Twinning-induced Plasticity Steel Research Articles

Effect of Plastic Deformation on Thermal Properties in Twinning-Induced Plasticity Steel.

The effect of plastic deformation induced by wire drawing on thermal properties in twinning-induced plasticity (TWIP) steel has been investigated. The investigation on the relationship between thermal conductivity (k) and the microstructure in the drawn TWIP steel wire was systematically performed to accurately understand the behavior of the k of a metal during wire drawing. The yield and tensile strengths linearly increased with drawing strain owing to the deformation twins and dislocations that were generated during wire drawing. However, the total elongation sharply decreased with drawing strain. The linear thermal expansion coefficient of the TWIP steel exhibited a similar value regardless of drawing strain. The density decreased linearly with temperature, and it was independent of the drawing strain. k increased initially and then decreased after reaching its maximum value with increasing drawing strains. At a nominal drawing strain of 0.26, k increased compared with the state of hot rolling because the increase in k due to grain elongation was greater than the decrease in k due to dislocations generated during wire drawing. However, as the amount of drawing step increased further, the influence of dislocations on k increased more than that of grain elongation, causing k to decrease.

Effect of Rapid Cooling on Microstructure and Mechanical Properties in Friction Stir Welded Twin-Induced Plasticity Steel

Effect of Rapid Cooling on Microstructure and Mechanical Properties in Friction Stir Welded Twin-Induced Plasticity Steel

Improved yield strength-ductility synergy of a high Mn TWIP steel by grain refinement and partial recrystallization

The industrial application of high Mn twinning-induced plasticity (TWIP) steels is limited by their low yield strength (YS). In this work, a combination of grain refinement and partial recrystallization was applied to increase the YS of a high Mn TWIP steel to 1215 MPa, along with a total elongation (TE) of 16 %. The high YS of the partially recrystallized steel mainly originates from the combination effect of high dislocation density up to 8.3 × 1014 m−2, fine grain size of about 1 μm in recrystallized regions, and dense mechanical twins with a small spacing of about 20 nm in unrecrystallized regions. This work provides a potential way to improve the YS-ductility synergy and broaden the application of TWIP steels.

Enhanced Mechanical Properties of Ceramic Rod-Reinforced TWIP Steel Composites: Fabrication, Microstructural Analysis, and Heat Treatment Evaluation

This study investigates the development and characterization of ceramic rod-reinforced TWIP (twinning-induced plasticity) steel matrix composites, produced using the lost foam casting technique. Mechanical tests revealed a substantial improvement in both flexural strength and ductility, with the composite demonstrating more than double the strength of unreinforced TWIP steel. Furthermore, a simple low-temperature heat treatment further enhanced these properties, increasing the flexural strength of the composite to 1023 MPa while also improving its ductility. The improvement in mechanical performance is attributed to the formation of additional twins in the TWIP steel matrix during deformation following heat treatment, which resulted in further strengthening of the matrix.

Influence of Ceramic Size and Morphology on Interface Bonding Properties of TWIP Steel Matrix Composites Produced by Lost-Foam Casting

This study investigated the fabrication and characterization of large ceramic-reinforced TWIP (twinning-induced plasticity) steel matrix composites using the lost-foam casting technique. Various ceramic shapes and sizes, including blocky, flaky, rod-like, and granular forms, were evaluated for their suitability as reinforcement materials. The study found that rod-like and granular ceramics exhibited superior structural integrity and formed strong interfacial bonds with the TWIP steel matrix compared to blocky and flaky ceramics, which suffered from cracking and fragmentation. Detailed microstructural analysis using scanning electron microscopy (SEM) and industrial computed tomography (CT) revealed the mechanisms influencing the composite formation. The results demonstrated that rod-like and granular ceramics are better for reinforcing TWIP steel composites, providing excellent mechanical stability and enhanced performance. This work contributes to the development of advanced composite structures with potential applications in industries requiring high-strength and durable materials.

Simultaneously enhancing the strength and ductility of Fe–Mn–C twinning-induced plasticity steel via Cr/N alloying

The effect of Cr/N alloying on the tensile deformation behavior of Fe–Mn–C twinning-induced plasticity steel was investigated through monotonic tensile tests, X-ray diffraction, electron back-scattered diffraction, transmission electron microscopy, and digital image correlation technique. The results demonstrate that the addition of Cr/N significantly enhances both the strength and ductility of Fe–18Mn-0.6C steel while dynamic strain aging (DSA) behavior weakens or even disappears. Compared with that in the Fe–18Mn-0.6C steel, more densely-spaced, thinner deformation twins were formed in the Cr/N-alloyed steel. Moreover, the Cr/N additions promote deformation twins to form over a wider strain range. This unique twinning behavior leads to a sustained high strain-hardening rate at higher strains, thereby delaying plastic instability and concurrently enhancing strength and ductility.

Machine-Learning-Assisted Composition Design for High-Yield-Strength TWIP Steel

Twinning-induced plasticity (TWIP) steel is an ideal material for impact-resistant structures and energy absorption because of its high product of strength and elongation. However, compared with other advanced high-strength steels, the relatively low yield strength of TWIP steel is one of the important shortfalls that significantly limits its engineering applications. To enhance the comprehensive properties of TWIP steel, a machine learning design strategy that integrated comparative modelling, SHAP analysis, and multi-objective optimization were adopted in this study. Initially, various machine learning algorithms were compared for their predictive accuracy based on normalized data (273 entries) regarding the microstructure and properties of TWIP steel. Then, performance prediction models for yield strength, tensile strength, and elongation were established. SHAP analysis was subsequently employed to assess the significance and explicit laws of composition and microstructures in these three target properties, identifying key elements that enhance the overall performance. Furthermore, two new TWIP steels with high yield strengths and high products of strength and elongation were developed via multi-objective optimization. Under conventional hot forging + hot rolling + cold rolling + annealing processes, the two designed TWIP steels had yield strengths of 585 MPa and 560 MPa, tensile strengths of 1055 MPa and 1101 MPa, elongations of 55% and 58.5%, and products of strength and elongation of 58.0 GPa% and 66.4 GPa%, respectively. The yield strengths of the designed TWIP steels significantly improved while maintaining a reasonable product of strength and elongation. This work provides important references for the rational development of new TWIP steels.

Microstructural Evolution and Hot Deformation Behavior of Cu‐Containing Twinning‐Induced Plasticity Steel

High manganese twinning‐induced plasticity (TWIP) steels with excellent strength and plasticity have promising applications in automotive manufacturing, but limited corrosion resistance affects their further development. Alloying with Cu is a viable solution to improve corrosion resistance. However, there remains a paucity of research concerning the effect of Cu on the hot deformation behavior of TWIP steels. So, the investigation of the recrystallization behavior and microstructural evolution in Fe‐23Mn‐6Cr‐3Al‐0.2C‐xCu (x = 0, 2.5) TWIP steels has been conducted using uniaxial hot compression test. The results reveal that Cu alloying exerts minimal influence on the high‐temperatur flow behavior, with dynamic recrystallization emerging as the predominant softening mechanism in Cu‐containing TWIP steels. However, owing to the drag effect of solute atoms, Cu alloying increases the activation energy for hot deformation and marginally reduces hot workability. Fine recrystallized grains in Cu‐containing TWIP steels can be achieved by hot deformation at lower temperatures and strain rate regions. The recrystallization behavior of Cu‐containing TWIP steels hot deformed at low temperatures and high strain rates is obviously inhibited by the increase of the activation energy and stacking fault energy, coupled with the hindering effect of Cu solute atoms clustered at grain boundaries on grain boundary migration.

Microstructure Evolution and Recrystallized Behavior of Friction Stir Welding Twin-Induced Plasticity Steel

Microstructure Evolution and Recrystallized Behavior of Friction Stir Welding Twin-Induced Plasticity Steel

Microstructures and mechanical properties of additively manufactured Fe–30Mn–3Al–3Si TWIP steel using laser powder bed fusion

Twinning induced plasticity (TWIP) high manganese steel demonstrates high ultimate tensile strength (UTS) and ductility, but its low yield strength limits its applications. This study presents the additive manufacturing of Fe–30Mn–3Al–3Si TWIP steel using laser powder bed fusion (LPBF) with enhanced mechanical properties. The average grain size of the LPBF-fabricated Fe–30Mn–3Al–3Si was 5.4 ± 1.3 μm, which was only one-tenth of that of a wrought one. In-situ formed Al-rich oxide nanoparticles were observed to be uniformly distributed in the matrix. The size of the oxide nanoparticles was about 30 nm with a volume fraction of about 0.9 %. The tensile yield strength was 554 ± 3 MPa and the UTS was 837 ± 7 MPa with an elongation of 41.5 ± 2.6 % for horizontal direction. Low anisotropy was observed for LPBF-fabricated Fe–30Mn–3Al–3Si. Compared with the wrought Fe–30Mn–3Al–3Si, the yield strength was increased by 140 %. This work provides a benchmark for the additive manufacturing of high manganese steel.

Improving strength-ductility synergy of twinning-induced plasticity steel by introducing a sandwich structure via submerged double-face friction stir processing

Twinning-induced plasticity steels typically exhibit remarkable plasticity and ultimate tensile strength, but the inferior yield strength has become a bottleneck limiting their application. In this work, a unique gradient sandwich structure that aims to break the bottleneck was successfully fabricated using a submerged double-face friction stir processing technique. The sandwich structure is composed of a coarse-grained zone in the core and two ultrafine-grained zones on the surfaces. An ultrahigh yield strength (1215 MPa) which is 2.2 times that of the as-received base material (543 MPa) is achieved for the sandwich structure. Additionally, significant elongation (19 %) and corrosion resistance are retained simultaneously. The coordinated deformation and effective strain transfer between the ultrafine-grained zones and coarse-grained zone facilitate the dispersion of stress and uneven deformation, which contributes to the excellent strength-ductility of the sandwich structure. This work provides a feasible method for fabricating high-performance steels.

Effect of friction stir welding with different heat input on microstructure evolution, mechanical properties and deformation behavior of twin-induced plasticity steel

The effect of friction stir welding (FSW) with different heat input on microstructure evolution, mechanical properties and deformation behavior of twin-induced plasticity steel was investigated in this paper. The results show that compared to the basal material (BM), the grain size in the stir zone (SZ) of FSW joint with low heat input was refined, and a large amount of deformation twins was formed. The grain was refined and numerous dislocations were formed in the stir zone-heat affected zone (SZ-HAZ) interface. In the FSW joint with high heat input, the grain size in SZ increased, while no deformation twins were observed. A large number of fine equiaxed grains were formed in the SZ-HAZ interface, while the grains in HAZ coarsened. Compared to the BM, the tensile strength and yield strength of low heat input joint increased to 1108 MPa and 597 MPa, respectively, while the elongation decreased to 50.4%, resulting in a strength-elongation product of 92% of BM. The joint with high heat input experienced a decrease in tensile strength, yield strength, and elongation to 806 MPa, 465 MPa, and 22.8%, respectively, with a strength-elongation product of only 30% of BM. During the tensile deformation process, the plastic deformation in the low heat input joint was mainly concentrated in BM, followed by HAZ, while SZ exhibited minimum plastic deformation, and the tensile fracture occurred at zone between SZ and HAZ. In the high heat input joint, the maximum plastic deformation occurred in the SZ, with lower plastic deformation in BM and HAZ, and finally fractured at the SZ. The constrain effect of different micro-zones and hindrance effect of dislocations and fine grains were main responsible for the deformation behavior of low and high heat input joints.

Effect of post-weld heat treatment on microstructure and mechanical properties of twinning-induced plasticity (TWIP) steel joints

The effect of post-weld heat treatment on microstructure and mechanical properties of twinning-induced plasticity (TWIP) steel joints obtained by melting electrode inert gas-shielded welding (MIG welding) was systematic studied. A total of two post-weld heat treatment processes are proposed, i.e., post-weld annealing treatment (PWAT) with temperature/time of 1100 ℃/1 h and subsequent furnace cooling and post-weld solution treatment (PWST) with temperature/time of 1100 ℃/1 h and subsequent water quenching, which were compared with the case of post-weld non-treatment (PWNT). Following annealing treatment at 1100°C, the joint tensile strength dropped by 6.6 % (from 845.46 MPa to 789.85 MPa), while its elongation at break increased by 40.87 % (from 29.80 % to 41.98 %). The significant increase in plasticity was due to the significant elimination of weld stresses in the joints after annealing. Moreover, the stresses in the weld metal of the PWST joints were instead significantly elevated and the carbides were solidified, which resulted in the lower strength. When post-weld heat treatment was applied, the impact toughness of the joints was lower than when untreated. This was primarily due to the greater percentage of the low-angle grain boundaries and the precipitation of MC-type carbides. Consequently, post-weld annealing treatment was an effective method to further enhance the strong plasticity of new twinning-induced plastic steel joints.

Mechanical behavior of twinning-induced plasticity (TWIP) steel fibre reinforced cementitious composite under impact loading

Twinning-induced plasticity (TWIP) steel fibre is a supermaterial known for its outstanding impact resistance. This paper, for the first time, applied TWIP steel fibre to increase the impact resistance of cementitious composites. The mechanical properties behaviours of TWIP steel fibre-reinforced cementitious composites (T-SFRCC) were investigated and compared with conventional SFRCC with normal steel fiber. The fractal theory was utilized to analyze the deterioration of damage in various SFRCCs subjected to impact loads, displaying TWIP steel fiber could prevent the cracks propagation and fewer fractal dimension compared with others. Results demonstrate that T-SFRCC has comparable compressive strength to SFRCC while exhibiting higher flexural strength. When subjected to impact loading, T-SFRCC demonstrates markedly improved energy absorption and impact toughness, such as better impact force and displacement. Specifically, the energy absorption capacity of T-SFRCC can exceed five times that of SFRCC with corrugated steel fiber, particularly evident when the drop height reaches 1200 mm. The influences of different fiber types and hammer drop methods on the impact resistance of SFRCCs were also discussed, which can provide reference for TWIP steel fiber in the field of cementitious composite materials.

Microstructures and mechanical properties of additively manufactured Fe–21Mn-0.6C TWIP steel using laser powder bed fusion

Twinning induced plasticity (TWIP) high manganese steel exhibits high ultimate tensile strength (UTS) and ductility, but its low yield strength restricts its applications. This research presents a Fe–21Mn-0.6C TWIP steel with enhanced mechanical properties additively manufactured using laser powder bed fusion (LPBF). The average grain size of the LPBF-fabricated Fe–21Mn-0.6C was 17.1 μm in the vertical direction, which was a quarter of that of a wrought one. The tensile yield strength was 657 MPa and the UTS was 1089 MPa with an elongation of 47.9% for the vertical direction. Compared to the wrought Fe–21Mn-0.6C, the yield strength increased by 110%. The high strength of LPBF-fabricated Fe–21Mn-0.6C is primarily attributed to solution, grain boundary and dislocation strengthening. Serrations were observed in the stress-strain curves at the initial stage of deformation, showing large stress drops. In the annealed sample, serrations appeared at a later stage of deformation with little stress drops. This difference in serration phenomenon is attributed to the varying dislocation density in the two samples.

Effect of stacking-fault energy on dynamic recrystallization, textural evolution, and strengthening mechanism of Fe−Mn based twinning-induced plasticity (TWIP) steels during friction-stir welding

This study aims to elucidate the effect of stacking fault energy (SFE) on the microstructural evolution and related hardening mechanisms of Fe−18Mn−0.6C−(0 and 1.5)Al and Fe−30Mn−3Al−3Si (wt.%) twinning−induced plasticity (TWIP) steels during friction stir welding (FSW) using a high−resolution electron backscattered diffractometer. With increasing SFE, the intensities of the Goss, CuT, and Brass components increased via active dynamic recrystallization (DRX) accompanied by twinning. The 30Mn weld, which had the highest SFE, exhibited the highest recrystallization fraction (94.8 %) and an increasing rate of hardness (40.9 %). This is because a higher SFE can enhance dislocation mobility, leading to an active rate of continuous DRX as well as discontinuous DRX. Consequently, the refinement of the recrystallized grains effectively assisted the hardening of the 30Mn weld after FSW. Hence, we concluded that SFE should be considered to improve the properties of TWIP steels after FSW.

Comparative study on mechanism of hydrogen embrittlement of Fe–18Mn-0.6C twinning-induced plasticity (TWIP) steel subjected to friction-stir welding (FSW) and tungsten inert-gas (TIG) welding

In present study, we investigated the effect of welding technique on resistance of hydrogen (H) embrittlement in Fe–18Mn-0.6C (wt.%) twinning-induced plasticity (TWIP) steel by using an electrochemical H-charging, thermal desorption spectroscope, and electron microscope. The friction-stir welding (FSW) specimen was less sensitive to H embrittlement relative to base metal and tungsten inert-gas (TIG) welding specimens by differences in microstructure and deformation mechanism. During H-charging of the FSW specimen, numerous dislocations/Σ3 boundaries reduced H diffusion into specimen interior, causing shallowest depth of brittle fracture. In contrast, the depth of brittle fracture in the H-charged TIG specimen was much larger due to rapid H diffusion by decreased grain boundaries including Σ3 annealing twin boundaries. During tensile deformation, the H-charged FSW specimen underwent the reduction in stress concentration by inactive TWIP as well as strong resistance of boundary decohesion. It was because of alleviation of H-enhanced localized plasticity (HELP) mechanism, leading to suppression of H-induced crack growth. Conversely, the H-charged base metal and TIG specimens revealed large stress concentration by active TWIP and weak boundaries owing to strong effects of HELP + H-enhanced decohesion (HEDE) mechanisms, exhibiting rapid H-induced crack propagation.

Hot Deformation Behavior and Dynamic Recrystallization Mechanism of Fe-18.2Mn-0.52C Twinning-Induced Plasticity Steel

Hot Deformation Behavior and Dynamic Recrystallization Mechanism of Fe-18.2Mn-0.52C Twinning-Induced Plasticity Steel

Superior strength and wear resistance of mechanically deformed High-Mn TWIP steel

In the present study, the mechanical and wear behaviour of the surface-mechanically treated high-manganese (high-Mn) twinning-induced plasticity (TWIP) steel were investigated. The TWIP alloy was first designed and fabricated via surface-mechanical attrition treatment (SMAT) system and the mechanical properties including strength, wear behaviour as well as the microstructural evolution were thereafter determined. Transmission electron microscopy (TEM) characterization revealed a typical dislocation as a result of the surface treatment as well as the formation of twin layers with a reduced stacking fault energy (SFE). Due to the ultra-fine grain refinement caused by plastic deformation during surface treatment, a microhardness value of 489 HV can be obtained after treatment. Likewise, the yield strength of the high-Mn TWIP steel could be enhanced from 360 MPa to 813 MPa and a reduction in elongation to failure of about 20 % can be achieved. The wear test showed that the treated TWIP steel possessed a reduced friction coefficient and improved wear resistance at different testing loads, attributed to the nanoscale refinement of grains induced during treatment. The strength, hardness, and wear resistance of the fabricated TWIP alloy improves significantly, thanks to surface treatment by SMAT.

High dislocation density TWIP steel with an excellent combination of strength and plasticity

After undergoing 75% hot deformation and 40% cold deformation, a variant of TWIP (Twin Induced Plasticity) steel with a composition of Fe–22Mn−2.7Al−0.95C−0.75Si (wt.%) was subjected to annealing at various temperatures (850 °C, 650 °C, 550 °C) for 20min. The recovery annealed C550 sample exhibited a yield strength of 1289.20 MPa, a tensile strength of 1442.29 MPa and an elongation of 30.78%. Characterization and comparison of the samples were conducted using XRD, SEM, EBSD, TEM and uniaxial tensile tests. The yield strength of the sample was assessed through different strengthening mechanisms to analysis the exceptional properties of the recovery annealed sample. Experimental findings indicate that the high-density dislocation and the refinement of slip bands in the recovery annealed C550 samples contribute to their superior performance compared to the partially and fully recrystallized samples.