Good Combination Of Strength Research Articles

Grain boundary migration hysteresis during recrystallization of IN738LC alloy fabricated via laser powder bed fusion

The metastable microstructure formed during laser powder bed fusion (LPBF) significantly influences recrystallization behavior, which is crucial for flexible control of microstructure. To investigate these effects, various IN738LC alloys were fabricated by adjusting the volume energy density (VED) and then subjected to the same hot isostatic pressing (HIP) treatment. The microstructures before and after heat treatment were systematically analyzed using multi-scales characterization methods. The results indicate that the recrystallization fraction in HIP-treated samples decreased from 75% to 24% as the VED increased from 53 J/mm3 to 125 J/mm3. This reduction is primarily attributed to the increased grain boundary migration hysteresis caused by the higher density and larger diameter of MC-type carbide particles (i.e., MC particles). Subsequently, these HIP-treated samples were further processed using standard heat treatment (SHT) to evaluate their tensile properties at 23 °C and 900 °C. At 23 °C, the sample with the lowest recrystallization fraction (VED = 125 J/mm3) exhibited the best combination of strength and ductility, with an ultimate tensile strength (UTS) of 1422 MPa, yield strength (YS) of 932 MPa, and elongation of 21%. At 900 °C, the sample with a medium recrystallization fraction (VED = 75 J/mm3) demonstrated the best combination of strength and ductility, with an UTS of 626 MPa, YS of 420 MPa, and elongation of 15.5%.

Non-Equal Contributions of Different Elements and Atomic Bonds to the Strength and Deformability of a Multicomponent Metallic Glass Zr47Cu46Al7

Multicomponent metallic glasses (MGs) are a fascinating class of advanced alloys known for their exceptional properties such as limit-approaching strength, high hardness and corrosion resistance, and near-net-shape castability. One important question regarding these materials that remains unanswered is how the different elements and atomic bonds within them control their strength and deformability. Here, we present a detailed visual and statistical analysis of the behaviors of various elements and atomic bonds in the Zr47Cu46Al7 (at%) MG during a uniaxial tensile test (in the z-direction) simulated using molecular dynamics. Specifically, we investigate the identities of atoms undergoing significant shear strain, and the averaged bond lengths, projected z-lengths, and z-angles (angles with respect to the z-direction) of all the atomic bonds as functions of increasing strain. We show that, prior to yielding, the Zr element and the intermediate (Zr-Zr, Cu-Al) and stronger (Zr-Al, Zr-Cu) bonds dominate the elastic deformation and strength, while the Cu and Al elements and the weaker Al-Al and Cu-Cu bonds contribute more to the highly localized shear transformation. The significant reconstruction, as signified by the cessation of bond-length increment and bond-angle decrement, of the intermediate and the stronger bonds triggers yielding of the material. After yielding, all the elements and bonds participate in the plastic deformation while the stronger bonds contribute more to the residual strength and the ultimate (fracture) strain. The results provide new insights into the atomic mechanisms underlying the mechanical behavior of multicomponent MGs, and may assist in the future design of MG compositions towards better combination of strength and deformability.

Microstructure and strength-conductivity synergy of Al-Mg-Si-Cu alloy sheets prepared via vacuum melting and thermo-mechanical treatment

This work has investigated the response of microstructural evolution on the strength and electrical conductivity (EC) of vacuum melted Al-Mg-Si-Cu alloys during T6 heat treatment, cold rolling (CR) and re-aging (RA). The precipitation behavior of nano-scaled precipitates during thermo-mechanical treatment was revealed. The strength- conductivity improvement mechanisms of the alloy were discussed. The results showed that compared with the non-vacuum melting alloy, there were superior enhancements in the strength and EC of the alloy prepared by vacuum melting due to the high compactness. After T6 heat treatment, nanoscale β", Q' and L phases were precipitated in the alloy sheet. Owing to the increased dislocation density and precipitate dissolution during CR, the strength of the alloy sheet was improved, followed by a decrease in EC. After RA, a good combination of strength and EC of the alloy sheet was obtained, i.e., ultimate tensile strength and EC were 350MPa and 57.48% IACS, respectively, which was associated with the formation of nano-sized precipitates and the decrease in solute atom concentration. The precipitates volume, dislocation density, grain refinement and solid solubility during thermo-mechanical treatment were the main factors determining the strength and EC of the alloy. This work provides a strategy for the preparation of high strength-conductivity Al alloys.

Plastic deformation and strengthening mechanisms in CoNiCrFe high entropy alloys: The role of lattice site occupancy

The work herein presents the designing of two γʹ strengthened high entropy alloys guided by density function theory (DFT) and thermodynamics calculations with compositions Co34Ni34Cr12Al8Nb3Ti4Fe5 and Co31.5Ni31.5Cr12Al8Nb3Ti4Fe10 (referred as 5Fe and 10Fe). These alloys in the peak aged condition (900 °C for 20 h) exhibit similar precipitates sizes, shapes, volume fractions and γ/γʹ lattice misfit (∼ 0.56). Intriguingly, despite their microstructural similarities, these alloys show different trends in yield strength (YS) evolution over a temperature range. The 5Fe alloy shows a better combination of strength and ductility at room temperature (RT), with YS and elongation of 970 ± 25 MPa, ∼ 18 (%), respectively, in comparison to 850 ± 20 MPa, and ∼ 15(%) in the 10Fe alloy. The precipitate chemistry analyses carried out by 3D atom probe tomography suggest that Fe atoms occupy B-sites in the 5Fe alloy, while it occupies both A and B-sites in the 10Fe alloy. The site occupancy behaviour rendered a higher stacking fault energy (SFE) of the 5Fe alloy, making the γʹ shearing more difficult compared to the 10Fe alloy. The synchrotron X-ray measurements further confirm higher stacking fault (SF) probability in the γ matrix compared to γʹ precipitates in the 5Fe alloy. The role of deformation substructure evolution is also carefully discussed to explain the differences in the high temperature behavior. These results on the effects of alloying chemistry in high entropy alloys enable tuning the mechanical properties of alloys and widening the alloy spectrum with improved high-temperature properties.

Effect of martensite hardness on mechanical properties and stress/strain-partitioning behavior in ferrite + martensite dual-phase steels

Low-carbon dual-phase (DP) steels composed of ferrite and martensite are widely used in automotive industries due to their good combination of strength and ductility and remarkable strain-hardening ability. Such exceptional mechanical properties of DP steels arise from microstructural deformation heterogeneity due to the different deformation roles of soft ferrite and hard martensite. The present study investigated mechanical properties and local deformation behavior of DP steels having different martensite hardness (strength) using digital image correlation (DIC) technique and in-situ X-ray diffraction (XRD) experiment during tensile deformation. The martensite hardness was reduced by tempering treatment, and its mechanical properties were compared with the as-quenched DP specimen by tensile testing. The tempered DP specimen exhibited reduced strength but enhanced ductility, especially in post-uniform elongation, compared to the as-quenched DP specimen. DIC-strain analysis indicated that the tempering effectively inhibited strain localization, allowing a greater contribution of martensite to plastic deformation. On the other hand, the in-situ XRD analysis revealed that the tempering significantly restricted the stress-increasing potential of martensite. Our results suggest that martensite, acting as a hard domain, plays a significant role in enhancing strain-hardening ability and achieving large uniform elongation due to its high stress-increasing potential. However, the presence of hard martensite also imposes restrictions on post-uniform elongation due to the strong strain localization induced in microstructures.

Structural evolution and mechanical properties of 9Cr ferritic/martensitic ODS steels developed by a direct powder forging route

ABSTRACT A nominal composition of mechanically alloyed Fe-9Cr-2W-0.2Ti-0.12C-0.35Y2O3 steel powders was consolidated via a direct powder forging route. The powder-forged samples exhibited an equiaxed grain structure with the formation of Y-Ti-O (Y2Ti2O7 or YTiO3) complex oxides and the absence of prior particle boundaries. The powder-forged samples were further heat treated, i.e. cooled at three different rates, i.e. furnace cooling, air cooling, and water quenching, followed by tempering for the air-cooled and water-quenched samples. The tensile strength at room temperature for water-quenched and normalised samples was comparable, whereas the ductility for the normalised samples was higher, while at high temperature, a good combination of strength and ductility was achieved in the tempered air-cooled samples among all the heat-treated samples. The mechanical properties achieved in the present study were at par and superior in some cases to those reported in literature. The absence of prior particle boundaries network, almost full density and equiaxed grains indicated that the powder forging route can emerge as an alternative consolidation technique to HIP and hot extrusion for the consolidation of powder metallurgy oxide dispersion strengthened steels for nuclear applications.

Study of phase evolution, mechanical, and tribological behaviour of a novel β-phase strengthened Ti-alloy with Fe and Co alloying via a laser material deposition route

A new Ti64-Fe-Co alloy was studied via a laser-material-deposition method. Associated with high growth restriction factors, β-eutectoid (Fe, Co) alloying minimizes anisotropy (due to the prior columnar β-grain growth) in the laseradditive -manufacturing (AM) built Ti-parts along with enhanced properties. Fe alloying for Ti64 via laser-AM results in superior strengthening with reduced ductility, where a good combination of strength and elongation properties can be achieved for a Ti-Fe-Co system. However, studies on Ti-Fe-Co-based systems via laser processing are limited. Co possesses a similar electronic property as Fe and the Ti-Fe system accompanies further solute addition. The effect of Co alloying the Ti64-Fe system was investigated in this study via a pre-placed laser-material-deposition method. A Ti64–5Fe-5Co alloy was formulated referring to CALPHAD simulations, along with a Ti64–10Fe composition. The new Ti-alloys were fabricated via both the laser-material-deposition and conventional vacuum arc melting routes, and the characteristics of the fabricated samples were examined. XRD analysis shows the evolution of the β-Ti phase with Fe and Co alloying, which agrees with the thermodynamic phase simulation results. The corresponding SEM micrographs depicted a β-phase dominant matrix with α-dendrites, and the solidification path was discussed. Considerable grain refinement was obtained for the laser-deposited alloys compared to the arc-melted ones, with an improved hardness value twice that of the commercial Ti64. A reduced stiffness for the laser-deposited Ti64–5Fe-5Co was observed from the load-vs-displacement characteristics, indicating matrix softening with Co alloying, which might benefit the elongation properties. The studied Ti-alloy shows a 30 % improvement in the dry-sliding wear characteristic with reduced fretting and abrasion compared to the commercial Ti64. The studied Ti-alloys were located in the theoretical d-electron space and new (Bo) ̅-(Md) ̅ vectors were introduced. Further studies on this would help in extending the applicability of laser-AM-built Ti-components.

Simultaneously improve the strength and ductility of additively manufactured Y2O3/316 L composites via optimizing heat treatment

The effect of heat treatment temperature on the microstructure and mechanical properties of Y2O3/316 L composites prepared by laser powder bed fusion was studied. The cellular substructures formed in the as-built samples remained stable when heat-treated at 1000 °C and disappeared as the temperature increased to 1100 °C. Compared with the as-built sample, a larger number of fine particles precipitated in the sample at 1000 °C, and the particles were significantly coarsened at 1100 °C. Under the stress-induced grain boundary migration mechanism, the grains undergo coarsening. The samples heat-treated at 1000 °C had the best combination of strength and ductility compared to the other samples. The high strength of the samples can be attributed to the retention of the cellular substructure and the enhancement of the Orowan strengthening mechanism. The high ductility of the sample is brought about by the formation of the twinned structure. The heat treatment developed in this work for the additive manufacturing of steel matrix composites to tailor its microstructure and mechanical properties for its various applications is critical.

The effects of forging strategies on microstructures and mechanical properties of a Ti–5Al–5Mo–5V–1Cr–1Fe near β-titanium alloy

The present study systematically investigated the influence of forging strategies on the microstructures and deformation behaviors of a Ti–5Al–5Mo–5V–1Cr–1Fe (Ti-55511) near β-titanium alloy. Microstructure analysis revealed that the as-cast alloy exhibited a basket-weave structure predominantly comprised of lamellar α phase. Three different forging methods were used to adjust the morphology of the primary α phase during the final two forging steps: 1) dual-phase (825 °C) + dual-phase forging (DD sample), 2) dual-phase + β single-phase (900 °C) forging (DS sample), and 3) β single-phase + dual-phase forging (SD sample). After standard heat treatment, the DD samples exhibited equiaxed αp due to sufficient deformation in dual-phase region, while DS samples transformed into lamellar shape due to αp reforming during the cooling process of the final β single-phase forging. In contrast, the SD samples displayed short-rod αp due to reforming in the single-phase region and insufficient deformation in the dual-phase region. All these αp and βt phases can hinder dislocation motion to enhance the strength. The DS sample exhibited the best combination of strength, ductility, and impact toughness. During tensile deformation, planar dislocation slip and {101‾1} twinning were dominant in the αp, while wave slip occurred in the βt phase. The fracture behavior transitioned from brittle to ductile after forging and heat treatment. Overall, this study offers a practical and effective method for optimizing the mechanical properties of the Ti-55511 alloy.

Precipitation Behavior and Strengthening–Toughening Mechanism of Nb Micro-Alloyed Direct-Quenched and Tempered 1000 MPa Grade High-Strength Hydropower Steel

Faced with the rapid development of large-scale pumped-storage power stations, the trade-off between the strength and toughness of hydropower steels in extreme environments has been limiting their application. The effects of Nb micro-alloying and direct quenching and tempering processes on the strengthening–toughening mechanism of 1000 MPa grade high-strength hydropower steel are studied in this paper, and the precipitation behavior of Nb is discussed. The results showed that only the 0.025Nb steel using the DQT process achieved a cryogenic impact energy of more than 100 J at −60 °C. Under the DQT process, a large number of deformation bands and dislocations were retained, refining the prior austenite grains and providing more nucleation sites for the precipitation of NbC during the cooling process. The DQT process has a more obvious local strain concentration, mainly focusing on the refined lath boundary, which indicates that the refinement of the microstructure also promotes the stacking of dislocations. The improvement in fine grain strengthening and dislocation strengthening by the DQT process jointly led to an increase in strength, resulting in a better combination of strength and toughness.

Unveiling synergistic strength and plasticity enhancement of Mg–Zn–Mn alloy via closed forging extrusion

A cost-effective, high-performance Mg-2.0Zn-1.5Mn alloy was fabricated using closed forging extrusion (CFE). The results reveal that CFE can promote a dynamic recrystallization (DRX) ratio and enhance the residual dislocation density in deformed grains and subgrains. Grain refinement is achieved through multiple DRX mechanisms, particle-stimulated nucleation, and pinning effects. In addition, the basal texture and precipitation behavior are significantly influenced by pre-forging in CFE. Finally, grain refinement and substantial residual dislocations result in a good combination of strength and plasticity, with the ultimate tensile strength of 400 MPa and elongation of 22.1%, respectively. A novel strategy for regulating the bimodal grain structure is proposed to guide the optimization of the mechanical performance of rare-earth free Mg alloys.

Achieving low hot tearing susceptibility in high-strength cast Al–Li alloys: Experimental investigation and simulation assessment

Due to the exceptional low density and high stiffness, cast Al–Li alloys are deemed suitable for structural applications. However, their economic benefits are limited by intolerable hot tearing susceptibility (HTS) during casting. This work aims to optimize alloy compositions that compromise low HTS and good mechanical properties. Six alloys (Alloys 1–6) with potentially high hot tearing resistance were selected by regulating Li, Cu and Mg additions based on the Kou's criterion and ProCAST simulation. Experimental results indicated that in contrast to Alloys 1–4, Alloys 5 & 6 containing higher solute contents show anomalously high HTS, significantly deviating from the predictions. It was further revealed that this phenomenon originates from a variety of Li-rich inclusions formed at interdendritic channels, which lead to strain localization and hinder residual liquid refilling. Then, Alloys 1–4 with low HTS were subjected to a tailored subsequent heat treatment to achieve optimal mechanical properties. Among the tested alloys, Alloys 3 & 4 exhibit comparatively lower ductility attributed to strain accumulation at the interface between coalesced Sʹ-Al2CuMg phases and Al matrix. In comparison, a good combination of strength and ductility (YS = 371 ± 14 MPa, UTS = 456 ± 19 MPa, EL = 2.5 ± 0.1 %) was successfully achieved in Al-2.5Li–2Cu–1Mg-0.15Zr alloy (Alloy 2) due to the synergistic reinforcement of δʹ-Al3Li and T1-Al2CuLi precipitates. Compared to other available cast Al–Li alloys, Alloy 2 possesses better hot tearing resistance while being highly competitive in strength. Our results are anticipated to contribute scientific guidance for developing high-performance cast Al–Li alloys with low HTS.

Properties of a Pressureless Sintered 2Y-TZP Material Combining High Strength and Toughness

Yttria stabilized zirconia materials are frequently used in mechanical engineering and biomedical applications. Demanding loading conditions require materials combining a high level of strength and fracture toughness. A ready-to-press alumina doped 2 mol% yttria-stabilized zirconia powder was shaped by axial pressing and sintering in air at 1250–1500 °C for 2 h. At 1350 °C the best combination of strength (1450 MPa) and toughness (7.8 MPa√m) was achieved. Materials sintered in the middle of the chosen temperature range combine full density, high transformability and small grain size. Toughness measurements by direct crack length measurements delivered unrealistically high fracture toughness values.

Reorientation induced plasticity in full αʺ martensite Ti-9V-1Fe-4Al alloy

The microstructure and deformation mechanism of a full orthorhombic αʺ martensite Ti-9V-1Fe-4Al (wt.%) alloy were investigated by XRD, TEM, EBSD analyses and tensile tests. The results show that the quenched alloy has a twinned-martensite microstructure and {111}αʺ type I internal twins are formed as the lattice invariant shear for martensite transformation. The alloy plastically deforms by a complex reorientation of αʺ martensite variants via the movement of the inter-variant boundaries of <211>α′′ type Ⅱ twin, and deformation twinning of {111}α′′ type I internal twin and of newly generated {011}αʺ compound twin in primary twinned martensites. {130}α′′<3¯ 10>α′′ and {110}α′′<1 1‾ 0>α′′ plastic twins were not observed in the alloy. Such a kind of deformation induced martensite reorientation results in a good combination of strength and plasticity with yielding strength of 480 MPa, tensile strength of 1030 MPa and elongation of 23% in the alloy. The calculated results further show that the shears of {111}α′′ type I, <211>α′′ type II and {011}α′′ compound twins and the shuffle of {111}α′′ type I twin increase, while the shears of {130}α′′<3‾ 10>α′′ and {110}α′′<1 1‾ 0>α′′ twins and the shuffle of {130}α′′<3‾ 10>α′′ twin decrease with an increase of the lattice parameter ratio bα′′/aα′′. The shears of these activated twinning systems are larger than those of {130}α′′<3‾ 10>α′′ and {110}α′′<1 1‾ 0>α′′ twins, and the shuffle of {111}α′′ type I twin is also bigger than that of {130}α′′<3‾ 10>α′′ twin in the present alloy, which implies that the operative twining modes cannot be derived simply in terms of the shear and shuffle magnitude in full αʺ martensite Ti based alloys.

Bimodal grain structure and balanced mechanical properties of cryo-rolled Mg-Zn-Y alloy via twinning-induced recrystallization

The microstructure and mechanical properties of the hot-rolled and cryo-rolled Mg-2Zn-0.85Y (wt.%) alloys before and after annealing were studied comparatively. The results show that the cryo-rolled alloy after annealing exhibits a strength and plasticity product of up to 6885 MPa·%, which is the highest among these alloys. The good combination of strength and ductility is mainly attributed to the bimodal grain structure with a weakened texture. Recrystallization primarily occurs in grains with <112¯0>/30.1° twinning, but not in the grains without <112¯0>/30.1° twinning, resulting in the formation of the bimodal structure. The cryo-rolling process could become a promising method for regulating the microstructure and properties of magnesium alloys.

Effect of Two-Step Solution Treatments on the Microstructure and Mechanical Properties of B357 Aluminum Alloy

AbstractThis study investigates the effect of two-step solution treatments and aging times on the microstructure and mechanical properties of B357 Al–Si alloy, part of the most widely used cast aluminum alloy. Three sets of artificial aging heat treatments were conducted on the tensile samples prepared from B357 alloy produced by low-pressure die casting. Firstly, the conventional artificial aging heat treatment (T6) was carried out by solutionizing the tensile samples at 543 °C for 8.5 h, water quenching at 60 °C, and then artificially aging for 8.5 h at 160 °C. In the two-step solution treatment, the samples were solutionized at 400, 440, 480, and 520 °C for 4 h and then solutionized at 543 °C for 8.5 h and water quenched to 60 °C and then artificially aged for 8.5 h at 160 °C. Thirdly, the samples were solutionized at 480 °C for 4 h, solutionized at 543 °C for 8.5 h, water quenched to 60 °C, and artificially aged for 3–192 h. Despite different solutioning and aging processes, no significant differences were observed in the microstructures of the samples. Si particle coarsening was observed with increasing solution temperature (400–520 °C) and aging times (3–192 h). Si-containing dispersoids and dispersoid-free zones (DFZ) were observed in the primary-α matrix. While DFZ width increased with temperature and aging, dispersoid zones in primary-α dendrites significantly decreased. Differential Scanning Calorimetry (DSC) analysis shows that two-step solution treatment in B357 alloy increases β′ precipitates for Mg2Si precipitation strengthening. The two-step solutionized and aged sample showed the best combination of strength and ductility among all aged samples. B357 alloy exhibited the highest yield and tensile strength (309.7, 366.1 MPa) with 6% elongation for two-step solutionizing and 48 h aging. All aged B357 alloys showed ductile fracture as the primary fracture mode. However, brittle fractured Si particles were observed on the fracture surfaces.

Enhancing the Tensile Properties and Ductile-Brittle Transition Behavior of the EN S355 Grade Rolled Steel via Cost-Saving Processing Routes.

Structural rolled steels are the primary products of modern ferrous metallurgy. Consequently, enhancing the mechanical properties of rolled steel using energy-saving processing routes without furnace heating for additional heat treatment is advisable. This study compared the effect on the mechanical properties of structural steel for different processing routes, like conventional hot rolling, normalizing rolling, thermo-mechanically controlled processing (TMCP), and TMCP with accelerating cooling (AC) to 550 °C or 460 °C. The material studied was a 20 mm-thick sheet of S355N grade (EN 10025) made of low-carbon (V+Nb+Al)-micro-alloyed steel. The research methodology included standard mechanical testing and microstructure characterization using optical microscopy, scanning and transmission electronic microscopies, energy dispersive X-ray spectrometry, and X-ray diffraction. It was found that using different processing routes could increase the mechanical properties of the steel sheets from S355N to S550QL1 grade without additional heat treatment costs. TMCP followed by AC to 550 °C ensured the best combination of strength and cold-temperature resistance due to formation of a quasi-polygonal/acicular ferrite structure with minor fractions of dispersed pearlite and martensite/austenite islands. The contribution of different structural factors to the yield tensile strength and ductile-brittle transition temperature of steel was analyzed using theoretical calculations. The calculated results complied well with the experimental data. The effectiveness of the cost-saving processing routes which may bring definite economic benefits is concluded.

Enhanced strength-ductility combination in the aluminum-gold system by heterogeneous distribution of nanoparticles via ultra-severe plastic deformation and reactive interdiffusion

Ultrafine-grained aluminum alloys are of interest due to their high strength-to-weight ratio, but they usually suffer from poor uniform ductility. In this study, an Al-Au alloy with a good combination of strength and ductility is produced by the heterogeneous distribution of Al2Au nanoparticles in an aluminum matrix. To generate such heterogeneity, the alloy is synthesized by ultra-severe plastic deformation of aluminum and gold powders via the high-pressure torsion (HPT) method. Reactive interdiffusion occurs during the process leading to the heterogeneous formation of intermetallic particles and a good strength-ductility synergy (200 MPa yield stress and 15% uniform elongation). Nanoparticles gradually distribute within the matrix and once a uniform nanoparticle distribution is achieved, the alloy shows no further increase in strength, but it completely loses its ductility. It is concluded that not only the presence of nanoparticles but more importantly the heterogeneity of their distribution can positively influence the strength-ductility combination in ultrafine-grained aluminum alloys. The findings of this study suggest that future studies on heterogeneous precipitation hardening can be a solution to achieve ductile precipitation-hardened alloys.

Nanocrystalline Ti‐Al‐Mo‐Zr‐Si Alloy (TC11) by Laser Powder Bed Fusion In‐situ Alloying

TC11 alloy is an important high temperate Ti alloy. Its laser in‐situ alloying by powder bed fusion‐laser beam (PBF‐LB) has been explored in this study. Results show that it is feasible to print the TC11 alloy using elemental powders rather than pre‐alloyed powder, in terms of high density and good combination of strength and ductility at both room and elevated temperatures, along with minor loss of composing elements. Interestingly, it is noticed that an unusual nanocrystalline microstructure has formed due to the use of ZrH2 powder feedstock, partially explaining the reason for the good mechanical properties achieved. Finite element analysis has been employed to understand the in‐situ alloying. Furthermore, a post processing by micro‐arc oxidation (MAO) has been employed to the alloy, aiming to enhance its high‐temperature oxidation resistance. The results make an implication that hydrides such as ZrH2 may hold the promise to develop nanosized, advanced Ti materials through laser in‐situ alloying, and MAO can be considered for PBF‐LB prepared TC11 alloy.

Toward high strength and large strain hardening Zn alloys via a novel multiscale-heterostructure strategy

Zn alloy has attracted much attention as a biodegradable material for biomedical applications. However, due to the significant strain softening of Zn alloys, how to break the bottleneck of synergistic yield strength and uniform elongation is an urgent problem to be solved. In this work, a Zn-2.3Cu-0.8Mn (wt.%) alloy was fabricated via low-temperature extrusion and annealing at 330 °C for 1 h to attain dual heterostructures with bimodal grains and multi-scale second phases, focusing on the effect of heterostructure on the mechanical properties. Uniaxial tensile test and loading-unloading-reloading test were applied to reveal the mechanical properties of the Zn-2.3Cu-0.8Mn alloy, while scanning electron microscope, electron backscatter diffraction, and transmission electron microscope were used to characterize its microstructure. Compared with the as-extruded alloy with uniform and fine grains, 330–1 alloy achieves a better combination of strength and uniform elongation (yield strength: 287.8 ± 8.5 MPa, ultimate tensile strength: 321.4 ± 6.8 MPa, and uniform elongation: 14.2 ± 1.8%). The high strength was primarily attributed to the coordination of grain boundary strengthening, hetero-deformation induced strengthening, Orowan strengthening, and dislocation strengthening. Besides, the coarse grains, twinning, as well as the suppression of grain boundary sliding and phase boundary sliding promoted dislocation proliferation and storage capacity, thereby improving work hardening capacity. The large strain hardening capacity was responsible for excellent plasticity. This study provides a feasible strategy for the design of Zn-based alloys with an excellent combination of high strength and strain hardening capacity.