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This paper deals with the selection of the optimal material for railway wagons, from among three different steel and three aluminium based materials, by using four different Multicriteria Decision Making Methods (MCDM) and comparing their ranking of the materials. We analysed: Dual-Phase 600 steel, Transformation-Induced Plasticity (TRIP) 700 steel, Twinning-Induced Plasticity (TWIP) steel, Aluminium (Al) alloys, Al 6005-T6, and Al 6082-T6, and porous Al structure with closed cells. Four different MCDM methods were used: VIKOR, TOPSIS, PROMETTHEE and the Weighted aggregated sum product assessment method (WASPAS). Key material properties that were used in the MCDM analysis were: density, yield strength (Y.S.), tensile strength (T.S.), Y.S./T.S. ratio, Youngs modulus (Y.M.), cost and corrosion resistance (C.R.). Research results indicate that aluminium and its alloys prove to be the most suitable material, based on setup criteria. Advanced steels also achieved good ranking, making them a valid option, immediately behind lightweight aluminium alloys. Porous aluminium did not perform well, according to the used MDCM methods, mainly due to the significantly lower strength exhibited by the porous structures in general.

Advanced high-strength steels (AHSSs) are designed for meeting strict requirements, especially in the automotive industry, as a means to directly influence the reduction in the carbon footprint. As rotary friction welding (RFW) has many important advantages over other welding technologies, it plays an important role in the automotive sector. On the above basis, in this work, combinations of the first (complex phase (CP)), second (TWIP (TW)), and third (quenched and partitioned (Q&P)) generations of similar and dissimilar high-alloyed advanced steels have been joined by the RFW process. Having a specific microstructure, rods of CP/CP, Q&P/Q&P, CP/TW, and Q&P/TW steels were welded by employing a homemade adaptation machine under fixed parameters. Microstructural characterization has allowed us to corroborate the metallic bonding of all the tested advanced steels and to identify the different zones formed after welding. Results indicate that the welding zone widens in the center of the workpiece, and under the current friction action, the intermixing region shows the redistribution of solute elements, mostly in the dissimilarly welded steels. Furthermore, because of their complex chemistry and the different mechanical properties of the used steels, dissimilarly welded steels present the most noticeable differences in hardness. The TWIP steel has the lower hardness values, whilst the CP and Q&P steels have the higher ones. As a direct effect of the viscoplastic behavior of the steels established by the thermomechanical processing, interlayers and oxidation products were identified, as well as some typical RFW defects. The electrochemical response of the welded steels has shown that the compositional and microstructural condition mostly affect the corrosion trend. This means that the dissimilarly welded steels are more susceptible to corrosion, especially at the TWIP–steel interface, which is attributed to the energy that is stored in the distorted microstructure of each steel plate as a consequence of the thermomechanical processing during RFW.

The corrosion behavior of austenitic Fe–Mn–Al–Cr–C twinning-induced plasticity (TWIP) and microband-induced plasticity (MBIP) steels with different alloying elements ranging from 22.6–30 wt.% Mn, 5.2–8.5 wt.% Al, 3.1–5.1 wt.% Cr, to 0.68–1.0 wt.% C was studied in 3.5 wt.% NaCl (pH 7) and 10 wt.% NaOH (pH 14) solutions. The results obtained using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques, alongside optical microscopy analysis, revealed pitting as the dominant corrosion mechanism in high-Mn TWIP steels. An X-ray diffraction analysis of the surface revealed that the main corrosion products were hematite (Fe2O3), braunite (Mn2O3), and hausmannite (Mn3O4), and binary oxide spinels were also identified, such as galaxite (MnAl2O4) and jacobsite (MnFe2O4). This is due to the higher dissolution rate of Fe and Mn, which present a more active redox potential. In addition, a protective Al2O3 passive film was also revealed, showing enhanced corrosion protection. The highest corrosion susceptibility in both electrolytes was exhibited by the MBIP steel (30 wt.% Mn). Pitting corrosion was observed in both chloride and alkaline solutions.

The effect of strain rate on the work-hardening behavior of high-manganese twinning-induced plasticity (TWIP) steel has been investigated. The influence of adiabatic heating and deformation rate on the mechanical properties was studied by quasi-static and dynamic tensile tests with synchronous temperature and strain measurements. TWIP steel has excellent strain-hardening behavior under both quasi-static and dynamic loading conditions. Strain rate has negligible effects on yield and tensile strength, but the uniform and total elongation decreases under dynamic tests. TWIP steel has excellent energy absorption (EA) capacity of above 55 kJ/kg at all strain rates compared to dual-phase steels, transformation-induced plasticity steel and ferritic steels. However, the EA of TWIP steel is slightly lower compared to austenitic stainless steels. A rise in temperature due to adiabatic heating has led to the increase of stacking fault energy, thereby resulting in a change of twinning behavior or the promotion of dislocation glide under dynamic loading.

Hydrogen embrittlement behaviors of a 22Mn–0.6C (mass%) twinning induced plasticity (TWIP) steel with the grain sizes of 21 μm (coarse grain) and 0.58 μm (ultrafine grain) were investigated by means of hydrogen precharging and subsequent slow strain rate tensile tests. The total elongation and fracture stress for both of the coarse-grained and ultrafine-grained specimens decreased by hydrogen charging. The area fraction of the brittle fracture surfaces in the ultrafine-grained specimen was much smaller than that in the coarse-grained specimen. Three-point bending test also showed that the reduction of the fracture toughness by the introduction of hydrogen was much smaller in the ultrafine-grained specimen than that in the coarse-grained specimen. It was concluded that the suppressed hydrogen embrittlement by grain refinement in the 22Mn–0.6C TWIP steel was probably due to the smaller hydrogen contents per unit grain boundary area in the finer grain-sized material.

The plastic deformation of TWIP steel is greatly inhibited during the expansion process. The stress–strain curves obtained through expansion experiments and observations of fracture morphology confirmed the low plastic behavior of TWIP steel during expansion deformation. Through an analysis of the mechanical expansion model, it was found that the expansion process has a lower stress coefficient and a faster strain rate than stretching, which inhibits the plasticity of TWIP steel during expansion deformation. Using metallographic microscopy, transmission electron microscopy, and EBSD to observe the twin morphology during expansion deformation and tensile deformation, it was found that expansion deformation has a higher twin density, which is manifested in a denser twin arrangement and a large number of twin deliveries in the microscopic morphology. During the expansion deformation process, dislocation slips are hindered by twins, the free path of the slips is reduced, and dislocations accumulate significantly. The accumulation area is the initial point of crack expansion. The results show that the significant dislocation accumulation caused by the delivery of a large number of twins under expansion deformation is the main reason for the decrease in the plasticity of TWIP steel.

High-Mn steels are widely used in various fields. However, the FCC structure is not conducive to improving strength, limiting their development and application. In this work, hot-rolled Fe-25Mn-1Al-3Si-1C (wt.%) steel was annealed at various temperatures to tailor the cementite particles and recrystallized grains, thus achieving a balance between strength and ductility. As the annealing temperature increased from 550 to 650 °C, the volume fraction of recrystallized grains slightly increased and the volume fraction of cementite particles initially increased and then decreased, which was explained and verified by the quantitative calculation. Especially, the high-density pre-dislocation and finely dispersed cementite particles in sample AN550 resulted in a relatively low volume fraction of recrystallized grains. Interestingly, secondary deformation twinning was activated during the subsequent tensile deformation in addition to the dislocations, stacking faults, and previous deformation twinning. This complex interaction among various deformation mechanisms indued a good balance between strength and ductility, achieving an outstanding result (58.9 GPa%) regarding tensile strength and total elongation. This work offers an effective route for developing a high-Mn TWIP steel with outstanding strength–ductility balance.

Microstructure, texture and mechanical property of Fe-27Mn-3Si-4Al TWIP steels during asymmetric warm rolling were studied. It was found that asymmetric warm rolling strongly refined the microstructures and affected texture evolution of steels because of an additional shear strain in contrast to the symmetric warm rolling. The complete recrystallization occurred on the upper and central layer of sheet, and Goss and Brass textures was developed into γ-fiber and R-Copper {112}   textures when the velocity ratio increased to 1.2. The combination of applied asymmetry rolling at elevated reduction resulted in a high yield strength (706 MPa) due to the enhanced shear deformation on the one hand and a reasonably high elongation (26.3%) on the other hand which was attributable to the grain fragmentation at higher velocity ratio, while the significant enhancement of ductility (30.9%) was achieved by the higher dislocation activation due to the decrease of rolling reduction.

Grain size is a microscopic parameter that has a significant impact on the macroscopic deformation behavior and mechanical properties of twinning induced plasticity (TWIP) steels. In this study, Fe-18Mn-1.3Al-0.6C steel specimens with different grain sizes were first obtained by combining cold rolling and annealing processes. Then the influence of grain size on the plastic deformation mechanisms was investigated by mechanical testing, X-ray diffraction-based line profile analysis, and electron backscatter diffraction. The experimental results showed that the larger grain size could effectively promote twinning during plastic straining, produce an obvious TWIP effect, and suppress the rate of dislocation proliferation. The continuous contribution of dislocation strengthening and twinning functions led to a long plateau in the work-hardening rate curve, and increased the work-hardening index and work-hardening ability. At the same time, the strain could be uniformly distributed at the grain boundaries and twin boundaries inside the grain, which effectively relieved the stress concentration at the grain boundaries and improved the plasticity of deformed samples.

This study investigated the stress–strain behavior and microstructural changes of Fe-Mn-Si-C twin-induced plasticity (TWIP) steel cylindrical components at different depths of deep drawing and after deep drawing deformation at various positions. The finite element simulation yielded a limiting drawing coefficient of 0.451. Microstructure and texture were observed using a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The research revealed that the extent of grain deformation and structural defects gradually increased with increasing drawing depth. According to the orientation distribution function (ODF) plot, at the flange fillet, the predominant texture was Copper (Cu)112 orientation; at the cylinder wall, the main textures were Copper Twin (CuT) and Goss (G) orientations; at the rounded bottom corner of the cylinder, the primary texture was τ-fiber ( //TD), with its strength increasing with deeper drawing.