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High-strength aluminum is used extensively in industry, with welding being a widely used fabrication method. This work focuses on welding of 6061-T651 aluminum and establishment of the hardness–tensile properties relationship in the heat-affected zone (HAZ) of a gas metal arc weld using 4043 filler material. Test welds were prepared from 12.7-mm-th...
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Citations
... The relationships used to determine the mechanical properties based on the HV hardness of aluminium alloys have been adapted from [40] Taking into account the recrystallization effect of the aluminium alloy with the simultaneous strong reduction of grain size, their values were additionally determined according to the values of the correlation coefficients given in [41]: ...
The aim of this paper is to analyse the mechanical properties of butt joints between S355 steel and 6061-T6 aluminium alloy, as well as their relationship to changes in the structure of the material caused by welding. The effect of the tool offset was analysed in particular. For the analysis, tensile tests were carried out using macro-and mini-specimens taken from S355/AA6061-T6 joints and base materials. In addition, the macro-and microstructure of the joints was determined, the hardness profiles in the joints were analysed, and fractographic analysis of the fractures of the specimens was carried out. Based on the results of the macro-and microstructure examinations, typical friction stir welding (FSW) joint zones were characterised. The microstructure was observed in the interface line of the materials on the root side, the negative effect of which on the quality of the joint was confirmed by digital image correlation (DIC) strain analysis during the monotonic tensile test. The highest average value of su = 141 MPa for the entire joint was obtained for a 0.4 mm tool offset. The highest average value of su = 185 MPa for the selected joint layer was obtained for a 0.3 mm tool offset. Fracturing of the joint in the selected layer for the tool offset values of 0.3 mm and 0.4 mm occurred in the weld nugget zone (WNZ) where the lowest hardness was recorded.
... The variation ranges for each parameter are carefully considered following previous studies [45,46] to cover different types of aluminum alloys. These ranges are reported in Table 2. ...
This study presents a calibration method based on machine learning techniques to identify parameters of hardening law of aluminum alloy sheets in complex manufacturing processes. A V-shape test is designed to characterize material behavior during an incremental sheet forming (ISF) process. A series of virtual materials is first generated using three physical features observed in a standard uniaxial tensile test: initial yield stress, maximum uniform plastic strain, and yield-to-strength ratio. These virtual materials are then employed in simulating the designed V-shape tests to numerically collect the material responses, such as forming forces, displacements, or their combinations. Several feed-forward neural networks (FFNNs) are developed and trained to relate the collected material responses to the relevant virtual materials. Then, the trained FFNNs were used to estimate the flow curve of AA5052-H32 sheets up to a plastic strain value of 1.0 using the experimentally measured response from the V-shape test during ISF. The FFNN-based flow curves appear to capture well the stress–strain data obtained from the uniaxial tensile test with the coefficients of determination up to 0.98. The identified flow curves are also employed to simulate the uniaxial tensile and ISF truncated cone tests. The simulated uniaxial tensile forces are in good agreement with the experimentally measured results. A maximum difference of 5% is observed in the comparison between the simulated and measured ISF loading forces in the steady-state deformations. The comparisons demonstrate the efficiency of the proposed method to characterize the plastic flow of metal.
... In this study, the BM and WM were treated as if they were different alloys, related to their properties for hardness measurements. The used relationships for mechanical properties determination (ultimate stress σ u and yield stress σ y ), which are empirical equations often used for Al alloys and validated in previous studies [38], are reported in Equations (1) and (2): (1) and (2) are illustrated in Table 2 (welds A, B, and C are shown in Figure 1). To perform accurate nonlinear FE analyses, the values of σ y and σ u were used to achieve the static true stress-strain curves, based on the Ramberg-Osgood (R-O) equation. ...
The aim of this scientific work was to evaluate the compression instability effects during static and low-cycle fatigue loadings of AA 5083 welded joints, commonly used in marine structures. Low-cycle fatigue assessment in marine structures is of utmost importance since high levels of plastic deformation can arise in the proximity of high-stress concentration areas. Displacement ratios equal to minus one and zero were used to perform experimental low-cycle fatigue tests. The tests were monitored by means of the Digital Image Correlation technique in order to detect the strain patterns, with particular attention paid to stress concentration areas, indicating that a specimen tends to buckle during high compression loads, for tests with a displacement ratio of minus one. The tests at displacement ratios equal to −1 showed a lowering of the strain–life curve revealing a considerable effect on compression instability. A nonlinear finite element modelling procedure, depending only on hardness measurements, was developed. The hardness measurements were used in order to assess the distinct mechanical properties of the different zones that were included in the finite element model. The finite element model results were compared to the data achieved by means of the digital image correlation technique, demonstrating that hardness measurements can help predict the low-cycle fatigue behaviour of welded joints and consider compression instability phenomena.
... In general, the microhardness value of the zone far away from the welding zone was larger than that in the welding zone. Stathers et al. [22] found that microhardness could be used as a robust characterization tool to forecast as the yield strength (YS) and the ultimate tensile strength (UTS) The average microhardness of the as-cast billet was found to be 38 ± 3 HV0.5. It was found that the extrusion process improved the microhardness of the extruded profiles. ...
... In general, the microhardness value of the zone far away from the welding zone was larger than that in the welding zone. Stathers et al. [22] found that microhardness could be used as a robust characterization tool to forecast as the yield strength (YS) and the ultimate tensile strength (UTS) Figure 13. Microhardness of profile as a function of (a) ram speed, (b) average grain size. ...
... Stathers et al. [22] found that microhardness could be used as a robust characterization tool to forecast as the yield strength (YS) and the ultimate tensile strength (UTS) through experiments Figure 13b shows the microhardness value as a function of the inverse square root of grain sizes. The microhardness values exhibited a very reasonable linear relationship with the inverse square root of the grain sizes as evidenced by the Adj. ...
Extrusion experiments and 3D numerical modeling were conducted to investigate the dynamic recrystallization and welding quality of a 6063 aluminum alloy hollow square tube extruded by a porthole die at the ram speeds of 3 mm/s, 7 mm/s, 9 mm/s and 11 mm/s. The results showed that average grain size of hollow square tube extruded at the ram speed of 7 mm/s was the smallest. The profile extruded at the ram speed of 3 mm/s exhibited the highest expansion ratio. Dynamic recrystallization (DRX) fractions were highly variable at different ram speeds. DRX fractions in the matrix zones were higher than those in the welding zones, resulting in smaller grain sizes in the matrix zones. Mechanical properties in the welding zones and matrix zones was different. A local strain concentration would occurred during expansion, which would affect the welding quality. Finally, it was found that the uniform microstructure near the welding line would also affect the welding quality.
... Nevertheless, some components require to be joined by a fusion welding process. In these cases, the heat input from welding thermal cycle lead to a decrease between ~40 and ~50 % in the mechanical properties of these alloys in the heat affected zone (HAZ), depending on the heat input, owing to the transformation of the small needle shaped and coherent Mg 2 Si precipitates, β ′′ -phase, into the larger rod-shape partially coherent β ′ -phase and largest incoherent cube-like β-phase [9][10][11][12][13][14][15]. Additionally, in the fusion zone, porosity in the weld metal is prone to be formed as a result of the high solubility of hydrogen in molten aluminum [16,17]. ...
Plates of 6061-T6 aluminum alloy of 6.35 mm thick were welded by using the hybrid gas tungsten arc - gas metal arc welding process (GTAW-GMAW) and compare with the conventional gas metal arc welding (GMAW). An ER-5356 filler wire of 1.2 mm in diameter and argon of high purity as protective gas were used in both processes. The aim of the experiments was to assess the effects that yield the GTAW-GMAW welding process on the microstructure and the mechanical properties of the welded joints in the as weld and after artificial aging condition. Heat inputs were set up between ∼ 0.9 kJ/mm and ∼ 1.1 kJ/mm. Plots of the grain size and porosity ratio showed that GTAW-GMAW promoted a grain structure refinement and a reduction of porosity in weld metal. In addition, GTAW-GMAW indicate a reduction on the degradation in the heat affected zone in the as weld condition and a 40 % increase in welding speed. There was observed a major losing of magnesium in weld metal in the conventional GMAW process, this effect reflects on the final mechanical strength and microhardness of weld metal after artificial aging, as less Mg is available to get in solid solution.
... The contour lines originate from a fit of the simulated hardness data (circles). (b) Comparison between calculated hardness based on the results in Fig. 4 a) and the experimental hardness for commercially pure Ti ( ASM Aerospace Specification Metals ;Gupta et al., 2015 ) as well as 6061-T651 Al( Stathers et al., 2014 ), Co-W-C( Roebuck and Almond, 1984 ), Ti6Al4V ( ASM Aerospace Specification Metals ;Chen et al., 2015 ) and equiatomic fcc (high entropy) alloys( Wu, 2014 ). ...
The effect of geometric confinement is well-known from hardness measurements of thin films on stiff substrates and has been modeled both phenomenologically and using e.g. Finite Element Analysis. However, these models are mainly focused on a specific experiment or a certain material family. In the present work, Finite Element Analysis is used to gain a better understanding of the interplay between geometric constraints in various microstructures and a wide range of materials properties. It is shown that a very simple model can be used to replicate thin film hardness data where the film is softer than the substrate as well as how materials properties alter the indentation behavior of materials confined in one to three dimensions. It is shown that qualitative agreement with nanoindentation of the metallic binder phase in the complex 3D-microstructure of a cemented carbide is achieved using an axisymmetric “pill-box” model with classical plasticity. It is also shown that the effect of higher-order confinement can be described by the Korsunsky thin film hardness model by re-optimizing the fitting parameters.
... 34 Due to the application of thermal cycles at temperatures above 200 C, it causes reversion (dissolution) of strengthening b 00' -(Mg 2 Si) precipitates at HAZ and weld region. 10,35,36 Also, some of the b 00 transforms to b 0 on cooling, where the aspects of strength in b 0 is low in comparison to b 00 giving rise to declining microhardness. 37 The cumulative alloying elements content (wt.-%) of Mg and Si in base metal and filler wire was noted as 1.05% and 6.31%, respectively. ...
... However, the CMT weld region (59.78 HV) recorded better microhardness values and were in line with the previous investigations using MIG (52 HV) 35 and TIG (56 HV). 10 Similarly, in comparison with high efficiency welding process LBW (60 HV), 28 FSW (69 HV) 28 and EBW (70 HV), 38 the noted strength was promising. ...
Aluminium alloy 6061-T6 is utilized in aerospace industry for developing pressure vessel liner. Cold metal transfer is a promising welding process used in fabricating aluminium structures. The present work is focussed to achieve an optimum welding parameter for joining a 3.5-mm thick pressure vessel and to examine the mechanical properties and metallurgical nature of the weldment. The welded joint was evaluated as defect free using radiography test. The joint efficiency (66.61%) and measured microhardness of weldment (59.78 HV) exhibited promising results. The effect of grain coarsening in the heat affected zone (HAZ) and weld zone is attributed to the thermal gradients during welding. Dissipation of small amounts of strengthening elements Si and Mg during welding leads to reduction in mechanical properties. X-ray diffraction peaks revealed the presence of intermetallic Al–Si and Fe–Si in the weld zone. Fractography examination confirms the ductile type of failure in the fractured surface of the tensile samples.
... The strength reduction experienced in the welded joints of aluminum alloys limits their application to lightweight structures (Refs. 1,2). For heat-treatable aluminum alloys, the strength reduction is mainly due to the loss of the precipitation hardening effect in the fusion zone (FZ) and heataffected zone (HAZ) (Ref. ...
Three different heat treatment sequences, which alter
the solute redistribution state in as-welded (AW) Aluminum Alloy 6061 resistance spot welds, were designed to
investigate the effect of welding-induced microsegregation on the bake-strengthening ability of the joints. These
sequences were postweld baking (AW-B), preweld solution
treatment and postweld baking (SW-B), and postweld solution treatment and baking (WS-B). Vickers hardness and
lap-shear test results showed that, compared with the AW
samples, both the AW-B and SW-B samples experienced
limited weld strengthening, while the WS-B sample welds
experienced significant strengthening after baking (the
strength was found to be comparable to that of the base
metal). Calculation of the solidification path in the fusion
zone using the Scheil-Gulliver model showed the effective
solutes (Mg and Si) are segregated at the interdendritic regions in the AW samples (to form the β-Mg2Si phase and
eutectic), as confirmed by transmission electron microscopy. This reduced the degree of solute supersaturation, thereby significantly weakening the bake-strengthening ability of this site. Only the postweld solution treatment, which caused the effective solutes to diffuse into
the Al-rich dendrites, could make the bake-hardening ability of the weld comparable to that of the base metal (confirmed by scanning transmission electron microscopy). Finally, digital image correlation analysis was conducted on
a specially designed lap-shear test sample to reveal the
local strain in the joints. It was found that, for the same
weld size, the strain concentration occurred in the fusion
zone of the AW and AW-B samples, and at the load-bearing site in the base metal of the SW-B and WS-B samples.
Thus, the application of postweld solution treatment could
improve the bake-strengthening ability of Aluminum Alloy
6061 resistance spot welded joints and increase the tendency of the joints to experience pullout failure.
... Contribution of alloying elements (Cu, Zn etc.) of base materials to weld pool may maintain the mechanical properties of the weld metal although the grain coarsening. Stathers et al. [16] have reported that the dilution of the weld filler metal (4043) by 6061 base material affects the mechanical properties of the weld. Nevertheless, excess heat input increased the dendrite arm spacing, porosity (Fig. 1), and microsegregation, which causes the abrupt drop in hardness especially in the weld metal of 67-H. ...
Cold Metal Transfer (CMT) welding provides many advantages for welding of dissimilar materials and thin sheets with its superior heat input control mechanism. In present study, AA6061 and AA7075 aluminium alloys were joined with CMT welding. The effect of welding parameters on hardness, tensile strength and corrosion rate was investigated. Tafel extrapolation method was carried out to determine the corrosion rates of AA6061 and AA7075 base metals and AA6061-AA7075 joints. Increasing heat input was found to be detrimental for both mechanical properties and corrosion resistance. The outcomes showed that CMT welding produces adequate joints of AA6061-AA7075 in terms of mechanical properties and corrosion resistance, favourably with welding parameters which provide low heat input.
... The influence of the different materials was considered. The tensile properties of the materials were calculated from hardness measurements, according to the procedure reported in [6,15,17], in order to perform a non-linear FE analysis, and the FE results were validated by means of the experimental data obtained through the Digital Image Correlation technique. Two full-field techniques were applied: the Digital Image Correlation technique (DIC) for the displacement field detection and the Infrared Thermography (IRT) to monitor the surface temperature of the specimen. ...
