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Amorphous solids are known to fail catastrophically via fracture, and cavitation at nano-metric scales is known to play a significant role in such a failure process. Micro-alloying via inclusions is often used as a means to increase the fracture toughness of amorphous solids. Modeling such inclusions as randomly pinned particles that only move affinely and do not participate in plastic relaxations, we study how the pinning influences the process of cavitation-driven fracture in an amorphous solid. Using extensive numerical simulations and probing in the athermal quasistatic limit, we show that just by pinning a very small fraction of particles, the tensile strength is increased, and also the cavitation is delayed. Furthermore, the cavitation that is expected to be spatially heterogeneous becomes spatially homogeneous by forming a large number of small cavities instead of a dominant cavity. The observed behavior is rationalized in terms of screening of plastic activity via the pinning centers, characterized by a screening length extracted from the plastic-eigenmodes. [ABSTRACT FROM AUTHOR]

The high creep strength and high radiation resistance of nanostructured ferritic alloys (NFAs) have been generally attributed to the high-density precipitation of (O, Y)-core nano-clusters and nano-oxides. In this work, the early-stage nucleation of (O, X)-core (X = La, Ce, and Hf) nano-clusters (NCs) with respect to (O, Y)-core NCs in multi-element micro-alloyed NFAs was investigated using first-principles calculations. Their competitive precipitation preference and possible growth sequence were predicted. The (O–O) pair was suggested as the most fundamental core of all types of NCs. Yttrium always has the strongest affinity with the (O–O) pairs to initiate the nucleation of NCs during the early-stage nucleation. Under the absence or depletion of yttrium, other types of (O, X)-core (X = La, Ce, Hf) structures could form, leading to different nucleation paths with the preference ordering of (O, La)-core > (O, Ce)-core > (O, Hf)-core. NC nucleation and composition in NFAs would, thus, strongly depend on the number availabilities of micro-alloying solute species in the neighborhood of the (O–O) pairs. [ABSTRACT FROM AUTHOR]

Quaternary Y–Ti–Zr–O nano-oxides form in preference to other ternary nano-oxides in Y+Ti+Zr micro-alloyed FeCr- oxide-dispersion-strengthened (ODS) ferric alloys. In this study, bulk substitution and interfacial segregation were calculated from the first-principles to explore the formation and stability of core-shelled Y–Ti–Zr–O nano-oxides. Our results were validated with previous electron microscopic characterizations. The major findings that were obtained are as follows. Quaternary Y–Ti–Zr–O nano-oxides are most likely formed as a consequence of Zr substitution of Ti in Y–Ti–O nano-oxides. Ti segregation from the matrix interior to the Y2Ti2O7 interface is a self-limiting process, and the resulting Ti-shell at Y2Ti2O7 nano-cores can hardly be thermally stable. In contrast, the Y2(Ti,Zr)2O7 nano-core due to Zr substitution can strongly trap the Zr-substituted Ti at its interface. The resulting Ti-shell can be more stable at high Zr-content Y2(Ti,Zr)2O7 nano-cores but will reduce the interface adhesion strength. The gained insights help to clarify the experimental observations and achieve a better understanding of micro-alloying effects and mechanisms in FeCr-ODS ferric alloys. [ABSTRACT FROM AUTHOR]

Here, 0.3 wt.%Zr was introduced in an Al-4 wt.%Cu-0.5 wt.%Mn-0.1 wt.%Fe alloy to investigate its influence on the microstructure and mechanical properties of the alloy. The microstructures of both as-cast and T6-treated Al–Cu–Mn–Fe (ACMF) and Al–Cu–Mn–Fe–Zr (ACMFZ) alloys were analyzed. The intermetallic compounds formed through the casting procedure include Al2Cu and Al7Cu2Fe, and the Al2Cu phase dissolves into the matrix and re-precipitates as θ′ phase during the T6 process. The introduction of Zr results in the precipitation of L12-Al3Zr nanometric precipitates after T6, while the θ′ precipitates in ACMFZ alloy are much finer than those in ACMF alloy. The L12-Al3Zr precipitates were found coherently located with θ′, which was assumed beneficial for stabilizing the θ′ precipitates during the high-temperature tensile process. The tensile properties of ACMF and ACMFZ alloys at room temperature and elevated temperatures (200, 300, and 400 °C) were tested. Especially, the yield strength of ACMFZ alloys can reach 128 MPa and 65 MPa at 300 °C and 400 °C, respectively, which are 31% and 33% higher than those of ACMF alloys. The strengthening mechanisms of grain size, L12-Al3Zr, and θ′ precipitates on the tensile properties were discussed. This work may be referred to for designing Al–Cu alloys for application in high-temperature fields. [ABSTRACT FROM AUTHOR]

This study fabricated four kinds of CoCrMnFeNiX0.1 (X = Al, Cu, Mo, Ti) high-entropy alloys through rolling with subsequent thermal treatment, to investigate the alloying effects on the microstructural evolution, mechanical properties, and electrochemical corrosion performance. High-density parallel twinning bands were observed in the as-rolled CoCrMnFeNiX0.1 alloys, excluding the Cu0.1 variant, signifying that plastic deformation was dominated by twinning. However, detwinning and thickening of twin layers was observed after annealing. This effect was more pronounced in the rolling direction-normal direction (RD-ND) plane due to the stress state induced by rolling. The introduction of Cu altered the deformation mechanism to a combination of twinning and slipping, resulting in fewer twinning bands. Notably, annealing induced the formation of abundant bamboo-shaped twinning bands (width: ~ 10 nm) in the Cu0.1 alloy, which were correlated with nano precipitated particles. Additionally, the incorporation of Mo or Al elements activated more twinning directions, thereby enhancing plasticity. For the Ti0.1 alloy, the primary factors influencing the altered tensile and electrochemical performances were the formation and growth of few precipitated particles during annealing. Consequently, the strengthening effect can be ranked in the order of Mo > Ti > Al > Cu. Therefore, the addition of Al and Ti is recommended for improving the anticorrosive property and thermal stability of recrystallized grains. [ABSTRACT FROM AUTHOR]

Medium-entropy alloys (MEAs) have recently emerged as potential replacements for traditional alloys in high-performance applications. Among the various MEAs developed, equi-atomic CoCrNi MEA stands out for its excellent mechanical performance. Nevertheless, the yield strength of this MEA having a single-phase FCC structure is not exceptionally high. This study suggests a novel approach to strengthen the MEA by adding a small quantity of Zirconium (0.2 at.%). A (CoCrNi)99.8Zr0.2 MEA was cast and homogenized, alongside a CoCrNi MEA for comparison purposes. The alloys underwent high-pressure torsion followed by annealing in a temperature range of 700–1100 °C. In the Zr-doped MEA, annealing resulted in the recrystallization within the FCC matrix, accompanied by the precipitation of finely dispersed particles (Ni7Zr2). The concurrent precipitation hindered the grain growth, maintaining refined grain sizes (0.17 – 4 µm) over a wide range of temperatures. In contrast, the grain size in the Zr-free counterpart increased rapidly above 10 µm at elevated temperatures. The Zr doping substantially increased the yield strength with a minor negative impact on the ductility. The strength enhancement was due to grain refinement, precipitation, and dislocation locking caused by the Zr segregation at dislocation sites. These phenomena and their impacts on the Hall–Petch relationship were investigated and discussed. This study proves micro-alloying as a promising strategy for strengthening MEAs, making these alloys superior to their traditional counterparts. [ABSTRACT FROM AUTHOR]

Microalloying is an effective method to improve the mechanical properties of 6063 Al–Mg–Si alloy. Here, in this work, the effects of trace Cu (0.14 wt.%) and Cr (0.10 wt.%.) additions on the microstructure and mechanical properties of 6063 Al–Mg–Si alloy were studied. The results show that the additions of two elements can cause significant age-hardening effects, and the yield and tensile strengths of the alloys are significantly increased after T6 heat treatment. Further, it is found that the Cu and Cr additions show different strengthening mechanisms in the alloy. Cu addition leads to a finer and denser distribution of the main strengthening phases in the peak aging of the alloy, as well as a large number density of the precipitated phases, resulting in an increase in the dislocation density of the alloy during strain and hindering the dislocation movement. However, Cr addition acts as an inhibitor of grain growth and results in grain refinement, which also increases the hindrance of dislocation movement during the plastic deformation of the alloy, resulting in an increase in the dislocation density, thereby strengthening the alloy. [ABSTRACT FROM AUTHOR]

In this work, we fabricated a series of severely distorted high-entropy Elinvar alloys through micro-alloying of (CoNi)50−x(TiZrHf)50Fex (in atomic percentage). Through carefully designed experiments, we demonstrate a tunable Elinvar effect that is positively correlated with overall lattice distortion in single-phase B2 high entropy alloys. Finally, we propose a simple physical model that captures the general trend of our experimental findings. [ABSTRACT FROM AUTHOR]

Controlling the electrochemical properties of non-metallic inclusions is of substantial interest in the design of corrosion-resistant alloys. To the best of our knowledge, the dissolution and pitting corrosion behavior of selenide inclusions in stainless steels and the improvement of the pitting corrosion resistance of type 304 stainless steels via Se microalloying have not been investigated. In this study, stainless steel specimens containing artificial MnS and MnSe inclusions were fabricated via spark plasma sintering to systematically investigate their electrochemical properties. The superior pitting corrosion resistance and dissolution resistance of MnSe to those of MnS were demonstrated. The results obtained from the sintered specimens were applied to improve the pitting corrosion resistance of type 304 stainless steels via Se microalloying. Adding a trace amount of Se (0.005 mass%) altered the readily soluble sulfide inclusions to dissolution-resistant selenide-type inclusions, resulting in improved pitting corrosion resistance of type 304 stainless steel. [ABSTRACT FROM AUTHOR]

High-carbon hardline steels are primarily used for the manufacture of tire beads for both automobiles and aircraft, and vanadium (V) microalloying is an important means of adjusting the microstructure of high-carbon hardline steels. Using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM), the microstructure and precipitation phases of continuous cooled high-carbon steels were characterized, and the vanadium content, carbon diffusion coefficient, and critical precipitation temperature were calculated. The results showed that as the V content increased to 0.06 wt.%, the interlamellar spacing (ILS) of the pearlite in the experimental steel decreased to 0.110 μm, and the carbon diffusion coefficient in the experimental steel decreased to 0.98 × 10−3 cm2·s−1. The pearlite content in the experimental steel with 0.02 wt.% V reached its maximum at a cooling rate of 5 °C·s−1, and a small amount of bainite was observed in the experimental steel at a cooling rate of 10 °C·s−1. The precipitated phase was VC with a diameter of ~24.73 nm, and the misfit between ferrite and VC was 5.02%, forming a semi-coherent interface between the two. Atoms gradually adjust their positions to allow the growth of VC along the ferrite direction. As the V content increased to 0.06 wt.%, the precipitation-temperature-time curve (PTT) shifted to the left, and the critical nucleation temperature for homogeneous nucleation, grain boundary nucleation, and dislocation line nucleation increased from 570.6, 676.9, and 692.4 °C to 634.6, 748.5, and 755.5 °C, respectively. [ABSTRACT FROM AUTHOR]

Al-based foams have drawn increasing attention from industry due to their integration of structure and functional properties. However, large-sized Al-based foams still cannot be homogeneously strengthened by long-time aging due to their low thermal conductivity. In this study, we proposed an age-hardening approach that was applied in large-sized Al-0.16Sc-0.17Zr (wt.%) foams via micro-alloying with Zr and Ti compared with Al-0.21Sc foams; it not only achieved homogeneous strength by long-term aging but also reduced the cost of the alloy by substituting Zr and Ti for the more expensive Sc content. The results show that the Al3(Sc, Zr, Ti) phase with a core–shell structure as a crucial precipitation strengthening phase by micro-alloying with Zr and Ti was less prone to coarsening after a prolonged aging heat treatment. Therefore, the yielding strength of Al-Sc foam micro-alloying with Zr and Ti remained almost unchanged after a maximum aging time of 1440 h due to less coarsening precipitate, which is consistent with the results of mechanical experiments. These findings provide a new way for the heat treatment strengthening of large-sized Al-based foams, thus promoting their industrial applications. [ABSTRACT FROM AUTHOR]

This study focuses on exploring the effects of niobium (Nb)-microalloying on the properties of steel for ultra-high-strength bridge cables during hot-rolling processes. We employed a combination of dual-pass compression tests, stress–strain curve analysis, and Electron Backscatter Diffraction (EBSD) techniques to investigate the influence of Nb-microalloying on the static recrystallization behavior and grain size of the steel. The key findings reveal that Nb-microalloying effectively inhibits static recrystallization, particularly at higher temperatures, significantly reducing the volume fraction of recrystallized grains, resulting in a finer grain size and enhanced deformation resistance. Secondly, at a deformation temperature of 975 °C, Nb-containing steel exhibited finer grain sizes compared to Nb-free steel when held for 10 to 50 s; however, the grain size growth accelerated when the hold time exceeded 50 s, likely linked to the increased deformation resistance induced by Nb. Lastly, this research proposes optimal hot-rolling process parameters for new bridge cable steel, recommending specific finishing rolling temperatures and inter-pass times for both Nb-containing and Nb-free steels during the roughing and finishing stages. This study suggests optimal hot-rolling parameters for both Nb-containing and Nb-free steels, providing essential insights for improving hot-rolling and microalloying processes in high-carbon steels for bridge cables. [ABSTRACT FROM AUTHOR]

PbSn solders are used in semiconductor devices for aerospace or military purposes with high levels of reliability requirements. Microalloying has been widely adopted to improve the reliability for Pb-free solders, but its application in PbSn solders is scarce. In this article, the optimization of PbSn solder reliability with Ge microalloying was investigated using both experimental and calculation methods. Intermetallic compounds (IMC) growth and morphologies evolution during reliability tests were considered to be the main factors of device failure. Through first-principle calculation, the growth mechanism of interfacial Ni3Sn4 was discussed, including the formation of vacancies, the Ni-vacancies exchange diffusion and the dominant Ni diffusion along the [1 0 0] direction. The doping of Ge in the cell increased the exchange energy barrier and thus inhibited the IMC development and coarsening trend. In three reliability tests, only 0.013 wt% Ge microalloying in Pb60Sn40 was able to reduce IMC thickness by an increment of 22.6~38.7%. The proposed Ge microalloying method in traditional PbSn solder could yield a prospective candidate for highly reliable applications. [ABSTRACT FROM AUTHOR]

Thin twin-roll cast strips from a model Al-Cu-Mg-Li-Zr alloy with a small addition of Sc were prepared. A combination of a fast solidification rate and a favorable effect of Sc microalloying refines the grain size and the size of primary phase particles and reduces eutectic cell dimensions to 10–15 μ m. Long-term homogenization annealings used in conventionally cast materials lasting several tens of hours followed by a necessary dimension reduction through rolling/extruding could be substituted by energy and material-saving procedure. It consists of two-step short annealings at 300 °C/30 min and 450 °C/30 min, followed by the refinement and hardening of the structure using constrained groove pressing. A dense dispersion of 10–20 nm spherical Al 3 (Sc , Zr) precipitates intensively forms during this treatment and effectively stabilizes the structure and inhibits the grain growth during subsequent solution treatment at 530 °C/30 min. Small (3%) pre-straining after quenching assures more uniform precipitation of strengthening Al 2 Cu ( θ ′ ), Al 2 CuMg ( S ′ ), and Al2CuLi ( T 1 ) particles during subsequent age-hardening annealing at 180 °C/14 h. The material does not contain a directional and anisotropic structure unavoidable in rolled or extruded sheets. The proposed procedure thus represents a model near net shape processing strategy for manufacturing lightweight high-strength sheets for cryogenic applications in aeronautics. [ABSTRACT FROM AUTHOR]

Presently, the formation of oxide films on the surface of Ti-based bipolar plates results in decreased electrical conductivity. This limitation frequently curtails the operational lifespan of proton exchange membrane fuel cells (PEMFCs). In this study, we engineered Ti alloy bipolar plate materials using an elemental screening process and validated their performance through experimentation. The elemental screening results identified eight elements, specifically Ni, Cr, Mo, Ta, W, Fe, Co, and Zn, as promising candidates for bipolar plate materials. Among these, Mo exhibited a pronounced affinity for incorporation into the TiO 2 oxide film. Conductivity measurements of passivated bipolar plates indicated that the Ti–Mo alloy displayed excellent electrical conductivity (1.699 × 1020 Ω m−1). Notably, the introduction of Mo (with an energy level of 1.64 eV) significantly reduced the band gap of the oxide film. Importantly, even after continuous potential oxidation for 10,000 s, the interfacial contact resistance (ICR) of Ti-0.35Mo (9.80 mΩ cm2) remained below the threshold set by the American DOE standard (ICR <10 mΩ cm2). Consequently, this research successfully devised a bipolar plate material utilizing a Ti–Mo alloy and proposed an innovative strategy for improving the conductivity of oxide films in bipolar plate materials via an elemental screening approach. [ABSTRACT FROM AUTHOR]

The as-cast [Co40Cr25(FeNi)35−yMoy]100−xCx (x = 0, 0.5, y = 3, 4, 5 at.%) HEAs (high-entropy alloys) were prepared by a vacuum arc melting furnace and were then hot rolled. The effect of C and Mo elements on the microstructure evolution and mechanical properties of HEAs was systematically analyzed. The results showed that when no C atoms were added, the HEAs consisted of FCC + HCP dual-phase structure. In addition, as the Mo content increased, the grain size of the alloy increased from 17 μm to 47 μm. However, only the FCC phase appeared after adding 0.5 at.% carbon in Mo microalloyed HEAs, and the grain size of the Mo4C0.5 HEA decreased significantly. Due to the Mo atom content exceeding the solid solution limit, the carbides of Mo combined with the C element appeared in the Mo5C0.5 HEA. The strength of C and Mo microalloyed HEAs significantly increased compared to HEAs with no C added. However, the Mo4C0.5 HEA exhibited excellent comprehensive mechanical properties, which was superior to a majority of reported HEAs and conventional metal alloys. Its yield strength, tensile strength, and elongation were 757 MPa, 1186 MPa, and 69%, respectively. The strengthening mechanism was a combination of fine grain strengthening, TWIP effect, and solid solution strengthening. [ABSTRACT FROM AUTHOR]

Increasing the operating temperature and pressure of an automotive engine and reducing its weight can improve fuel efficiency and lower carbon dioxide emissions. These can be achieved by changing the engine piston material from conventional aluminum alloy to high-strength heat-resistant steel. American Iron and Steel Institute 4140 modified steels (AISI 4140 Mod.s), which have improved strength, oxidation resistance, and wear resistance at high temperature were developed by adjusting the AISI 4140 alloy compositions and optimizing the heat treatment process for automotive engine applications. In this study, the effects of modifying alloy compositions on the microstructure, mechanical properties (both at room and high temperatures), and oxidation of AISI 4140 Mod.s were investigated. Effective grain refinement occurred due to the influence of high-temperature stable carbide forming elements such as Mo, and V. The bainite structure changed to martensite structure under the influence Cr and Ni. As the Cr and W contents increased, the oxidation resistance was improved, and the oxide layer thickness decreased after 10 hours exposure at 500°C. The AISI 4140 Mod. exhibited a 35% improvement in room temperature strength, 70% improvement in high-temperature strength, and 40% improvement in high-temperature oxidation resistance compared to conventional AISI 4140. [ABSTRACT FROM AUTHOR]

The microstructures and mechanical properties of Fe–24Mn–10Al–6Ni–1C steels microalloyed by Nb, Mo, and Nb–Mo coaddition in both solid solution and aging states are evaluated. The results show that the addition of Nb, Mo, or Nb–Mo leads to a decrease in austenitic grain size and a suppression in κ‐carbides precipitation during aging. Besides, Mo slightly promotes precipitation of both B2 bands and particles as a ferrite stabilizer. However, Nb and Nb–Mo increase the volume fraction of B2 particles together with decreasing B2 bands due to the formation of NbC and (Nb, Mo)C. The strengths and ductility are improved simultaneously after adding microalloying elements. The coaddition of Nb–Mo achieves a best combination of strength and ductility. After aging, the precipitation of κ‐carbides and B2 leads to a further enhancement in yield strength but a reduction in plasticity for all the experimental steels. Additionally, the effect of Nb/Mo on the strain hardening behavior is also analyzed. [ABSTRACT FROM AUTHOR]

Scandium is the best alloying element to improve the mechanical properties of industrial Al-Si-Mg casting alloys. Most literature reports devote to exploring/designing optimal Sc additions in different commercial Al-Si-Mg casting alloys with well-defined compositions. However, no attempt to optimize the contents of Si, Mg, and Sc has been made due to the great challenge of simultaneous screening in high-dimensional composition space with limited experimental data. In this paper, a novel alloy design strategy was proposed and successfully applied to accelerate the discovery of hypoeutectic Al-Si-Mg-Sc casting alloys over high-dimensional composition space. Firstly, high-throughput CALculation of PHAse Diagrams (CALPHAD) solidification simulations of ocean of hypoeutectic Al-Si-Mg-Sc casting alloys over a wide composition range were performed to establish the quantitative relation 'composition-process-microstructure'. Secondly, the relation 'microstructure-mechanical properties' of Al-Si-Mg-Sc hypoeutectic casting alloys was acquired using the active learning technique supported by key experiments designed by CALPHAD and Bayesian optimization samplings. After a benchmark in A356-xSc alloys, such a strategy was utilized to design the high-performance hypoeutectic Al-xSi-yMg alloys with optimal Sc additions that were later experimentally validated. Finally, the present strategy was successfully extended to screen the optimal contents of Si, Mg, and Sc over high-dimensional hypoeutectic Al-xSi-yMg-zSc composition space. It is anticipated that the proposed strategy integrating active learning with high-throughput CALPHAD simulations and key experiments should be generally applicable to the efficient design of high-performance multi-component materials over high-dimensional composition space. [ABSTRACT FROM AUTHOR]

This study aims to investigate the combined effect of niobium (Nb) microalloying and austenite grain refinement, using a specific heat treatment cycle, on the microstructure and tribological properties of Armox 500T steel. In this work, Nb addition and thermal cycling were utilized for grain refinement and enhancement of the mechanical properties of Armox 500T alloy, to provide improved protection via lightweight armor steel components with a high strength-to-weight ratio. The kinetics of transformation of the developed Armox alloys were studied using JMATPro version 13.2. The samples were subjected to two austenitizing temperatures, 1000 °C and 1100 °C, followed by 4 min of holding time and three consecutive thermal and rapid-quenching processes from 900 °C to room temperature. Scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) was employed to analyze the microstructure, which primarily consists of four types of martensite: short and long lath martensite, blocky martensite, and equiaxed martensite. Additionally, a small percentage (not exceeding 3%) of carbide precipitates was observed. The wear characteristics of the investigated alloys were evaluated using a pin-on-disc tribometer. The results demonstrate that alloying with Nb and grain refinement using a thermal cycle significantly reduce the wear rate. [ABSTRACT FROM AUTHOR]

The surface layer of 8407 die steel was strengthened using the combination of ultrasonic surface rolling and high-energy ion implanting in the present work. The strengthened layer was then characterized via microstructure observation, composition analysis, and hardness test. After that, the frictional wear and thermal fatigue properties of high-energy ion implanting specimens and composite-reinforced specimens were compared. Results show that the pretreatment of specimens with ultrasonic surface rolling causes grain refinement in the material surface, which promotes the strengthening effect of high-energy ion implanting. The wear volume of composite-reinforced specimens at medium and high frequencies is reduced by about 20%, and the wear resistance of these specimens is significantly improved with a lower friction coefficient and wear volume at moderate and high frequencies in alternating load friction experiments. Meanwhile, the thermal fatigue crack depth of composite-reinforced specimens is reduced by about 47.5%, which effectively prevents the growth of thermal cracks in the surface, thus improving the curing ability of the implanted elements. Therefore, composite strengthening of the mold steel surface is conducive to improving the cycle life, ensuring accuracy, effectively hindering the expansion of thermal cracks, and saving the cost of production. [ABSTRACT FROM AUTHOR]

Dual-phase high-entropy alloys with excellent room temperature and high-temperature properties have been widely studied as potential high-temperature structural materials. However, interface weakening causes its high-temperature performance to decline at higher temperatures, severely limiting further development. In this study, a series of Al17Cr10Fe36Ni36Mo1Hfx (x = 0, 0.03, 0.15, 0.3, 0.5, and 0.8 at%) alloys were prepared to study the effect of Hf content on the microstructure and mechanical properties of the matrix alloy. The results indicate that with the addition of the Hf, the Hf-rich phase began to precipitate at the interface and inside the B2 phase in the matrix alloy. In contrast, the morphology of both the FCC and B2 phases had no noticeable change. With the increase in Hf content, the high-temperature strength and ductility of the alloy first increased and then decreased, while the room temperature performance remained almost unchanged. Benefiting from the hindrance of the Hf-rich phase to grain boundary sliding and dislocation movement during high-temperature deformation, the tensile strength, yield strength, and plasticity of the matrix alloy increased from 474 MPa, 535 MPa, and 8.7% to 816 MPa, 923 MPa, and 42.0% for the Al17Cr10Fe36Ni36Mo1Hf0.5 alloys, respectively. This work provides a new path for designing a high-entropy alloy with excellent high-temperature mechanical properties. [ABSTRACT FROM AUTHOR]

Herein, the Fe–5Mn–2Al–0.1C (wt%) and micro‐alloyed Fe–5Mn–2Al–0.1C–0.1Nb–0.2V (wt%) medium Mn steels are processed by a novel flash‐austenite‐reverse‐transformation (ART) annealing. The core–shell Mn‐gradient in austenite is observed and compositionally characterized at near‐atomic scale by using atom probe tomography. Compared with the conventional ART annealing, flash‐ART process doubled the austenite fraction in both materials, based on electron backscattering diffraction measurement. The rapid austenite reversion in flash‐ART annealed MMnS is attributed to the negligible partitioning local equilibrium controlled austenite kinetics at the flash temperature. The formation of core–shell Mn‐gradient is due to the different austenite growth kinetics and interface mobilities. Microalloying elements are found to form nano‐carbides, which leads to decelerating austenite reversion because of depleted carbon content in the initial martensitic microstructure, and retarding austenite growth according to pinning effect. [ABSTRACT FROM AUTHOR]

This work demonstrates that Cd microadditions can enhance the precipitation of age-hardening precipitates in 2xxx and 6xxx alloys as well as the dispersoid precipitation in 3xxx alloys, but have a minimal effect on the precipitation in 7xxx alloys. Experimental and theoretical methods are utilised to investigate the nucleation and precipitation of precipitates/dispersoids in Cd-containing Al alloys. The enhanced precipitation of θ′ and α-dispersoids in 2xxx and 3xxx alloys, respectively, are proposed to result from the heterogeneous nucleation on earlier-formed Cd-rich nanoparticles, while the enhanced precipitation of β′′ in 6xxx alloys is attributed to the increased number density of effective Mg-Si co-clusters due to the Cd incorporation. This investigation provides theoretical basis for the design of precipitation-strengthened Al alloys via microalloying. [ABSTRACT FROM AUTHOR]

While hydrogen microalloying in metallic alloys has been extensively investigated, the failure mechanism underlying the H-alloyed metallic glasses (MGs) remains elusive. Here, atomistic simulations are performed on the tensile failure of H-free and H-alloyed notched MGs. An intriguing transition in failure mechanism from shear banding to cracking occurs after hydrogen microalloying. A theoretical model based on the concept of energetic model is then proposed to rationalize this deformation mode transition. Cracking behavior is more significant with increasing H content, agreeing well with the simulation results. These results advance our understanding of failure mechanism in H-alloyed MGs. [ABSTRACT FROM AUTHOR]

To improve the stress relaxation resistance of the Cu-5Ni-S8n alloy, the effects of Co or P addition on its stress relaxation resistance were investigated by scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction), X-ray diffraction, and high-temperature creep durability tester. The results revealed that the relaxation rate increased dramatically as the temperature rose. The thermal stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition; After 100 h of stress relaxation tests at 200°C or 250°C, the residual stress value of the Cu-15Ni-8Sn alloy increased by 23 MPa or 22 MPa with Co addition, which was associated with the consumption of vacancies by Co atoms and the pinning effect of Co atoms on dislocation. However, at 250°C, the stress relaxation resistance of the Cu-15Ni-8Sn-0.2P alloy was lower than that of the Cu-15Ni-8Sn alloy. This difference was due to the inclusion of P, which promoted the recrystallization reaction. Article highlights Recrystallization and the decrease of dislocation density are the major reasons for the stress relaxation of the samples. The stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition. The addition of the P element is not conducive to the improvement of thermal stress relaxation resistance. [ABSTRACT FROM AUTHOR]

Two groups of steels industrially smelted differing in carbon and manganese content, as well as microalloying elements, are studied. It is established that an increase in carbon content does not adversely affect oilfield pipe steel corrosion resistance. Provision of the required strength level may be achieved by increasing the carbon and manganese contents, which is also expedient from an economic point of view. At the same time, absence of unfavorable structural components in steel and steel low contamination with nonmetallic inclusions of an unfavorable composition ensures a high level of steel corrosion resistance. [ABSTRACT FROM AUTHOR]

Achieving strength-ductility synergy of hot-stamping steel via microalloying technology has attracted great attention due to their pronounced precipitation strengthening. Nevertheless, the precipitation behaviours and characteristics have not been clearly unveiled. In this work, the effects of V content on the microstructure and mechanical properties of 1800 MPa grade hot-stamping steel are systematically studied. Massive V contained precipitates develop after hot-rolling and coiling, which refine the martensitic microstructure and retain in the matrix after austenitizing and quenching. The refined martensite with massive precipitates is responsible for the good mechanical properties. Generally, the tensile strength decreases slightly with increasing V content from 0.04% to 0.2%, as V consumes C in the martensite matrix by forming carbides and promoting precipitate coarsening. [ABSTRACT FROM AUTHOR]

This study investigated the simultaneous effect of adding lithium and severe plastic deformation on Al–Cu–Mg alloy's microstructure, mechanical property, and corrosion resistance. The results showed that under the influence of the dynamic recrystallization executed in the thermo-mechanical process, the initial coarse dendritic structure was replaced by the fine and equiaxed structure. Moreover, adding lithium in amounts less than 0.5 wt% did not have a noticeable effect on the grain size of the extruded alloy. In both series of cast and extruded samples, adding lithium caused a slight change in texture parameters. In the extruded samples, the intensity of the {110} texture was slightly reduced, and the {100} and {111} textures were strengthened compared to the cast sample. Increasing the lithium content in the aluminum intensified the relative amount of lithium in the S-Al2Cu (Li, Mg) precipitate. The formation of fine GPB zones and {100} texture enhancement resulted in high strength and elongation. By increasing lithium up to 0.5 wt% on Al–Cu–Mg alloy, the corrosion potential and current density decreased 67 and 51%, respectively. [ABSTRACT FROM AUTHOR]

This work explored a new idea for enhancing the resistance to stress corrosion cracking (SCC) of mining anchor steel through microalloying. Microalloyed anchor steels with Nb, Cu, Ni, Sb, and C were prepared through vacuum smelting and hot rolling. Electrochemical measurements, slow strain rate tensile (SSRT) tests, and fracture morphology observations were used to study the electrochemical and SCC behavior in the simulated mine environment. The results proved that the microstructure of microalloyed steels varies slightly. Adding Ni, Cu, and Sb can improve the mechanical properties of the anchor steel, while reducing C content decreases tensile strength as a result of loss of the solution-strengthening effect. The addition of Sb, Cu, Ni, and reducing the content of C enhances the resistance to corrosion and SCC by mitigating anodic dissolution (AD), while adding Nb improves SCC resistance by inhibiting hydrogen embrittlement (HE). The combined addition of 1% Ni, 0.5% Cu, 0.05% Nb, 0.1% Sb, and 0.5% C presented the highest SCC resistance, which is a promising prospect for the development of high-performance, low-alloy anchor steels. The combined addition of 1% Ni, 0.5% Cu, 0.05% Nb, and 0.1% Sb resulted in the inhibition of electrochemical reactions and corrosion. As a result of the synergistic effect of the microalloy, both AD and HE mechanisms were simultaneously inhibited, which greatly enhanced SCC resistance. [ABSTRACT FROM AUTHOR]

Cu–15Ni–8Sn alloy is the best choice to replace beryllium bronze alloy. This alloy has unparalleled application value in aerospace, ocean engineering, electronic information, equipment manufacturing, and other fields. However, the application of Cu–15Ni–8Sn alloy is challenged and limited because of a series of problems in its preparation and processing, such as easy segregation, difficult deformation, and discontinuous precipitation. It is an effective way to improve the comprehensive properties of Cu–15Ni–8Sn alloy using alloying design and process optimization to control the as-cast, deformed, and heat-treated microstructures. At present, it is a hot spot for scholars to study. In this paper, the grade generation, system evolution, and preparation technology development of Cu–15Ni–8Sn alloy are comprehensively reviewed. The phase transformation sequence of the Cu–15Ni–8Sn alloy is discussed. The influence of the type, amount, and existing form of alloying elements on the strength of Cu–15Ni–8Sn alloy and its mechanism are systematically summarized. Furthermore, the latest research progress on the effects of solid solution, cold deformation, and aging on the phase structure transformation and mechanical properties of Cu–15Ni–8Sn alloy is summarized. Finally, the future development trend of the Cu–15Ni–8Sn alloy is projected. The research results of this paper can provide a reference for the control of the microstructure and properties of high-performance Cu–15Ni–8Sn alloys used in key fields, as well as the optimization of the preparation process and alloy composition. [ABSTRACT FROM AUTHOR]

Low-cycle fatigue testing was carried out for the welded joints of constructional steels containing 0% V + 0.0021% N and 0.10% V + 0.0078% N, and the effects of V-N microalloying on the low-cycle fatigue property of the welded joints were investigated. The results showed that when the total strain amplitudes were 1.2%, 1.4% and 1.6%, the mean low-cycle fatigue lives of the welded joints of steel containing 0.10% V + 0.0078% N were 5050, 2372 and 1535 cycles, respectively, which were significantly higher than those of the welded joints of steel containing 0% V + 0.0021% N; however, when the total strain amplitudes increased to 1.8% and 2.0%, the mean low-cycle fatigue lives of the welded joints of steel containing 0.10% V + 0.0078% N were 575 and 367 cycles, respectively, which were gradually lower than those of the welded joints of steel containing 0% V + 0.0021% N. The reasons causing the difference of low-cycle fatigue life were explained by the dislocation structure and precipitates in the welding heat-affected zone, plastic strain energy density of the welded joints, and fatigue fracture morphology. When the low-cycle fatigue life is between 100 and 200 cycles, the cyclic toughness of the welded joint of steel containing 0.10% V + 0.0078% N is between 57.48 and 78.22 J/cm3, which is higher than that of the welded joint of steel containing 0% V + 0.0021% N, indicating that the welded joint of steel containing 0.10% V + 0.0078% N is able to absorb more energy in a seismic condition, therefore possessing better seismic resistance. [ABSTRACT FROM AUTHOR]

In order to improve the performance of metal deposited with PP-Np-50Kh2MNSGF flux-cored wire, boron-containing FKhB-1 binder was added to the wire charge in such a way as to obtain boron content on the level of 0.01 % in the deposited metal. The effect of adding FKhB-1 binder to the flux-cored wire charge on its welding-technological properties was studied experimentally. It was found that application of boron-containing binder in the flux-cored wire charge does not impair its welding-technological properties, boron microalloying leading to refinement of the deposited metal structure and increases its hardness from HRC 53…57 to HRC 60…62 at the same content of other alloying elements. Developed PP-Np-50Kh2MNSGF flux-cored wire is proposed for deposition of wear-resistant layers for protection of parts of special machines and mechanisms in mining, metal-lurgical and other industries, operating under the difficult conditions of abrasive wear in combination with intense shock loads. [ABSTRACT FROM AUTHOR]

To investigate Bauschinger effect in metastable high-entropy alloys with strain-induced FCC → HCP phase transformation, we designed a series of Gd micro-alloying non-equiatomic metastable high-entropy alloys. The results show that all tested alloys have asymmetrical tension-compression properties exhibiting the obvious Bauschinger effect, which is related to the different levels of phase transformation in compression and tension owing to different deformation textures. Excessive phase transformation suppresses the increase in pile-up density of geometrically necessary dislocations (GNDs), resulting in a back stress relaxation effect. The inverse phase transformation observed by quasi in-situ EBSD proves the instability of the HCP phase. The established kinetic model points out limitation of the classical back stress measurement method in metastable high-entropy alloys. [ABSTRACT FROM AUTHOR]

Herein, non‐quenched and tempered forging steels containing V and V–Nb are designed, and the mechanical properties and microstructure of two steels are compared and analyzed. The comprehensive mechanical properties of V–Nb containing steel are as follows: the yield strength is 525.1 MPa, the impact energy AkV is 62.1 J at ambient temperature, and the elongation is 26.1%. It is shown in the results that the addition of Nb element can refine the grain size (17.2 μm), increase the ferrite content (54.1%), and refine the lamellar spacing of pearlite (274 nm). The formation of V (C, N) particles on MnS inclusions can promote fine ferrite nucleation and growth, and Nb element can further promote ferrite nucleation by forming coarser (V, Nb) (C, N) particles. The difference of yield strength and hardness between the two steels is mainly caused by the difference of precipitation strengthening, the precipitation‐strengthening increment of V–Nb containing steel is 18.31 MPa higher than that of V containing steel, which is because the coarser‐size (V, Nb) (C, N) particles produce stronger precipitation‐strengthening effect. But the large‐sized MnS inclusions are beneficial to the increase of crack driving force and reduce the plasticity and toughness. [ABSTRACT FROM AUTHOR]

During heat treatment, gear steels undergo grain coarsening, so an appropriate heat treatment process that can efficiently control the austenite grain growth and ensure a good performance of gear steels is particularly important. Herein, the influence of a requenching treatment on the comprehensive behavior of low‐carbon alloy steel 20Cr2Ni4 is explored. The pristine steel samples with and without Nb microalloying subjected to conventional quenching and tempering (QT) treatment are compared with the requenched steel sample. The results show that different requenching temperatures considerably impact grain refinement and homogenization. The steel requenched at 830 °C exhibits the greatest tensile strength of 1444 MPa and excellent toughness, comparable to the mechanical properties of the steel upon Nb microalloying after the conventional QT treatment. The formation of twin martensite and uniform fine grains with a high dislocation density together with numerous low‐angle and high‐angle grain boundaries is responsible for the simultaneously improved strength and ductility of the requenched specimen; thus, the proposed requenching heat treatment is a promising, efficient, and reliable method to double‐refine prior austenite grains and their packet and block structures and improve the comprehensive properties with a combination of high strength and toughness, yielding high‐strength gear steel. [ABSTRACT FROM AUTHOR]

Considerable interest to improve magnetic entropy change (Δ S m ) and broaden working temperature interval (WTI) of NiMnGa ferromagnetic shape memory alloys (FESMAs) was stimulated by their applications as promising candidate materials for solid-state refrigeration. In the present study, we presented an approach to enhance the magnetocaloric properties of polycrystalline NiMnGa FESMAs via combining Dy micro-alloying and pseudoelastic cyclic training. The introduction of Dy elements established stable magneto-structural coupling transformation from the paramagnetic austenite to ferromagnetic martensite, accompanied by a large Δ S m [−16.42 J/(kg K)] and a widened WTI (∼15.98 K). Fascinatingly, it was demonstrated that the internal strain fields at phase interface between matrix and DyNi4Ga precipitates could assist the phase transformation nucleation, which significantly reduced the hysteresis loss from 20.84 J/kg of Ni54Mn25Ga21 alloy to 8.14 J/kg of Ni54Mn25Ga20.7Dy0.3 alloy. More importantly, the subsequent pseudoelastic cyclic training produced a strong ⟨ 110 ⟩ NM preferred crystallographic orientation, which facilitated the magnetic alignment along easy magnetization axis. Consequently, the giant Δ S m value up to −24.25 J/(kg K) and effective refrigeration capacity RCeff of 198.77 J/kg were further achieved in the trained Ni54Mn25Ga20.7Dy0.3 alloy under an external magnetic-field change of 5.0 T. [ABSTRACT FROM AUTHOR]

The deformation resistance would be increased with the addition of Nb and Ti, which makes it difficult to accurately control the rolling process, resulting in mixed grains and cracks. The hot deformation behavior of Nb–Ti microalloyed high strength steel was investigated in the temperature range of 900–1100 °C with the strain rate between 0.1 and 5 s−1. The recrystallization active energy was obtained by regression calculation, and the thermal deformation equation was established. The dynamic recrystallization critical strain model was established by changing the work hardening rate. The results show that a higher deformation temperature and lower strain rate are conducive to dynamic recrystallization. The active energy of dynamic recrystallization is 386.30 kJ mol−1, εp = 1.23 × 10−2Z0.087, and εc = 1.95 × 10−3Z0.111. The high strength steel is strengthened by the strengthening of grain refining and precipitation of Nb–Ti microalloys. The second phase particles are TiN with a size of about 100 nm, (Nb, Ti)C with the size between 50 and 80 nm, and NbC with the size between 10 and 20 nm. [ABSTRACT FROM AUTHOR]

Comparative analysis of the effect of microalloying with niobium, vanadium and titanium on the processes of structure formation in low-alloy low-carbon steels subjected to hot plastic deformation by controlled rolling is performed. The concentration and temperature ranges of the influence of these elements on formation of austenite preceding the hot plastic deformation or occurring in the final stage of the controlled rolling before the start of polymorphic γ → α transformation are determined. It is shown that the inhibitory effect of the microalloying elements on the growth of the austenite grains in heating in the γ -range intensifies in the V → Nb → Ti order, and the capacity to retard recrystallization of the hot-deformed austenite intensifies in the V → Ti → Nb order. The microadditions of niobium are shown to have a dual effect on the kinetics of the polymorphic γ → α transformation. [ABSTRACT FROM AUTHOR]

In this research, the structural state and mechanical properties of nine pilot batches of HC340LA cold-rolled steel, annealed in bell-type furnaces from the steel of two melts of different compositions using Nb or Ti microalloying, were studied. From the obtained results, the uniformity and stability of the structure and properties of rolled products were significantly improved both in each pilot batch and in the transition from batch to batch compared with those of mass-produced cold-rolled steel grade HC340LA while reducing costs. Methods for further improving the efficiency of the integrated technology for the production of HC340LA rolled products according to EN 10268 were determined. [ABSTRACT FROM AUTHOR]

This study investigated the effect of Li micro-alloying on microstructure, mechanical properties, and corrosion resistance of artificially aged Al–Cu–Mg alloy with different Cu:Mg ratios. The Al–Cu–Mg alloy properties were studied after two non-isothermal and isothermal aging treatments. The results show that adding Li does not cause a noticeable change in the number of precipitates formed in the microstructure of Al–Cu–Mg alloy. Also, by increasing the Cu:Mg ratio from 1 to 3.8 in the alloy containing 0.25 wt% of lithium, the maximum hardness and tensile strength increased by 6% and 4%, respectively. With the addition of lithium up to 0.25 wt%, the size of the S and θ precipitates has become smaller and dispersed throughout the microstructure. By increasing the amount of lithium to the value of 0.25 wt%, it can be seen that in two alloys with the copper to magnesium ratio equal to 1 and 3.8, the corrosion current density changes from 5.14 × 10−4 to 4.89 × 10−4 A.Cm−2, and corrosion resistance increases 30%. By comparing the corrosion current density of different samples, the NIA treatment results in at least 18% lower corrosion current density than the isothermal aging treatment. [ABSTRACT FROM AUTHOR]

To optimize the composition of steel in the work aims to identify the minimum required number of chemical elements and their content to avoid overheating and unnecessary economic costs. The solution is proposed in the form of microalloying, which leads to grinding of austenitic grains, and after phase transformation and ferritic grains, which improves the properties of steel. The established regularities allowed to quantitatively substantiate the chosen optimal chemical composition of steel, namely to establish the limit of variation of microalloying elements - chromium, vanadium and titanium. It was found that the obtained steel in comparison with the prototype has higher values of impact strength, while maintaining high strength and fluidity. Thus, the combination of improved service and mechanical properties of steel helps to increase the service life of its products. [ABSTRACT FROM AUTHOR]

The effect of Sr on the microstructure of Al–4.6Mg alloy is studied via optical microscopy, scanning electron microscopy‐energy‐dispersive analysis, electron backscattered diffraction, transmission electron microscopy, and the intergranular corrosion susceptibility is evaluated according to ASTM G67. The main precipitation phases of Al–4.6Mg alloy are β‐Al3Mg2 and Al6Mn, with a new square phase of Al3Mn also being formed. After the addition of Sr, the β‐Al3Mg2 phase of the alloy decreases, the morphology changes, and Al4Sr and τ‐Al38Mg58Sr4 phases are formed. Accordingly, the nanoscale precipitation phase τ‐Al38Mg58Sr4 is uniformly distributed inside the grains. Microstructure analysis shows that Sr promotes the dynamic recovery and dynamic recrystallization of the alloy, inhibits the growth of recrystallized grains, and reduces the alloy grain size from 14.294 to 10.273 μm. Additionally, the low‐angle grain boundaries increase, the high‐angle grain boundaries decrease, the texture of the rotated cube r‐{001}<110> improves, and the deformation texture decreases. The IGC susceptibility of the alloy is reduced with the addition of Sr, and the corrosion resistance in an electrolyte containing NaCl is enhanced. [ABSTRACT FROM AUTHOR]

In this paper, the progress of the test methods and characterization approaches of aluminum alloys hardenability was reviewed in detail. The test method mainly included the traditional end-quenching method and the modified method. While the characterization approaches of alloy hardenability consist mainly of ageing hardness curves, solid solution conductivity curves, ageing tensile curves, time temperature transformation (TTT) curves, time temperature properties (TTP) curves, continuous cooling transformation (CCT) curves, and advanced theoretical derivation method have appeared in recent years. The hardenability testing equipment for different tested samples with different material natures, engineering applications properties, and measurement sizes was introduced. Meanwhile, the improvement programmed proposed for shortcomings in the traditional hardenability testing process and the current deficiencies during the overall hardenability testing process were also presented. In addition, the influence factors from the view of composition design applied to the hardenability behaviors of Aluminum alloys were summarized. Among them, the combined addition of micro-alloying elements is considered to be a better method for improving the hardenability of high-strength aluminum alloys. [ABSTRACT FROM AUTHOR]

Medium manganese steels fall into the category of modern third-generation high-strength steels. Thanks to their alloying, they use a number of strengthening mechanisms, such as the TRIP and TWIP effects, to achieve their mechanical properties. The excellent combination of strength and ductility also makes them suitable for safety components in car shells, such as side reinforcements. Medium manganese steel with 0.2% C, 5% Mn, and 3% Al was used for the experimental program. Sheets with a thickness of 1.8 mm without surface treatment were formed in a press hardening tool. Side reinforcements require various mechanical properties in different parts. The change in mechanical properties was tested on the produced profiles. The changes in the tested regions were produced by local heating to an intercritical region. These results were compared with classically annealed specimens in a furnace. In the case of tool hardening, strength limits were over 1450 MPa with a ductility of about 15%. [ABSTRACT FROM AUTHOR]

Porosity is a major concern in the manufacturing of MAX phase components through powder bed fusion process. Three factors, powder characteristics, processing parameters, and internal reactions have been identified as key factors governing densifications of these printed parts. While investigations on the first two factors are quite common, the last one seems less explored. In this study, micro‐alloying (substitution) on the M‐site was selected as a possible way of tuning the internal reaction. A lower diffusion material niobium was adopted as a substitutional component through the relation (2−x)Ti:(1+x)Al:C:yNb$(2 - x){\rm{Ti}}:(1 + x){\rm{Al}}:{\rm{C}}:y{\rm{Nb}}$,that combine three pre‐existing concepts on powder mixture, including stoichiometric, near‐stoichiometric, and the solid solution on M‐site. Two powder mixtures in prescribed ratio related to two different combinations of x and y values arbitrarily chosen denoted by Nb1 and Nb3 were considered for investigation. A comparison of density and area fraction quantifying the distribution of pores and compact areas on the upper surface of the sample was made. A skeletal density of 94.85% and a compact area fraction of 68.24% were outstanding characteristics displayed in the Nb1 and Nb3 series, respectively, with a significant dependence on the processing parameters. The advantages and disadvantages of these two powder mixtures are discussed. [ABSTRACT FROM AUTHOR]

High-strength press-hardened steels (PHS) are highly desired in the automotive industry to meet the requirement of carbon neutrality. This review aims to provide a systematic study of the relationship between multi-scale microstructural tailoring and the mechanical behavior and other service performance of PHS. It begins with a brief introduction to the background of PHS, followed by an in-depth description of the strategies used to enhance their properties. These strategies are categorized into traditional Mn-B steels and novel PHS. For traditional Mn-B steels, extensive research has verified that the addition of microalloying elements can refine the microstructure of PHS, resulting in improved mechanical properties, hydrogen embrittlement resistance, and other service performance. In the case of novel PHS, recent progress has principally demonstrated that the novel composition of steels coupling with innovative thermomechanical processing can obtain multi-phase structure and superior mechanical properties compared with traditional Mn-B steels, and their effect on oxidation resistance is highlighted. Finally, the review offers an outlook on the future development of PHS from the perspective of academic research and industrial applications. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of a novel Cr and Si co-alloying Fe–0.6C–15Mn steels, labeled as 2Cr(3Si), 4Cr(3Si), 6Cr(3Si), and 4Cr(0Si), were investigated. All samples for mechanical property test and microstructure analysis were subjected to solution treatment at 1100 °C for 1 h after forging. The results indicate that the microstructure for the 2Cr(3Si), 4Cr(3Si) and 4Cr(0Si) steels mainly consists of the full austenite, and grain size is about 100 μm, whereas the microstructure of the 6Cr(3Si) steel exhibits austenite and some undissolved Cr7C3 carbides. The refined austenite grain size of 48 μm is obtained in 6Cr(3Si) steel. The strength and elongation of the experiment steels with Si and Cr increase significantly with the Cr contents. Among the steels, the 6Cr(3Si) steel has the maximum yield strength, tensile strength and elongation of 490 MPa, 987 MPa and 41.5%, respectively. And the impact toughness is 151 J cm−2. The Si-free steel (4Cr(0Si)) exhibits a low yield strength (372 MPa) and a high tensile strength (992 MPa). The high elongation of 74.8% and impact toughness of 320 J cm−2 are obtained. The results also demonstrate that the Cr and Si co-alloying in high-Mn steels is beneficial to improve work hardening capability, and the work hardening capability increases with the increase of Cr content. According to the results analyzed by the electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), the strain-induced ε-martensite is dominant at the low strain level and the content of ε-martensite increases with the increase of the tensile strain. The maximum amount of the ε-martensite is found in the 6Cr(3Si) steel. With the strain increasing, α'-martensite appears in microstructure, which is formed on the ε-martensite. In addition, the stacking faults (SF) and mechanical twins (MT) are also observed. [ABSTRACT FROM AUTHOR]

For manufacturing HC340LA cold-rolled steel annealed in bell-type furnaces from two melt steel of different compositions using Nb or Ti microalloying, metal samples were studied from nine experimental batches of hot-rolled semi-finished stocks. Based on the results, the efficiency of the developed principles for improving the existing technology to enhance the properties and quality of steel is substantiated while reducing production costs. [ABSTRACT FROM AUTHOR]

Thermo-mechanical fatigue (TMF) is one of the most detrimental failures of critical engine components and greatly limits their service life. In this study, the out-of-phase TMF (OP-TMF) behavior in Al-Si-Cu 319 cast alloys microalloyed with Mo was systematically investigated under various strain amplitudes ranging from 0.1–0.6% and temperature cycling at 60–300 °C and compared with the base 319 alloy free of Mo. Cyclic stress softening occurred in both experimental alloys when applying the TMF loading, resulting from the coarsening of θ'-Al2Cu precipitates. However, the softening rate of the Mo-containing alloy was lower than that of the base 319 alloy because of its lower θ'-Al2Cu precipitate coarsening rate per cycle. The Mo-containing alloy exhibited a longer TMF lifetime than the base alloy at the same strain amplitude. Microalloying 319 alloy with Mo enhanced the TMF resistance mainly by slowing the coarsening of θ'-Al2Cu precipitates and providing supplementary strengthening from thermally stable Mo-containing α-dispersoids distributed in the Al matrix. The energy-based model was successfully applied for predicting the TMF lifetime with a low life predictor factor, which agreed well with the experimentally measured fatigue cycles. [ABSTRACT FROM AUTHOR]