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At cryogenic temperatures, 316L austenitic stainless steel (ASS) exhibits remarkable strength while retaining high ductility, defying the conventional stress-strain trade-off. Despite extensive studies documenting the cryo-tensile properties of ASSs, the underlying mechanisms behind this phenomenon remain largely unexplored. This study systematically re-examines the tensile properties of 316L stainless steel and the associated mechanisms across a range of low temperatures (293 K, 223 K, 123 K, and 77 K). The reasons for the superior stress-strain balance (∼80 % GPa) are discussed using results from electron backscatter diffraction (EBSD) microstructure characteristics. The results undoubtedly suggest that the transformation mechanisms, specifically the shift from deformation twinning to martensitic transformation (γ → ε → α′), play a crucial role in enhancing elongation at cryogenic temperatures. At these temperatures, the Gibbs free energy difference between ε-martensite and γ-austenite approaches zero, resulting in slow martensite growth. The stress-strain curves at low temperatures satisfy the Considère criterion, indicating delayed necking under these conditions. This behavior is ascribed to the presence of various hierarchical microstructures, including ε, α′, γ-twins, ε-twins and their intersections, which act as sources of work hardening. This study provides new insights into deformation behavior of ASSs under cryogenic conditions.

A novel strategy involving warm rolling and tempering-annealing was introduced to optimize the strength-ductility balance of Fe-10.2Mn-2.2Al-0.41C-0.6 V (wt. %) steel. The V- and κ-carbide particles produced during the tempering are critical for tailoring the austenite characteristics during the subsequent annealing. Austenite that nucleates on Mn-rich κ-carbides inherit their high Mn content and fine grain size. Quantitative calculations suggest that the pinning effect exerted by the V-carbide particles strongly resists grain boundary motion and recrystallization grain growth, further refining the final microstructure. Moreover, the dual nano-sized particles induce abnormal variations in the grain size and fraction of austenite, influencing the deformation mechanisms. In the absence of deformation twins, the fresh martensite develops into “separating walls” to refine the microstructure and further enhances the work hardening in addition to the complex dislocation mobile. Finally, the tempered-annealed sample demonstrated a simultaneous increase in the yield and tensile strengths from 1166 to 1452 MPa and 1507–1727 MPa, but a slight decrease in the total elongation from 18.6% to 16.8% compared to annealed sample, achieving a good strength-ductility balance.

With the addition of microalloy elements to a high-strength low-alloy (HSLA) steel, various fine particles of carbides and nitrides are formed, which increase the matrix strength. These precipitates play a crucial role in precipitation strengthening. However, the role of precipitates in microstructural refinement is frequently overlooked. In this study, a series of hot-rolled HSLA steel samples were reheated to different temperatures above the austenite transformation point for a specified period to refine austenite grains via precipitation, then cooled to a dual-phase (austenitic/ferritic) region, and finally air-cooled to room temperature. The influences of different austenitising conditions on the microstructure and mechanical properties of the HSLA steel were examined. When a hot-rolled sample was reheated to 15 °C above the austenitic transition temperature for 20 min and then cooled to 25 °C below the austenitic transition temperature for 25 min, the most low-angle boundaries were formed, and the smallest effective grain size was achieved. Meanwhile, compared with the hot-rolled sample, the tensile and yield strengths of the reheated sample increased by 12.3% and 3.4%, respectively, while the elongation increased by 162.5%, exhibiting a good strength–ductility balance. By adopting an appropriate austenitising process, precipitates can refine the crystalline grains during austenitisation, thereby enhancing the comprehensive mechanical properties of the steel. Meanwhile, excessively high austenitising temperatures lead to the coarsening of the steel microstructure, decreasing the microstructural refinement efficiency via precipitation and consequently degrading the comprehensive mechanical properties of the steel. The findings provide valuable insights into the preparation process design of such steels or other steels with similar microstructures. [ABSTRACT FROM AUTHOR]

We attempted to improve the strength–ductility balance of tempered martensite steel by controlling cementite particle size distribution. Four types of samples of varying tempering temperatures were prepared: T973-60m and T823-60m samples were heated to 973 and 823 K and isothermally held for 1 h, while DT-60m and DT-15m samples were heated to 973 K and isothermally held for 1 h and 15 min and cooled to 823 K and isothermally held for 15 min and 1 h. As a result, the strength–ductility balance of DT-60m and DT-15m samples using two-stage tempering was superior to that of T973-60m and T823-60m samples. From microstructural observations, T973-60m sample mainly included large cementite particles in contrast to T823-60m sample which mainly included small cementite particles. DT-60m and DT-15m samples included both small and large cementite particles. The larger the area fraction of the small cementite particles, the higher was the tensile strength and the larger the area fraction of the large cementite particles, the higher was the total elongation. In the case of DT-60m and DT-15m samples, the nucleated voids were hard to coalesce due to the suppression of strain concentration at the interface between the matrix and coarse cementite particles. From these results, we concluded that strength–ductility balance could be improved by dispersing both small and large cementite particles. [ABSTRACT FROM AUTHOR]

The thermal properties, microstructure, and mechanical properties of Fe-18Mn-3Ti (wt%) were investigated, focusing on the effects of different heat-treatment processes. Results revealed that the 450 °C warm-rolling sample (450 WR) exhibited promising mechanical properties. Specifically, this sample displayed a yield strength of 988 MPa, an ultimate tensile strength of 1052 MPa, and total elongation of 15.49%. Consequently, a favorable strength-ductility balance was achieved. The strain-hardening ability surpassed that of the cold rolling sample (CR). Microstructure analysis indicated the simultaneous occurrence of dynamic equilibrium between grain deformation and re-crystallization because of the co-influence of thermal and strain in the warm rolling process. This desirable mechanical property was attributed to the presence of a multi-phase (α-martensite, austenite, and ε-martensite) and heterogeneous microstructure. The improvement of ultimate tensile strength was based on grain refinement, grain co-deformation, and the transformation-induced plasticity (TRIP) effect in the early stage of plastic deformation (stage Ⅰ). The improvement of ultimate elongation (TEL) was ascribed to the TRIP effect in the middle stage of plastic deformation (stage Ⅱ). [ABSTRACT FROM AUTHOR]

A remarkable balance between the strength (844 MPa) and ductility (35.6%) of the Ti–4V–2Mo–2Fe alloy was achieved by hot rolling. Notably, alloy specimens rolled at 700 °C exhibited a yield strength exceeding 1 GPa. This outstanding yield strength from several factors: fine-grain strengthening, dislocations strengthening in the non-recrystallized region, and precipitation strengthening of α phase and isothermal ω phase. Within the 750–900 °C temperature range, a notable enhancement in yield strength, uniform elongation, total elongation, and work hardening rate was observed as rolling temperature decreased. This enhancement can be attributed to the “dynamic Hall-Petch effect” caused by the stress-induced {332} twins. Additionally, grain refinement and stress-induced ω phase further enhanced ductility and work hardening capacity. These findings show that reasonable adjustment of microstructure and deformation mechanism is an effective strategy to achieve excellent strength-ductility balance of metastable β titanium alloys.

Mechanical properties of lean Mg-xLi-1RE-0.5Zn-0.5Zr alloys after hot working by the extrusion process were systematically investigated. By increasing Li content, the coarsening of the dynamic recrystallization (DRX) grain size (D) was recorded. This was ascribed to the decrease of the solidus temperature (TSolidus) by increasing Li content, and hence, the increase of the homologous temperature during hot deformation (T/TSolidus). As a result, the tensile yield stress (TYS), ultimate tensile strength (UTS), compressive yield stress (CYS), and ultimate compressive strength (UCS) decreased by increasing Li content. Accordingly, the Hall-Petch relationships of TYS = 145.8 + 69/√D and CYS = 69.3 + 100/√D were proposed, where TYS, CYS, and D are expressed in MPa, MPa, and μm, respectively. However, total elongation in the tension test and fracture strain in the compression test were significantly improved and the crystallographic texture intensity decreased by increasing the Li content. These improvements were found to be quite beneficial for overcoming and breaking the strength–ductility trade-off. The mechanical behavior of these alloys was compared to other competitive alloys for lightweight applications.

The effects of Li content on the mechanical properties of lean Mg-1RE-0.5Zn-0.5Zr-xLi alloys in the as-cast condition were investigated, for which the improvement of mechanical properties due to the advantages of Li, RE (rare earth), Zn, and Zr addition were considered. Lithium up to 3 wt% resulted in the grain refinement of α-Mg matrix but effectively saturated thereafter. Moreover, a decrease in the crystallographic texture intensity was observed. Accordingly, the addition of 3 wt% Li improved the mechanical properties, as evaluated by the tension and compression tests. Moreover, the strength-ductility synergy improved, as investigated by the tensile toughness. However, Li concentrations higher than ~ 3 wt% led to the appearance of the deleterious intergranular α-Mg/β-Li eutectics, resulting in inferior as-cast mechanical behavior. Finally, Hall–Petch formulae of σT = 59.5 + 299.6/√D and σC = 47.5 + 294.6/√D were proposed for tensile and compressive yield stresses, respectively. Accordingly, this work revealed that the as-cast Mg-1RE-0.5Zn-0.5Zr-3Li alloy is a promising candidate for future lightweight applications. [ABSTRACT FROM AUTHOR]

We elucidate here the influence of the rolling process on the microstructure and tensile properties of Mg-1Ca-0.5Mn-0.53Ce alloy. Intriguingly, the alloy subjected to 5-pass low-temperature rolling exhibited an excellent strength-ductility balance (ultimate tensile strength (UTS) = 261.4 MPa and elongation (EL) = 20%), which was far better than the one subjected to 4-pass low-temperature rolling (UTS = 218.3 MPa and EL = 4.3%). The coarse Mg2Ca particles in the 4-pass sample led to the local stress concentration, with consequent initiation of micro-cracks at the early deformation stage. In contrast, the microstructure of the 5-pass sample characterized by homogeneous ultra-fine grain, double peak texture, and refined precipitates contributed to the superior tensile properties. [ABSTRACT FROM AUTHOR]

The development of robust alloys capable of maintaining high strength and ductility at cryogenic temperatures has been a long-sought goal, particularly for load-bearing applications in extremely low-temperature environments. In this study, we reported a newly developed face-centered-cubic (FCC) metastable (Ni0·3Co0·4Cr0.3)94Mo6 medium-entropy alloy (Mo-MEA) with an excellent synergy of strength and ductility at 77 K, surpassing the toughest equiatomic NiCoCr MEA. Compared to the equiatomic NiCoCr MEA, the Mo-MEA exhibited a substantial increase in yield strength by 68 % (from 407 to 685 MPa) and a decent enhancement of the ultimate tensile strength by 10 % (from 1289 to 1415 MPa), along with a marginal increase in elongation from 75 % to 78.45 %. Electron backscatter diffraction and transmission electron microscopy revealed the activation of multimodal deformation mechanisms, including dislocations, stacking faults, twinning, and FCC-to-hexagonal-close-packed phase transformation, during the tensile deformation at 77 K.

With the addition of microalloy elements to a high-strength low-alloy (HSLA) steel, various fine particles of carbides and nitrides are formed, which increase the matrix strength. These precipitates play a crucial role in precipitation strengthening. However, the role of precipitates in microstructural refinement is frequently overlooked. In this study, a series of hot-rolled HSLA steel samples were reheated to different temperatures above the austenite transformation point for a specified period to refine austenite grains via precipitation, then cooled to a dual-phase (austenitic/ferritic) region, and finally air-cooled to room temperature. The influences of different austenitising conditions on the microstructure and mechanical properties of the HSLA steel were examined. When a hot-rolled sample was reheated to 15 °C above the austenitic transition temperature for 20 min and then cooled to 25 °C below the austenitic transition temperature for 25 min, the most low-angle boundaries were formed, and the smallest effective grain size was achieved. Meanwhile, compared with the hot-rolled sample, the tensile and yield strengths of the reheated sample increased by 12.3% and 3.4%, respectively, while the elongation increased by 162.5%, exhibiting a good strength–ductility balance. By adopting an appropriate austenitising process, precipitates can refine the crystalline grains during austenitisation, thereby enhancing the comprehensive mechanical properties of the steel. Meanwhile, excessively high austenitising temperatures lead to the coarsening of the steel microstructure, decreasing the microstructural refinement efficiency via precipitation and consequently degrading the comprehensive mechanical properties of the steel. The findings provide valuable insights into the preparation process design of such steels or other steels with similar microstructures.

The thermal properties, microstructure, and mechanical properties of Fe-18Mn-3Ti (wt%) were investigated, focusing on the effects of different heat-treatment processes. Results revealed that the 450 °C warm-rolling sample (450 WR) exhibited promising mechanical properties. Specifically, this sample displayed a yield strength of 988 MPa, an ultimate tensile strength of 1052 MPa, and total elongation of 15.49%. Consequently, a favorable strength-ductility balance was achieved. The strain-hardening ability surpassed that of the cold rolling sample (CR). Microstructure analysis indicated the simultaneous occurrence of dynamic equilibrium between grain deformation and re-crystallization because of the co-influence of thermal and strain in the warm rolling process. This desirable mechanical property was attributed to the presence of a multi-phase (α-martensite, austenite, and ε-martensite) and heterogeneous microstructure. The improvement of ultimate tensile strength was based on grain refinement, grain co-deformation, and the transformation-induced plasticity (TRIP) effect in the early stage of plastic deformation (stage Ⅰ). The improvement of ultimate elongation (TEL) was ascribed to the TRIP effect in the middle stage of plastic deformation (stage Ⅱ).

This research focuses on the systematic study of a Ti-6Al-2Sn-4Zr-2Mo-Si titanium alloy and the characterization of α + β (equiaxed and bimodal) and α + β (duplex) microstructures. It provides more insights on the outstanding advantages of the duplex (α + α) micro structure, especially on its exceptional work hardening and strength-ductility balance. The heat treatment conditions required to form equiaxed, bimodal and duplex microstructures and their effects on the grain size and the phase proportion are discussed. It shows how the micro structural parameters can be controlled thanks to the heat treatment temperatures, the holding times and possible aging processes. The influence of such microstructural factors on the tensile properties of each alloy is investigated, especially on strength (proof stress, ultimate tensile strength), ductility (plastic elongation) and work hardening properties. The duplex (aα+ β) micro structure is compared with the equiaxed and bimodal microstructures and its advantages are displayed, highlighting the better strength-ductility balance and superior work hardening properties of the duplex microstructure. Indeed, the deformed microstructure of the duplex (α + β) microstructure reveals more homogeneous strain partitioning than that of the bimodal (α + β) microstructure. Thus, this work proved the potential of an optimized duplex (α + β) microstructure for the enhanced tensile properties at room temperature. Finally, a machine learning model using gradient boosting regression trees is used to quantify the importance of the microstructural factors (type of microstructure, grain size and phase ratio) on the mechanical properties. [ABSTRACT FROM AUTHOR]

• Strength-ductility synergy was tailored by coupling between grain refinement and the TRIP effect. • Reducing SFE minimizes the detrimental effect of grain refinement on the ductility of TRIP alloys. • Fast kinetics of deformation-induced transformation due to extremely low SFE must be avoided. • Fe 47 Co 30 Cr 10 Ni 5 V 2 Si 6 HEA showed exceptional elongation (∼65 %) at ultrahigh UTS of 1250 MPa. • SFE should be in a desirable range to tune the kinetics of martensitic phase transformation. In-depth knowledge of the coupling between grain refinement and the transformation-induced plasticity (TRIP) effect in metastable alloys is a viable approach for the improvement of strength-ductility synergy, which needs systematic research with consideration of commercial austenitic stainless steels and novel high-entropy alloys (HEAs). Accordingly, in the present work, two Si-containing metastable HEAs in the Fe 47 Co 30 Cr 10 Ni 5 V 8- x Si x system (x = 3 and 6 at.%) were designed, and the TRIP-assisted AISI 304L stainless steel was also considered for comparison. The alloys were processed by cold rolling and annealing to obtain different grain sizes. Reducing the stacking fault energy (SFE) through adjusting chemical composition contributes to minimizing the detrimental effect of grain refinement on the ductility of TRIP alloys, while extremely low SFE must be avoided owing to the fast kinetics of deformation-induced martensitic phase transformation, which leads to the deterioration of ductility. In contrast to AISI 304L stainless steel, a strong TRIP effect was maintained upon grain refinement in the Fe 47 Co 30 Cr 10 Ni 5 V 2 Si 6 HEA due to the remaining apparent SFE in the appropriate TRIP range. The tuned kinetics of martensitic transformation was found to be responsible for the exceptional ductility (∼65 %) of Fe 47 Co 30 Cr 10 Ni 5 V 2 Si 6 HEA at an ultrahigh tensile strength of ∼1230 MPa. Therefore, considering the identical trend of SFE with grain size, an appropriate initial SFE value is important for tuning the grain size dependency of the TRIP effect. Moreover, the ultrahigh strength was attributed to the high volume fraction of α΄-martensite as well as the high strength of the martensite phase due to the high Si content. Accordingly, for achieving strong-yet-ductile HEAs, a high Si content is recommended to benefit from solid solution strengthening in the martensite phase, a specially-designed chemical composition is needed for attaining a high volume fraction of α΄-martensite, and SFE should be in a desirable range to tune the kinetics of martensitic phase transformation. [Display omitted] [ABSTRACT FROM AUTHOR]

FeNiV alloys exhibit potential applications in magnetic, radiation-resistant, mechanical, and superconducting fields, however, the formation of the hard yet brittle sigma phase enriched with Fe and V hindered their application in extreme environments. Therefore, improving the mechanical properties of FeNiV alloys has been a crucial problem. In this study, a series of as-cast FeNiVAl x (values of x is 0, 0.1, 0.2, 0.3) medium-entropy alloys (MEAs) were fabricated by vacuum arc melting, and the evolution of microstructure and mechanical properties with different Al microalloying were investigated systematically. As the Al content increased, FeNiVAl x MEAs underwent a structural transformation from a dual-phase structure consisting of a FCC phase (46.4 %; phase content) and a sigma phase (53.6 %) at x=0 to a single BCC phase in FeNiVAl 0.3 , while the mechanical properties of the alloy show a decrease in strength and a significant increase in elongation. Notably, the FeNiV alloy exhibits the highest yield strength of 1851 MPa with 7.8 % ductility. In contrast, the FeNiVAl 0.2 alloy demonstrated superior comprehensive compressive properties, with a high yield strength of 1255 MPa and an exceptional ductility exceeding 50 % without fracturing. The elimination of the harmful sigma phase, coupled with the formation of BCC phase, contributes to the observed decrement in strength and increment in ductility. This study elucidates the intrinsic relationship between microstructure and mechanical properties with Al contents in FeNiVAl x alloys, providing insights for the design of MEAs with excellent strength-ductility balance through microalloying. • Microstructure evolution and mechanical properties of FeNiVAl x MEAs were investigated systematically. • As the Al content increased, the hard yet brittle sigma phase was eliminated, and the BCC phase was formed. • The FeNiVAl 0.2 and FeNiVAl 0.3 alloys demonstrated superior comprehensive compressive properties. • The deformation mechanisms of FeNiVAl x MEAs were revealed. [ABSTRACT FROM AUTHOR]

In this work, new TZM alloys containing 0.5 wt% and 1.0 wt% ZrO 2 were prepared by powder metallurgy method, and their annealed microstructures and mechanical properties were studied. The TZM alloy sheet with 94 % deformation was recrystallized at 1200°C, and the elongation was greatly increased, and its UTS, YS and EL were 573 ± 10 MPa, 431 ± 7 MPa and 44 ± 0.2 %, respectively. After adding 0.5 wt% c-ZrO 2 , the best strength-ductility balance was achieved, and its UTS, YS, EL and PSE are 621 ± 3 MPa, 527 ± 4 MPa, 41.3 ± 0.58 % and 25.6 GPa·%, respectively, which was much larger than the PSE combinations of most Mo and TZM alloys. Microstructure analysis shows that the excellent synergistic effect arises from the low O impurity content and the control of dislocation density and dislocation slip by c-ZrO 2 and the annealing process. Within the alloy, Ti and Zr react with O to produce TiO 2 and ZrTiO 4 , which reduces the content of O impurities. Annealing provides sufficient space for dislocation slip, which coordinates the rotation of grain orientation during the stretching process. Coupled with the low O impurity concentration, results in excellent ductility of TZM alloys. Additionally, c-ZrO 2 can effectively fix dislocations within the grains and interact strongly with dislocations, consequently enhancing the strength of the TZM alloy. [Display omitted] • Extraordinary strength-ductility balance (25.6 GPa·%) is achieved in TZM sheet. • It is innovatively found that c-ZrO 2 can adsorb ZrTiO 4 layer. • Low O impurity content and recrystallization significantly increase the elongation. • The interaction between c-ZrO 2 and intragranular dislocations increases the strength. [ABSTRACT FROM AUTHOR]

Lightweight refractory high-entropy alloys (LRHEAs) have received significant attention due to their excellent strength-plasticity matching. Generally, its strengthening mechanism mainly comes from solid solution strengthening caused by atomic radius mismatches, but excessive atomic radius mismatch can reduce the phase stability of solid solution and easily generate precipitated phases to reduce the plasticity. Here, we present a strategy to enhance the shear modulus mismatch while improving the mechanical properties and phase stability of LRHEAs. We chose the TiZrVNbAl system as the LRHEAs model. The addition of Mo resulted in a modulus mismatch induced strength contribution of 564 MPa, which accounts for ∼57 % of the total strength. Compared to the alloy without Mo, the strength increased by ∼42 % without any loss of ductility. More importantly, the addition of Mo significantly reduces the diffusion coefficient of the main element and realizes the effective kinetic suppression of the precipitated phase. This enables the alloy to avoid brittle precipitate generation even after aging at 500 °C for 5 h, and hence the excellent mechanical properties are well kept. Additionally, the strength of the LRHEA is increased by more than two times at 700 °C, demonstrating higher high temperature performance compared to RHEAs with tensile ductility. Utilizing the shear modulus mismatch strategy can effectively enhance the solid solution strengthening effect, improving the comprehensive mechanical properties of the alloy at room temperature and high temperature, while also improving phase stability. This provides a new approach to developing structurally stable high-performance alloys. • Mo addition increases the strength by ∼42 % and maintains excellent ductility. • The addition of Mo significantly enhances the phase stability of LRHEAs. • The diffusion coefficient is significantly reduced by the addition of Mo. [ABSTRACT FROM AUTHOR]

[Display omitted] This study investigates the potential of generative adversarial networks (GANs) and finite element method (FEM) for assessing the tensile properties of dual-phase (DP) steels, which are essential for lightweight and crash-resistant automotive applications. DP steels are renowned for their high strength and ductility, and their microstructure plays a crucial role in determining these tensile properties. GANs are a promising approach to learning and extracting the complex morphological features of real microstructure and precisely generating realistic images with diversity. This study employs GANs to produce synthetic microstructural images of DP steels, allowing the rapid generation of a diverse dataset. These GAN-generated microstructural images accurately reflect the metallurgical and morphological features of real DP steels. FEM simulations are then utilized to determine the corresponding tensile properties. The simulation results reveal that the martensite fraction is highly correlated with tensile strength, and uniform elongation depends on the microstructural morphology as well as the martensite fraction. Generally, GAN-generated microstructures exhibit properties similar to those of real microstructures, with some generated microstructures surpassing their real counterparts in strength–ductility products. This study emphasizes the critical role of microstructural morphology in determining tensile properties and demonstrates the potential of GANs and FEM for the efficient evaluation of the properties of DP steel and optimization of microstructures to improve performance. These insights offer valuable contributions to materials research in the automotive industry. [ABSTRACT FROM AUTHOR]

A laminated structured 2205 duplex stainless steel (DSS) with graded grain size was prepared via aluminothermic reaction and subsequent hot rolling with deformation of 80% at 1000°C, and its mechanical properties, strengthening and toughening mechanism were studied. Our materials have extraordinary elongation of 54% and high tensile strength of 990 MPa. The lamellar structure is characterized with heterogeneous lamella austenite (with nano-grain, ultrafine grain, micro-grain and nano-twin) and ferrite (with ultrafine grain and a proper amount of micro grain) coalesced alternately. The high strength is attributed to strengthening of complex grain (distribution from nanoscale to microscale) and interfaces arising from hierarchical and laminated dual-phase heterogeneous structure and distribution. The unusual high ductility is thought to be mainly attributed to the lamellar structure and dislocation hardening. [ABSTRACT FROM AUTHOR]

Ferritic–martensitic dual-phase (DP) steels are prominent and advanced high-strength steels (AHSS) broadly employed in automotive industries. Hence, extensive study is conducted regarding the relationship between the microstructure and mechanical properties of DP steels due to the high importance of DP steels in these industries. In this respect, this paper was aimed at reviewing the microstructural characteristics and strengthening mechanisms of DP steels. This review article represents that the main microstructural characteristics of DP steels include the ferrite grain size (FGS), martensite volume fraction (MVF), and martensite morphology (MM), which play a key role in the strengthening mechanisms and mechanical properties. In other words, these can act as strengthening factors, which were separately considered in this paper. Thus, the properties of DP steels are intensely governed by focusing on these characteristics (i.e., FGS, MVF, and MM). This review article addressed the improvement techniques of strengthening mechanisms and the effects of hardening factors on mechanical properties. The relevant techniques were also made up of several processing routes, e.g., thermal cycling, cold rolling, hot rolling, etc., that could make a great strength–ductility balance. Lastly, this review paper could provide substantial assistance to researchers and automotive engineers for DP steel manufacturing with excellent properties. Hence, researchers and automotive engineers are also able to design automobiles using DP steels that possess the lowest fuel consumption and prevent accidents that result from premature mechanical failures.

The work prepared Al 0·4 CoCu 0·6 Ni(Si 0.2 )Ti x (Si 0 Ti x (x ≤ 1.0) and Si 0.2 Ti x (x ≤ 0.5)) high entropy alloys (HEAs) with high strength and excellent plasticity by optimizing the added ratio of Ti and rapid cooling, discussed the effects of Ti and cooling rate on HEAs' microstructures and mechanical properties. The results showed that arc melted and copper injected Si 0 Ti x HEAs' phase structures changed gradually from “fcc + L1 2 (Si 0 Ti 0.25 )” to “fcc + L1 2 +minor bcc (Si 0 Ti 0.5 )” and finally to “fcc + L1 2 +bcc + Ni 3 Ti-type phase (Si 0 Ti 0.75 , Si 0 Ti 1.0 )”. But they transformed from “fcc + L1 2 +bcc + Ni 16 Ti 6 Si 7 -type phase (Si 0·2 Ti 0.25 )” to “fcc + L1 2 +bcc + AlNi 2 Ti-type + Ni 16 Ti 6 Si 7 -type phase (Si 0·2 Ti 0.5 )” for Si 0.2 Ti x HEAs. The micro-hardness of arc melted and copper injected HEAs gradually increased compared with Si 0 Ti 0 matrix HEA and that of copper injected HEAs were larger than arc melted HEAs (except Si 0 Ti 0.5 ). The compressive properties of Si 0 Ti 0.25 , Si 0 Ti 0.5 and Si 0·2 Ti 0.25 HEAs were relatively better, in which, the yield strengths of copper injected Si 0 Ti 0.25 , Si 0 Ti 0.5 and Si 0·2 Ti 0.25 HEAs were 2.7, 2.9 and 4.8 times than that of arc melted Si 0 Ti 0 matrix HEA (295 MPa), the fracture strain rates of the corresponding HEAs were 47.1%, 22.4% and 13.5% respectively. It introduced three strengthening mechanisms of solid solution strengthening, trace phase transformation and fine grain strengthening and realized HEAs' strength-ductility balance. [ABSTRACT FROM AUTHOR]

Data-driven models have been constructed for Dual Phase (DP) and Interstitials Free (IF) steels using an evolutionary approach. DP steel data are utilized from an existing database, while for the IF steels, data generated at an integrated steel plant have been used. The objective function for Ultimate Tensile Strength (UTS) and % elongation, created as data-driven models, is simultaneously optimized for an optimum strength-ductility balance and the results indicate the possibilities of developing steels with better mechanical properties than what are known to have been existing so far. [ABSTRACT FROM AUTHOR]

The distribution state of reinforcement in matrix plays a significant role in affecting the strength-ductility relationship in metal matrix composites. Restricted by the great distinction in geometrical size, intrinsic properties and the poor wettability, the discontinuous reinforcement particulates are commonly accustomed to being distributed at grain boundaries and thus being stuck in the disadvanced stress concentration near the interface. Herein, we report a strategy to realize the special in-situ intragranular AlN nanoparticles together with a well-bonded intergranular two-dimensional transition nanosheets/metal interface structure in boron nitride nanosheets (BNNSs)/Al system through the integrated segmented ball milling (SBM) and reaction sintering route. It is revealed that the BNNSs-AlN-Al transition interface can effectively alleviate the stress partitioning at the interface in the initial stage of plastic deformation. And the coherent intragranular AlN/Al interface benefits to a strong interfacial bonding and leading to the multiplication of intragranular dislocations during the subsequent deformation. The combined effect improved the deformation uniformity of the composites and delayed the crack propagation. As a result, a high strength-ductility balance was achieved in BNNSs/Al composites. The present work may provide a new protocol for achieving high strength-ductility synergy for metal matrix composites. [Display omitted] [ABSTRACT FROM AUTHOR]

• An unprecedented strength-ductility balance for Mo alloy is obtained by adding rare earth Y/Ce by liquid-liquid doping. • Strength-elongation product of the new Mo alloy reaches 2.4 times that of pure Mo. • The fine rare earth oxides introduce Orowan strengthening and fine grain strengthening of Mo-alloy, changing fracture mode. [Display omitted] Rare earth (Y/Ce) were homogeneously distributed in molybdenum alloys by liquid-liquid doping and powder metallurgy method, and the molybdenum alloys plates were obtained after rolling. The results show the rare earth form nanoscale Y 2 O 3 and CeO 2 particles which were concomitant in molybdenum matrix. The rare earth oxides particles significantly refine microstructure and improve mechanical properties of the rolled molybdenum plate. The adding of 0.8%Y 2 O 3 and 0.12%CeO 2 made the micro fringe spacing in microstructure of rolled molybdenum alloy reduce 52.43%. The newly developed molybdenum alloys have an unprecedented strength-ductility balance compared with previous other molybdenum alloys. And high tensile strength and elongation were obtained simultaneously. The tensile strength of the rolled Mo-0.8%Y 2 O 3 -0.12%CeO 2 alloy plate reaches 917 MPa with a 13.9% elongation, increased by 21.9% and 55.5% over a pure molybdenum plate, respectively. The strength-elongation product of the new molybdenum alloy annealed at 1200 ℃ could reach 2.4 times that of pure molybdenum. The addition of the nanoscale rare earth oxides to the Mo-alloy introduces Orowan strengthening and fine grain strengthening which changes fracture mode, resulting in excellent strength-ductility balance. [ABSTRACT FROM AUTHOR]

Tensile tests of five commercial Fe–Cr–Ni-based austenitic alloys were conducted after thermal hydrogen precharging in a pressurized gaseous environment. The divergence in Cr and Ni concentrations affected the hydrogen solubility significantly as well as the impacts of dissolved hydrogen on the mechanical performance of the alloy. Hydrogen solubility increased with increasing Cr content and Cr/Ni compositional ratio, bringing about an escalating solid-solution hardening with a magnitude of ≈ G /1000 (G : shear modulus) per atomic percent of solute hydrogen. Furthermore, hydrogen facilitated deformation twinning in alloys with relatively low stacking fault energy (lower Ni content), in which deformation twinning occurred even in a nonhydrogenated state. Augmenting the twin density enhanced the work-hardening capability at the later deformation stage, giving rise to the improvement of uniform elongation via retarded onset of plastic instability. Consolidating the experimental results and hitherto-understood hypothesis on the response to hydrogen of other austenitic materials, the essential conditions for promoting hydrogen-related strengthening and ductilization were deduced. [ABSTRACT FROM AUTHOR]

Ferritic–martensitic dual-phase (DP) steels are prominent and advanced high-strength steels (AHSS) broadly employed in automotive industries. Hence, extensive study is conducted regarding the relationship between the microstructure and mechanical properties of DP steels due to the high importance of DP steels in these industries. In this respect, this paper was aimed at reviewing the microstructural characteristics and strengthening mechanisms of DP steels. This review article represents that the main microstructural characteristics of DP steels include the ferrite grain size (FGS), martensite volume fraction (MVF), and martensite morphology (MM), which play a key role in the strengthening mechanisms and mechanical properties. In other words, these can act as strengthening factors, which were separately considered in this paper. Thus, the properties of DP steels are intensely governed by focusing on these characteristics (i.e., FGS, MVF, and MM). This review article addressed the improvement techniques of strengthening mechanisms and the effects of hardening factors on mechanical properties. The relevant techniques were also made up of several processing routes, e.g., thermal cycling, cold rolling, hot rolling, etc., that could make a great strength–ductility balance. Lastly, this review paper could provide substantial assistance to researchers and automotive engineers for DP steel manufacturing with excellent properties. Hence, researchers and automotive engineers are also able to design automobiles using DP steels that possess the lowest fuel consumption and prevent accidents that result from premature mechanical failures. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, for automotive applications, the need for new advanced high-strength sheet steels (AHSSs) with high ductility has rapidly increased. This is mainly related to the need for more fuel-efficient (and therefore more environmentally friendly) cars, and the increasing consumer demand for safer vehicles. In this research, the transformation-induced plasticity (TRIP) that accompanies the mechanically induced martensitic transformation (MIMT) in TRIP-aided multiphase steel was analyzed. The analysis was performed using a computational model that takes the ductile fracture during tensile deformation into account. The TRIP and MIMT phenomena were calculated using the concept of variant selection, which is based on the Kurdjumov–Sachs (K–S) orientation relationship. To consider the localization of the plastic flow in the deforming material, the increase in void nucleation due to the martensitic transformation and the void growth based on the yield criterion for porous material were studied. The feasibility of the extra advanced high-strength sheet steel (X-AHSS) was assessed by analyzing the results obtained using various initial volume fractions and various stabilities of the retained austenite in the TRIP-aided multiphase steel. Subsequently, the optimum volume fraction and stability of the retained austenite in the TRIP-aided multiphase steel could be determined. [Copyright &y& Elsevier]

A genetic algorithm-based analysis for the primary microstructural requirements of optimal transformation induced plasticity (TRIP) behavior of the multiphase steel is attempted. Design of primary multiphase microstructure of steel for maximum TRIP effect is perhaps the most important job in TRIP-aided steel design. The quantitative and qualitative control over the complex composite behavior of the different constituent phases present in these steels such as polygonal ferrite, bainitic ferrite, and martensite-austenite constituent is still a challenging task. In this work, the tensile behavior of the steel has been simulated using pertinent models proposed earlier. Necessary assumptions are made using domain knowledge to generalize the tensile model for the considered realm of the problem. Based upon the conflicting nature of the tensile strength and ductility of the steel, the problem is considered here as multiobjective optimization problem. The optimization constraints are inherently taken care by the typical formulation of the problem. The Pareto front results are found quite convincing for TRIP-aided steel design. [ABSTRACT FROM AUTHOR]

The first in vivo investigation of Zn-based biodegradable metal aiming to treat osteoporotic bone fractures, a soaring threat to human health, is reported in this paper. Among the newly developed biodegradable metal system (ZnLiSr), Zn0.8Li0.1Sr exhibits excellent comprehensive mechanical properties, with an ultimate tensile strength (524.33 ± 18.01 MPa) comparable to pure Ti (the gold standard for orthopaedic implants), and a strength-ductility balance over 10 GPa%. The in vitro degradation tests using simulated body fluid (SBF) shows that Zn0.8Li0.1Sr manifests a uniform degradation morphology and smaller corrosion pits, with a degradation rate of 10.13 ± 1.52 μm year−1. Real-time PCR and western blotting illustrated that Zn0.8Li0.1Sr successfully stimulated the expression of critical osteogenesis-related genes (ALP, COL-1, OCN and Runx-2) and proteins. Twenty-four weeks' in vivo implantations within ovariectomized (OVX) rats were conducted to evaluate the osteoporotic-bone-fracture-treating effects of Zn0.8Li0.1Sr, with pure Ti as control group. Micro-CT, histological and immunohistochemical evaluations all revealed that Zn0.8Li0.1Sr possesses a similar biosafety level to, while significantly superior osteogenesis-inducing and osteoporotic-bone-fracture-treating effects than pure Ti. ZnLiSr biodegradable alloys manifest excellent comprehensive mechanical properties, good biosafety and osteoporotic-bone-fracture-treating effects, which would provide preferable choices for future medical applications, especially in load-bearing positions. [ABSTRACT FROM AUTHOR]

• The mechanism of grain refinement is deformation-induced grain subdivision after rolling. • Fine grains exhibit a unique texture distribution after rolling. • Finer grains and weakened double basal texture are fabricated by annealing. • The sheet exhibits high strength-ductility balance after rolling and annealing. In present work, the high strength-ductility balance of Mg-1.03Ca-0.47Mn Mg alloy sheet was successfully fabricated by rolling and annealing. After rolling, though the yield strength (YS) and ultimate tensile strength (UTS) of sheet were improved to 235 MPa and 253 MPa, the appearance of deformation-induced grain subdivision mechanism, shear bands and {10–12} extension twins also introduced strong (0001) basal texture with basal pole inclining to rolling direction which led the elongation (EL) decreased to 3.8%. As-annealed sheet occurred static recrystallization which led to the formation of finer grain structure than as-rolled sheet, and the strong (0001) basal texture of as-rolled sheet was transformed into weak (0001) peak texture with basal pole spreading widely along TD. Therefore, as-annealed sheet exhibits high strength-ductility balance with the YS of 235 MPa, UTS of 297 MPa and EL of 16.4%. [ABSTRACT FROM AUTHOR]