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The article present the results of the study on the improvement of mechanical properties of the surface layer of 7075 aluminum alloy via two-stage aging combined with shot peening. The experiments proved that thermo-mechanical treatment may significantly improve hardness and stress distribution in the surface layer. Compressive stresses of 226 MPa±...
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... The basic machining parameters that have a decisive impact on shaping the geometry of the cutting gap include the water pressure, the traverse speed of the cutting head, the type and abrasive flow rate, the diameter and length of the focusing tube, stand-off distance, which they described, among others: Zhu et al., who described the process of cutting wood [21] and Aydin et al., who described the use of waste produced following the cutting of solid granite as an alternative abrasive in the water jet cutting of marble [22]. This process was also described by Kaczmarek, who wrote that the treatment of materials with a high-pressure water jet is a complex process [23]. To cut any material and to increase the efficiency of the process, dry natural abrasives such as garnet and olivine or synthetic abrasives (broken glass, aluminum oxide) are added to the jet [24]. ...
The use of selected multi-criteria decision methods for the optimization of cutting processes by abrasive water jet methods is increasingly being used in industrial processes. This is due to the complexity of the processes and the need to reduce operating costs. Process optimization methods are available to support organizational processes including the design phase, quality assurance, production automation, and many more. This article presents the current state of research on the water-abrasive cutting process and the use of multi-criteria methods in optimizing this process. This article presents a detailed methodological study of the VIKOR approach to optimization, indicating the applicability conditions, assumptions, and limitations on the example of high-pressure abrasive water jet cutting of elements made of titanium alloy utilizing HPX garnet abrasive. As a result of the research conducted, the best input parameters of the cutting process for abrasive flow rate, pressure, and the traverse speed of the cutting process were determined. The achieved result is consistent with the assumption that the most favorable output parameters are the highest cutting depth and the lowest level of roughness.
... On the other hand, G. Lütjering also showed how Fe has an inhibitory effect on the grain growth of titanium alloys at the micron grain scale after comparing two different Fe levels (0.15% and 0.03%) [25]; however, the study of the Fe alloying effect on the thermal stability of a UFG/NC titanium alloy is rarely reported. Considering that post-annealing is a common method used to optimize the microstructure and mechanical behavior of deformed and welded materials [26][27][28][29][30], as well as to fix the issue of thermal stability of the UFG/NC materials mentioned above, it is interesting to study the effect of heat treatment on the microstructure and mechanical behavior of the UFG/NC Ti-2Fe-0.1B alloy. ...
In the present study, a novel Ti-2Fe-0.1B alloy was processed using equal channel angular pressing (ECAP) via route Bc for four passes. The isochronal annealing of the ultrafine-grained (UFG) Ti-2Fe-0.1B alloy was conducted at various temperatures between 150 and 750 °C with holding times of 60 min. The isothermal annealing was performed at 350–750 °C with different holding times (15 min–150 min). The results indicated that no obvious changes in the microhardness of the UFG Ti-2Fe-0.1B alloy are observed when the annealing temperature (AT) is up to 450 °C. Compared to the UFG state, it was found that excellent strength (~768 MPa) and ductility (~16%) matching can be achieved for the UFG Ti-2Fe-0.1B alloy when annealed at 450 °C. The microstructure of the UFG Ti-2Fe-0.1B alloy before and after the various annealing treatments was characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). It was found that the average grain size remained at an ultrafine level (0.91–1.03 μm) when the annealing temperature was below 450 °C. The good thermal stability of the UFG Ti-2Fe-0.1B alloy could be ascribed to the pinning of the TiB needles and the segregation of the Fe solute atoms at the grain boundaries, which is of benefit for decreasing grain boundary energy and inhibiting the mobility of grain boundaries. For the UFG Ti-2Fe-0.1B alloy, a recrystallization activation energy with an average value of ~259.44 KJ/mol was analyzed using a differential scanning calorimeter (DSC). This is much higher than the lattice self-diffusion activation energy of pure titanium.
... Because as many other manufacturing methods due to a lot of control parameters and its vast range of changes, require optimization carried out to achieve the desired effects, for example different chemical synthesis [8], [9], [10], [11] military [12], automotive [13], [14] or treatment heavy to machining materials [15], [16], [17]. In the case of more than one starting criterion, which additionally hinder the analysis especially for mutually opposing effects, multi response optimizations should be used [18], [19], [20]. ...
The paper presents the results of the optimization of high-speed Abrasive Water Jet (AWJ) machining. The complexity of the problem, conditioned by mutually opposite parameters: maximal cutting depth and minimal surface roughness is the reason for using the Response Surface Method (RSM) optimization methods. The three most influencing parameters were subjected to the process: process pressure, abrasive flow rate, and traverse speed. Based on RSM and analysis of variance, the machining model in the form of a full quadratic equation was formulated. To estimate multicollinearity, the variance inflation factor (VIF) was examined. A set of optimal control parameters was determined based on the composite desirability function. The description of the conducted research and the results of the verification were proving the high accordance of models with experimental data.
... The size and distribution of proeutectic silicon can be improved by addition of (i) Na, P, Sr, (ii) rare earth metals, (iii) hard ceramic reinforcement followed by mechanical stirring of the alloy [5,6]. Moreover, heat treatment followed by aging process, and thermomechanical processing of the alloy also help in the refinement process [7]. One of the most economical method to improve the wear resistance of hyper-eutectic Al-Si alloys is achieved by reinforcing ceramic minerals. ...
In this work, high temperature wear-resistant LM30/sillimanite composites for automotive applications have been fabricated. Dual particle size composites reinforced with naturally occurring sillimanite mineral were processed and investigated for operating temperatures in the range of 50–300 . Sillimanite particles with size range of 1–20 μm (fine) and 75–106 μm (coarse) were mixed in weight ratio of 3:1, 1:1, and 1:3 to be reinforced to the LM30 alloy. SEM micrographs and area mapping/line mapping profile results showed presence of different phases and revealed that sillimanite inclusion changed the morphology of proeutectic silicon to globular and refined its grain size. Particles were well distributed in LM30 matrix. Increase in reinforcement level of particles led to continuous improvement in properties. As such, the best properties were obtained in composite containing 15 wt% sillimanite with proportion of fine: coarse particles as 3:1 (15-DPS3 composite). The transition temperature of wear mode increased from 150 for base alloy to 200 for composites. For the temperature-pressure condition of 200–1 MPa, 15-DPS3 composite showed 15% higher hardness, 80% lower wear rate, 48% lower friction coefficient, and 28% lower thermal expansion coefficient than base alloy. These wear characteristics of composites were comparable to the commercially used grey cast iron material. XRD of wear track/debris confirmed the formation of tribolayer. SEM analysis of wear track/debris identified the wear mechanisms causing materials loss under different contact pressures. Light-weight and economical composites developed in this research can act as a good substitute for the heavy cast iron components used in industry.
... 7XXX serials (Al-Zn-Mg-Cu) aluminum alloys have been widely used in Aeronautics and Astronautics industries over the past decades mainly by virtue of their ultrahigh strength and low density [1,2]. In general, the high strength of the alloys can be facilely achieved in the following ways: i) Modified surface techniques [3][4][5][6]. ii) Optimized nanoscale precipitates in Al matrix [2]. iii) Refinement grain sizes [7,8] in ultrafine-grained (UFG) and nanostructured (NS) aluminum alloys, which are both produced by severe plastic deformation [9][10][11][12] (SPD). ...
... Generally, the optimized surface treatment [6], high-number density of nano-size precipitates [55], refined microstructure [10,15] and high density of dislocation [17] are the main sources of materials strengthening. In the initial state (0 h), the hardness can be summarized as HV PA +RTR N HV RTR N HV PA N HV ST (Fig. 8a). ...
To clarify the influence of a pre-ageing treatment on precipitation behaviors in the AA7075 aluminum alloys with ultrafine grain (UFG) structure, the alloys were pre-aged prior to a room temperature rolling process (PA + RTR). The precipitation kinetics in PA + RTR alloys during isothermal heat treatment at 100 °C were systematically investigated by transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and Vickers hardness measurements compared to its counterpart without pre-ageing treatment (i.e. RTR). Results reveal the pre-ageing treatment can lead to a higher dislocation density (22.8 × 1014 m−2) and a larger concentration of Mg (~12.85 at.%) and Zn (~8.33 at.%) atoms in the vicinity of dislocation, which causes a considerable increase in the size and volume fraction of the precipitates in PA + RTR alloy. Specially, our study shows, for the first time, that many GPII zones come from second nucleating in PA + RTR alloy at 108 h, which may ascribe to the pre-ageing treatment. More importantly, the pre-ageing treatment not only makes both two hardness peaks of PA + RTR alloy appeared ahead of but also higher than those of RTR alloy, by virtue of the enhanced precipitation kinetics in PA + RTR alloy. Keywords: Ultrafine grain, Aluminum alloys, Precipitation kinetics, Pre-ageing treatment, Small angle X-ray scattering, Microstructure analysis
... Many researchers have worked on improving the properties of Al alloy with ceramics, particulates, metal powders and even thermo-mechanical treatments. For instance, Ehsan et al [7] reinforced Al alloy with TiC, Loto and Babalola [8] improved Al with SiC using SPS, Zawadzki et al [9] improved AA7075 alloy with heat treatment and shot penning, and Kyziol et al [10] surface-modified AA2024 by chemical vapour deposition. However, SPS of Al-CNTs-Nb composite aimed at improving the wear characteristics of Al alloy has not been reported anywhere in the literature despite the excellent properties of these reinforcements. ...
Unreinforced Al alloy lacks adequate tribological property required in service. To improve on this property, it must be reinforced with materials having good wear properties. Hence, Al was reinforced with CNTs and Nb and consolidated with spark plasma sintering (SPS). The wear experiment was conducted on a ball-on-disc Tribometer where loads of 10 N, 20 N and 30 N were systematically applied. The coefficients of friction (COF) of the sintered samples were subsequently obtained. The samples were weighed before and after each run to determine their weight losses which were used to compute their wear volumes. The experiment was designed and analyzed with Taguchi and ANOVA. Results showed that Al-8CNTs-8Nb composite had the best wear characteristics. Its COF got improved by 79% which shows that it is suitable for industrial applications.
... The influences of different machined notches were then discussed in terms of the fatigue limit of FOD-affected turbine blades by using the critical distance [7]. To increase the fatigue limit of FOD-affected specimens, surface peening was tentatively adopted [7][8][9][10][11]. The fatigue crack initiation site was clearly observed inside the material rather than at the peened notch root [1]. ...
Various surface defects of high-speed railway lightweight hollow axles made of alloy steel were identified carefully for assessing its operation safety and reliability. Three types of foreign object damages (FOD) from compressed-gas gun device were defined as the corner, edge and plane defects in terms of defect geometry, respectively. The fatigue probabilistic S-N (P-S-N) curves and fatigue limits were acquired for smoothed and FOD-affected specimens. In view of the variations of size and roughness between the full-scale axles and specimens, the fatigue properties with three defect types were then modified for full-scale axles. The probabilistic Kitagawa–Takahashi diagram widely used for assessing the FOD in aero-engine was well transferred to the damaged railway axles. The fatigue limits of an FOD-affected axle with 95% confidence level and 95% reliability level were evaluated to replace that of smoothed specimens, which was suggested to assess the reliability of a damaged axle at the presence of FOD generated at a prospective higher operation speed.
... These materials have the greatest use in aerospace and automotive industries. Moreover, parallel to development of new materials, the new methods and techniques of their manufacturing and treatment are under continuous development [24,[28][29][30][31][32][33][34][35][36][37]. As a result, light alloys gain wider spectrum of applications, including those for elements working in friction couples. ...
Purpose: Low friction nc-WC/a-C:H coatings deposited by means of magnetron sputtering provide very good tribological properties in friction couple against hard steels and good adhesion to steel substrates. Nevertheless, it was necessary to elaborate a new type of coatings because the nc-WC/a-C:H one had no use in friction couple against aluminium alloys. Design/methodology/approach: In the paper the WC/a-C:H and (Si, Cr)C/a-C:H coatings were investigated. The coatings were investigated by means of SEM, EDS, in order to obtain thickness, surface morphology and chemical composition of coatings. Tribological properties of deposited coatings were elaborated by means of 'pin-on-disc' method in friction couple against 100Cr6 bearing steel and AlSi alloy. Findings: It was stated that (Si, Cr)C/a-C:H coatings have very good tribological properties in friction couple against bearing steel and AlSi alloy (friction coefficient <0,1). In case of WC/a-C:H coatings, good tribological properties were achieved in friction couple with bearing steel. Both coatings have very low wear rate in investigated friction couples. Research limitations/implications: The (Si,Cr)C/a-C:H coating have a worse quality of adhesion to quenched and tempered Vanadis 23 HS steel substrate in comparison with the nc-WC/a-C:H coating. Resolving this disadvantage can increase potential of application of (Si, Cr)C/a-C:H coatings. Practical implications: Newly developed (Si, Cr)C/a-C:H coating has a greater application potential for modification of surfaces of elements working in friction couples against hardened steels and light alloys like AlSi. Originality/value: There are numerous publications where low friction carbon based coatings were described mostly as a coatings deposited on elements working in friction couples against hard steels. Undertaken tests showed that the newly developed (Si,Cr)C/a- C:H coating can have a broad spectrum of applications in friction couples against different counterbodies, including light Al alloys.
The interlayer adhesion strength between nickel‐aluminum bronze (NAB) and epoxy coating and the corrosion resistance of the coating were investigated. The surface state of NAB with sandpaper abrasion, machining, and sandblasting is observed through laser confocal microscope. The pull‐off test measures the interlayer adhesion strength between the primer and the intermediate coating of different proportions. Electrochemical impedance spectroscopy (EIS) evaluate the corrosion resistance of the single‐layer primer and the matching intermediate coating. Chemical bond composition and content of the composite coating at different positions are evaluated by X‐ray photoelectron spectroscopy (XPS). The results show that the interlayer adhesion strength between the substrate abraded by 40 mesh sandpaper and primer is the largest (18.1 MPa). When the ratio of bisphenol A epoxy resin to phenolic amine of primer is (2.40:0.70) and the ratio of bisphenol A epoxy resin to polyamide of intermediate coating is (3.00:0.34), the multiple interlayer adhesion strength is the largest (20.51 MPa). The atomic content of N–C=O (288.4 eV) in primer/intermediate coating interface is the highest amount of them, up to 1.91%. Compared with a single‐layer epoxy coating (|Z|0.01 Hz = 1.30 × 10⁸ Ω cm²), using matching coatings (|Z|0.01 Hz=2.06 × 10¹¹ Ω cm²) can improve the corrosion resistance of the coating.
The paper presents the optimization of the epoxidation process of crotyl alcohol on the Ti-MWW catalyst at atmospheric pressure, based on the Taguchi orthogonal array method. Shown are the influence of the most important process parameters, such a temperature, molar ratio of crotyl alcohol to H2O2, methanol concentration, Ti-MWW catalyst concentration and reaction time. The response functions characterizing epoxidation process were selectivity of transformation to 2,3-epoxybutan-1-ol with respect to reacted crotyl alcohol – S2,3EB1O/CA, conversion of crotyl alcohol CCA, yield of 2,3-epoxybutan-1-ol W2,3EB1O. Based on the calculated signal/noise ratios for individual parameters of the process, their impact on all output parameters was determined and optimal process conditions were determined to reach its the maximum. The empirical verification of this process was also performed by comparing both output parameters predicted and achieved in the tests. This method allows limiting the number of tests required to reach the wished test results, diminution the time needed course for their achievement, and at the same time their expenses.
