surface. Two studies make up the Information and Communication Technology section. The Automatic Identification System (AIS) device is mandatory on ships that comply with the International Convention for the Safety of Life at Sea (SOLAS), the first study reads. AIS is designed to monitor vessel traffic in order to improve shipping safety. In their study, the authors compare the execution speed of geospatial queries in the relational database engine PostgreSQL and the non-relational database engine MongoDB. Four AIS datasets, four test polygons with different numbers of vertices, and a reference point on the fairway were defined for the study. The tests were used to evaluate the execution of queries in the database, which shows the number of ships in a given area and the number of ships within a given distance from a defined point. Test results say that test queries are executed faster, and data stored in the database takes up less disk space in MongoDB compared to PostgreSQL. Justifying the need for the research, the authors say that faster geospatial analysis of AIS messages can improve navigation safety by detecting dangerous situations earlier. The second article in this section highlights the use of satellite tracking during an environmental disaster at sea and evaluates the feasibility of using remote sensing images captured by satellites using multispectral cameras and Synthetic Aperture Radar (SAR). The purpose of the analysis is to evaluate selected remote sensing methods for detecting and tracking marine debris. The research value of the analysis is determined by the fact that the study was conducted in real-time at the time of the incident. The Economics, Management and Quality Science section is filled with one article. The object of research inquiry in this case was the pallet. The purpose of the article was to present the issues of pallet pool players’ strategies and the organizational, operational and market challenges they face in such a way that they are better understood by all supply chain players. The author proposes adopting a value-added synergy perspective as an alternative, understood as different and complementary, rather than excluding opportunities for other approaches to supply chain value. The final section, Sustainability Management, begins with a study highlighting the impact of increasing container throughput in the northern Adriatic ports on air quality. A comparative analysis of air quality consisting of certain environmental parameters taken from selected measuring stations near the container terminals of the northern Adriatic ports of Rijeka, Trieste, Koper and Venice was carried out. The study showed that the increase in container throughput in the ports of the northern Adriatic did not affect the deterioration of air quality in the urban areas of the various port cities. Air quality values in the ports of the northern Adriatic are well below the limits set by the EU Directive in the area of air quality (2008/50), i.e., they do not negatively affect the health of the residents of the analyzed cities. The subject of the next article was the relationship between the seaport and the city in the aspect of sustainable development, particularly in environmental terms. The consideration was based on the thesis that the introduction of the concept of sustainable development in the port can stimulate the creation of green cities. A case study of the sustainable development of the Twin Port of Bremen was used in the deliberations. Port development has been shown to stimulate GDP growth, increase employment, develop urban infrastructure and contribute to the enrichment of port cities. And the development of ports on an environmental basis also becomes a stimulus for green city development. I hope that the presented studies will meet with wide interest, and at the same time inspire various interdisciplinary thoughts, discussions and research. dr hab. Izabela Dembińska, Associate Professor Editor-In-Chief Szczecin, 30.09.2022
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Eddy Current Detection of the Martensitic Transformation in AISI304 Induced upon Cryogenic Cutting
Article
Full-text available
  • Oct 2020
  • STEEL RES INT
The combination of a hard subsurface layer and a ductile component core is advantageous for many applications. Steels are often heat treated to create such a hardened subsurface, which is both time- and energy-consuming. It is of great advantage to create a hardened subsurface directly within the machining process, as the production line of most components includes such a process to produce the desired geometric dimensions and surface quality. To achieve a martensitic subsurface layer within the machining process, cryogenic, external turning using a metastable AISI304 austenitic steel is used herein. Herein eddy current testing and the analysis of higher harmonics are used for the detection of the ferromagnetic, martensitic phase in the parent austenite. A good correlation is found between the martensite content and the amplitude of the signals measured. Therefore, eddy current testing is considered as a suitable real-time, nondestructive testing method, which forms the basis for the generation of a tailored, deformation-induced martensitic subsurface layer during external turning.
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Effect of Heat Treatment Temperature on Mechanical Properties of the AISI 304 Stainless Steel
Article
Full-text available
  • Feb 2014
Austenitic Stainless steels are sensitized when exposed to elevated temperature range of 470-750°C causes carbide precipitations at grain boundaries. Carbide precipitation can have deleterious effects on the resistance to intergranular corrosion and reduces the tensile properties of stainless steels, specifically strength and toughness. This paper evaluates an optimum heat treatment strategy for solution annealing of AISI 304 stainless steel after sensitization. Standard tensile and Hardness test specimens were fabricated using precision Lathe Machine. These samples were subjected to various heat treatment sequences, consisting of Sensitization at 660°C, followed by air cooling and solution annealed at five different temperatures: 1010°C, 1050°C, 1090°C, 1140°C and 1190°C, followed by water quenching. Heat treated samples were then mechanically tested for Hardness and Tensile properties. The influence of heat treatment process and temperature on mechanical properties of as-received, sensitized and solution annealed 304 stainless steels were evaluated. The investigation reveals that the sensitized samples give the highest hardness value at 666°C while highest hardness value was obtained on temperature of 1090°C for solution annealed 304 stainless steels. This temperature is found to be the optimum to avoid grain growth on solution annealed 304 stainless steels.
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Strain hardening behavior and microstructural evolution during plastic deformation of dual phase, non-grain oriented electrical and AISI 304 steels
Article
  • Jan 2017
  • MAT SCI ENG A-STRUCT
Strain hardening behavior and microstructural evolution of non-grain oriented electrical, dual phase, and AISI 304 steels, subjected to uniaxial tensile tests, were investigated in this study. Tensile tests were performed at room temperature and the strain hardening behavior of the steels was characterized by three different parameters: modified Crussard–Jaoul stages, strain hardening rate and instantaneous strain hardening exponent. Optical microscopic analysis, X-ray diffraction measurements, phase quantification by Rietveld refinement and hardness tests were also carried out in order to correlate the microstructural and mechanical responses to plastic deformation. Distinct strain hardening stages were observed in the steels in terms of the instantaneous strain hardening exponent and the strain hardening rate. The dual phase and non-grain oriented steels exhibited a two-stage strain hardening behavior while the AISI 304 steel displayed multiple stages, resulting in a more complex strain hardening behavior. The dual phase steels showed a high work hardening capacity in stage 1, which was gradually reduced in stage 2. On the other hand, the AISI 304 steel showed high strain hardening capacity, which continued to increase up to the tensile strength. This is a consequence of its additional strain hardening mechanism, based on a strain-induced martensitic transformation, as shown by the X-ray diffraction and optical microscopic analyses.
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Non-destructive testing of artificial hip and knee joints based on eddy current method
Article
  • Jan 2015
Non-destructive testing of conductive biomaterials by eddy current method is presented. The artificial joints are investigated in this study. The eddy current method is suitable for final inspection of prostheses before inserting an implant into human body. The main reason is to avoid repeated operations. An eddy current probe of absolute type is used for detection of defects with different depths using three frequencies. The numerical simulations are compared with experimental data in this article to select suitable frequency. The purpose is to determine which of the three frequencies provides the highest discrimination between magnitudes of eddy current signals gained for surface breaking cracks with different depths.
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Identification of Biomaterial Fatigue Cracks by ECT Method
Article
  • Jan 2016
The article deals with the eddy current technique for biomaterial fatigue cracks evaluation. The austenitic steel specimens with the presence of fatigue cracks are inspected under the same conditions. The mechanically induced fatigue cracks are made under the defined conditions, while a micro-plastic deformation is visible. Modular eddy current probe is used for the near-side inspection, while the harmonic signal is used for the driving. The gained results are presented and discussed in the paper.
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Induction heating of cylindrical nonmagnetic ingots by rotation in static magnetic field generated by permanent magnets
Article
  • Dec 2012
  • J COMPUT APPL MATH
Induction heating of cylindrical nonmagnetic billets by their rotation in static magnetic field is modeled. The magnetic field is produced by a system of appropriately arranged permanent magnets. The numerical model is solved by our own full adaptive higher-order finite element method in a monolithic formulation, i.e., both magnetic and temperature fields are solved simultaneously, respecting their mutual interaction. All principal nonlinearities are included in the model (permeability of ferromagnetic parts of the system as well as temperature dependences of physical parameters of the heated metal). The methodology is illustrated by two examples whose results are discussed.
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The kinetic of induced martensitic formation and its effect on forming limit curves in the AISI 304 stainless steel
Article
  • Aug 2005
  • J MATER PROCESS TECH
The kinetic and microstructure characteristics of plastic induced martensite of 304 stainless steel were studied. X-ray dispersing energy diffraction coupled to metallographic analyses (SEM) was made on this material. In the experimental process, the specimens were deformed at room and lower temperatures. The role of induced martensite phase on hardening behavior was first discussed by kinetic laws. An analysis, which considers the type of loading, is then conducted in order to give more indications on this new phase transformation.The influence of this plastic induced martensite on the drawability of the 304 stainless steel when compared to 316 which is much more stable, were also been appreciated through forming limit curves (FLC). This appreciation was achieved experimentally using Nakazima test expansion and theoretically through an analytical modeling by Marciniak–Kuczynski method. Finally, validations of the identified hardening laws were made by metallographic observations.
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Nondestructive Indication of Plastic Deformation of Cold-rolled Stainless Steel by Magnetic Minor Hysteresis Loops Measurement
Article
  • Jan 2005
  • J MAGN MAGN MATER
Cold-rolled austenitics stainless steel samples were non-destructively characterized by means of sets of magnetic minor hysteresis loops. The flat samples were magnetized by an attached yoke, and reliable parameters were obtained from the series of minor loops, without magnetic saturation of the samples. It was found, that some magnetic quantities, well known to be closely connected to the samples’ structure variation, especially relative coercivity and remanent induction, could be distinguished even more sensitively from minor loops, than from the major one.
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Experimental study on the martensitic transformation in AISI 304 steel sheets subjected to tension under wide ranges of strain rate at room temperature
Article
  • Jul 2011
  • MAT SCI ENG A-STRUCT
In this work, the martensitic transformation occurring in AISI 304 steel sheets subjected to tension at room temperature has been experimentally studied. Tensile tests performed on AISI 304 specimens are split into two different types; in situ tensile tests and macroscopic tensile tests. The former are conducted mounting the sample in a tensile micromachine originally developed in ENSAM/Metz within the range of strain rates 10−5 s−1≤ε˙≤10−3 s−1. The latter are performed under static and dynamic conditions of deformation within the range of strain rates 10−3 s−1≤ε˙≤102 s−1. Using X-rays diffraction technique, in situ tensile tests have allowed measuring the stress of the phases during loading by placing the tensile micromachine under the range of a PROTO goniometer. Additionally, the martensitic transformation has been recorded via mounting the tensile micromachine into a scanning electron microscope. The volume fraction of martensite has been measured in the post mortem specimens, Vα′≈70%. Moreover, the static macroscopic tensile tests, 10−3 s−1≤ε˙≤10−1 s−1, have been recorded using a high speed infrared camera. It has been proven that martensitic transformation takes place in AISI 304 steel for a temperature increase over ΔT>140K. The macroscopic dynamic tensile tests are performed within the range of strain rates, 1 s−1≤ε˙≤100 s−1. A considerable amount of martensite has been detected in the post mortem samples, Vα′≈35%. This proves that plastic deformation is the dominant mechanism responsible for the transformation phenomenon in this steel. The free energy supplied by straining the sample relegates to a secondary role the rise in temperature taking place during the course of plastic deformation.
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Effect of applied stresses on magnetostriction of low carbon steel
Article
  • Oct 1996
  • NDT&E INT
We have measured the magnetostriction of low carbon steel specimens while applying magnetic fields, being both parallel and perpendicular to the uniaxial applied stress. An individual domain of a polycrystalline steel is elongated in its magnetization direction, which coincides with one of the crystallographic axes, 〈100〉. The magnetization appears as a result of the domain wall movement induced by the applied magnetic field. The rotation of the domain magnetization participates, when the field becomes larger. As the magnetic field is increased, the magnetostriction in the magnetization direction first increases and then shows a maximum when the rotation of the domain magnetization starts to occur. Since the stress affects the domain structure through magnetoelastic interaction, the maximum magnetostriction shows the stress dependence. The magnetoelastic interaction tends to increase the volume of the domains being either parallel to the tensile stress or perpendicular to the compressive stress. The amount of the domain wall movement, equivalently the maximum magnetostriction, is thus larger for the magnetization which is either perpendicular to the tensile stress or parallel to the compressive stress. In the experiment, the maxima of magnetostriction, up to 17 × 10−6, were measured with sufficient accuracy using semiconductor strain gauges attached to the specimens. The results support the above physical prediction. We found that the stress dependence of the maxima is almost insensitive to the relation between the rolling direction and the loading direction, which ensures that the magnetostriction method is suitable for the residual stress measurement.
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