Electron Backscatter Diffraction Analysis Research Articles

Microstructural Evolution and Phase Transformation on Sn–Ag Solder Alloys under High‐Temperature Conditions Focusing on Ag3Sn Phase

This study investigates the microstructural and phase transformations in Sn–Ag solder alloys under high‐temperature conditions, utilizing X‐ray diffraction, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) analyses. Analytical techniques are employed pre‐ and postcontrolled thermal cycling from 30 to 180 °C, aimed at emulating solder reflow processes. The analysis at room temperature demonstrates pronounced crystalline peaks, suggesting a preferred orientation within the crystal structure. Upon heating, peak broadening suggests grain growth and the onset of recrystallization. SEM and energy‐dispersive spectroscopy analyses corroborate these findings, displaying a fine‐grained, well‐distributed microstructure with a homogenous composition of Sn and Ag elements. EBSD provides insights into the orientation and texture of grains, revealing a weak‐to‐moderate texture across the phases. Postexperiment data indicate a dominant presence of larger grains and significant variation in grain size, with an area‐weighted mean grain size of 68.47 μm and a standard deviation of 8.68 μm; this suggests significant grain growth and coarsening of the Ag3Sn intermetallic compounds. These structural evolutions have crucial implications for the mechanical properties and reliability of the solder alloy in electronic assemblies, underscoring the need for further exploration of lead‐free solder materials in the electronics industry.

Igneous intrusion origin for the petrofabric of Erg Chech 002

AbstractAchondrites provide an opportunity to examine the igneous processes of differentiated bodies in our solar system. The recent discovery of several silica‐rich achondrites suggests that andesitic crusts were more common among planetesimals than previously thought, though the processes behind their emplacement are not well understood. Here, electron backscatter diffraction (EBSD) is used to investigate the igneous emplacement conditions of Erg Chech 002 (EC 002), a recently discovered ungrouped achondrite representing andesitic magmatism ~2 Myr after the formation of calcium–aluminum‐rich inclusions (CAIs). EBSD analyses of crystallographic preferred orientations (CPOs) for augite and plagioclase feldspar phenocrysts indicate that EC 002 exhibits a weak foliation CPO. Augite misorientation inverse pole figures (mIPF) indicate preferential slip along the (100)[001] system with a distinct shift toward the {0kl}[u0w] system in plastically deformed grains. Our findings support the hypothesis that EC 002 was likely emplaced in the lower regions of a magmatic intrusion. Augite slip signatures suggest that EC 002 crystallization and emplacement were restricted to high temperatures (>800°C) and experienced at least two strain regimes. The distinct shift from a dominant (100)[001] slip system, which corresponds to high temperatures (800–1050°C), to a [0kl][u0w] slip system indicates an increased strain rate due to shock deformation (1–5 GPa) attributed to ejection by hypervelocity impact.

Microstructure evolution and local mechanical properties of friction stir additively manufactured (FSAM) AA5083/AA6061/AA7075 gradient composite.

The current study is focused on the successful fabrication and characterization of microstructure and properties gradient composite made of 3 mm thick sheets of AA5083-O, AA6061-T6, and AA7075-T6 alloys using friction stir additive manufacturing (FSAM) technique. Two combinations of four layered FSAM builds (6756 and 7567) were fabricated successfully without any major defects at the optimized process parameters of 850 rpm (tool rotational speed) and 55 mm/min (tool transverse speed). The material mixing, interfacial bonding features, microstructure evolution, and mechanical performance within the stir zones (SZ) were thoroughly examined using advanced characterization techniques. Electron backscatter diffraction (EBSD) analysis confirmed a gradient microstructure along the build depth in both FSAM builds, with average grain sizes decreasing from 52 μm (AA5083), 46 μm (AA6061), and 40 μm (AA7075) in base metals to ∼ 4 to 7 μm within the SZ. The remarkable grain refinement within the SZ was mainly attributed to the dominant presence of the continuous dynamic recrystallization (CDRX) mechanism. Texture analysis corresponding to pole figures (PFs) and orientation distribution function (ODF) plots reveals the crystallographic texture evolution along the build depth. The prevalent existence of B/ and C textures throughout all regions of the FSAM builds affirms the presence of ample shear strain during the FSAM procedure. Through thickness miniature tensile and microhardness tests depict the gradient in mechanical performance for both the FSAM builds along the build depth. Microhardness gradients in the range from 80 HV0.1 to 145 HV0.1 were observed along the build depth. The axial sample in the build direction shows appreciable strength (265 MPa and 224 MPa) and uniform elongation (28% and 24 %) for 6756 and 7567 FSAM build, respectively. Furthermore, remarkable strain hardening behaviour corresponding to hardening capacity (Hc) and hardening exponent (n) was noticed for both the axial build samples compared to AA6061-T6 and AA7075-T6 base metals. These findings underscore the potential of FSAM in fabricating functionally gradient composite materials tailored to specific functional requirements.

A critical investigation of the anisotropic behavior in the WAAM-fabricated structure

PurposeWire-arc-based additive manufacturing (WAAM) is a promising technology for the efficient and economical fabrication of medium-large components. However, the anisotropic behavior of the multilayered WAAM-fabricated components remains a challenging problem.Design/methodology/approachThe purpose of this paper is to conduct a comprehensive study of the grain morphology, crystallographic orientation and texture in three regions of the WAAM printed component. Furthermore, the interdependence of the grain morphology in different regions of the fabricated component with their mechanical and tribological properties was established.FindingsThe electron back-scattered diffraction analysis of the top and bottom regions revealed fine recrystallized grains, whereas the middle regions acquired columnar grains with an average size of approximately 8.980 µm. The analysis revealed a higher misorientation angle and an intense crystallographic texture in the upper and lower regions. The investigations found a higher microhardness value of 168.93 ± 1.71 HV with superior wear resistance in the bottom region. The quantitative evaluation of the residual stress detected higher compressive stress in the upper regions. Evidence for comparable ultimate tensile strength and greater elongation (%) compared to its wrought counterpart has been observed.Originality/valueThe study found a good correlation between the grain morphology in different regions of the WAAM-fabricated component and their mechanical and wear properties. The Hall–Petch relationship also established good agreement between the grain morphology and tensile test results. Improved ductility compared to its wrought counterpart was observed. The anisotropy exists with improved mechanical properties along the longitudinal direction. Moreover, cylindrical components have superior tribological properties compared with cuboidal components.

Dynamic tensile behavior and constitutive model of a novel high-strength and high-toughness plate steel

The dynamic tensile behavior of a novel-developed plate steel with high strength and toughness is investigated. Uniaxial tensile tests are conducted at various strain rates varying from 0.1 s−1 to 1000 s−1, and then scanning electron microscope and electron backscattered diffraction analyses are performed on tensile specimens at failure. A large and homogeneous deformation is demonstrated during the tension and small necking is observed at failure; all test results reveal the strain rate dependency of this novel plate steel: with an increase in strain rate, the yield strength, ultimate tensile strength, and total elongation increase, whereas the uniform elongation decreases. Microstructure analyses find dimple fracture surface and considerable deformation twins and dislocations, confirming the high strength and high ductility of the novel plate steel. The density of twins and dislocations demonstrates a positive correlation with the increasing strain rate, aligning with the variations observed in the mechanical properties. Engineering stress–strain curves exhibit a necking lag effect at high strain rates, and this effect is considered when solving the true stress–strain relationships by a developed hybrid experimental–numerical method. A modified Johnson-Cook model considering the power law strain rate effect and thermal softening effect caused by adiabatic temperature rise is finally proposed and verified. This work explores the dynamic mechanical behavior of the novel plate steel at different strain rates, promoting its application in aseismic design and impact resistance engineering.

Effect of Al7075 and activated carbon reinforced composite on optimizing WEDM responses

This paper presents wire cut electrical discharge machining (WEDM) response characteristics of Aluminium 7075 (Al7075) reinforced with powdered activated carbon (PAC) composite. In recent days WEDM has become a significant machining process in targeting its benefits of contributing improved material removal rate (MRR) and low surface roughness (SR). This is due the rising need for intricate, accurate, and superior structural components, the WEDM process emerges as a formidable alternative to traditional machine tools. In this work Pulse-on time (Ton), pulse-off time (Toff), discharge current (IA) and servo speed rate (SS) are the variables to be given as input and machining responses such as MRR and SR are studied. From Analysis of Variance (ANOVA) study it is found that discharge current and servo speed is the significant parameters. The optimal desirability condition is obtained with input parameters Ip: 2000 mA; Ton: 8.9 μs; Toff: 25 μs and SS: 150 rpm for the precision machining. The optimum response parameters are found as MRR 10.46 mm3/min and SR 3.32 μm. Results shows that the model designed for the prediction of MRR produces an above 98.27% and the prediction of SR is above 97.17%. The error percentage among the experimental and predicted MRR and SR were estimated. Additionally confirmatory test is performed with optimal results achieved from response surface methodology (RSM) and desirability technique. Metallurgical tests like electron backscatter diffraction analysis (EBSD) and microstructure are conducted to confirm the surface properties and atomic force morphology (AFM) analysis is applied to clarify the structural features of machined composites. The results revealed that the variation of hard deflection is caused by depression of eroded materials on the top layers of machined surface.

Effect of heat treatment on hydrogen embrittlement susceptibility of Al0.25CoCrFeNi high entropy alloy

In this study, the influences of annealing and aging treatments on the hydrogen embrittlement (HE) behavior of the cryo-rolled Al0.25CoCrFeNi high entropy alloy (HEA) were investigated through tensile tests and electrochemical hydrogen charging experiments. The results found that the aged sample showed high strength but was more susceptible to HE. A trade-off between the strength and HE resistance was achieved in the annealed + aged sample. Electron backscatter diffraction analysis and fracture characteristics were performed to clarify the HE mechanism. The high dislocation density and aggregated second phase along the grain boundaries in the aged sample were the important factors to help the initiation of HE crack, and then increasing the HE susceptibility. The annealed + aged sample with low dislocation density and aging precipitation reduced the risk of hydrogen-induced cracking and resulting in the excellent HE resistance. This work offered the method to obtain a comprehensive improvement in the strength and HE resistance of this alloy.

Effect of initial grain size on hot deformation behavior and recrystallization mechanism of Al-Zn-Mg-Cu alloy

Grain size is industrially important for improving mechanical properties and formability. In order to investigate the effect of grain size on the hot workability and deformation mechanisms, Al-Zn-Mg-Cu alloys with different initial grain sizes, 241.2, 100.4 and 48.4 μm, were subjected to hot compression tests. Using the established constitutive equation, the rheological behavior is described and the influence of the initial grain on the thermal deformation behavior is analyzed. Electron back-scatter diffraction (EBSD) analysis was used to study the dynamic recrystallization (DRX) mechanisms of Al-Zn-Mg-Cu alloys with different initial grain sizes. The microstructures obtained under various deformation conditions were analyzed. The results show that decreasing the initial grain size enhances both the peak stress and the activation energy for thermal deformation. Meanwhile, the dynamic recrystallization mechanism varies depending on the initial grain size. Continuous dynamic recrystallization (CDRX) is the primary DRX nucleation mode for coarse-grained alloys. Nonetheless, discontinuous dynamic recrystallization (DDRX) is predominant for alloys with fine grains.

Interplay of Heat Treatment and Deformation Temperature on the Microstructural Evolution and Mechanical Behavior of SLM AlSi10Mg Alloy

This study conducts a comprehensive examination of the microstructural and dislocation dynamics of AlSi10Mg alloys under various thermal conditions, utilizing quasi in-situ Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM) analyses. The research focuses on comparing the microstructural response of as-built and T6 heat-treated samples to mechanical stress at both ambient (298K) and cryogenic (77K) temperatures. EBSD analysis underscores the grain stability under applied strain, while TEM investigations expose notable variations in dislocation mobility influenced by temperature, with a particular emphasis on the interaction between dislocations and silicon particles at cryogenic temperatures. An observed increase in Geometrically Necessary Dislocation (GND) density at 77K points to enhanced resistance to plastic deformation, suggesting mechanisms of cryogenic strengthening. The findings illuminate the impact of heat treatment in augmenting the mechanical properties of the alloy, shedding light on its potential applications in aerospace and cryogenic environments.

Developing a novel Mg[sbnd]2Zn[sbnd]3Li[sbnd]1Gd alloy sheet with high room-temperature formability by introducing an elliptical texture distribution

In recent years, modification of texture distribution has been considered a valid approach to improve the room-temperature (RT) formability of magnesium (Mg) alloys. In this study, a novel Mg2Zn3Li1Gd alloy sheet with weak elliptical-texture was fabricated by cold rolling and subsequent annealing, and it showed an excellent Erichsen (IE) value near 7.1 mm. Both quasi-in-situ electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analysis indicate that considerable basal and pyramidal dislocations can be activated in the cold rolling process. During annealing, these dislocations can induce nucleation and then cause preferential misorientation relationships around 〈uvt0〉 concerning the nuclei and parent grains, which can facilitate the formation of elliptical texture. Furthermore, the particle-stimulated nucleation (PSN) mechanism and the co-segregation of Zn and Gd at grain boundaries (GB) further weak texture intensity. Finally, the mechanical properties of the Mg2Zn3Li1Gd alloy sheet are significantly improved.

Investigation on microstructural and mechanical integrity of GTAW dissimilar welded joint of IN 718/ASS 304L using Ni-based filler IN 625 using EBSD and DHD techniques

The current study investigates the relationship between the microstructural and structural characteristics of dissimilar gas tungsten arc welding (GTAW) between Inconel 718 (IN 718) and austenitic stainless steel 304L (ASS 304L) using Inconel 625 (IN 625) as a filler material. The microstructural characterization of the dissimilar weld includes the application of an optical microscope (OM), field emission scanning electron microscopy (FE-SEM) including energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). The optical and FESEM analysis of the base metals (BM) indicates the austenitic nature of the IN 718 BM matrix, which incorporates strengthening precipitates γ' and γ'' distributed throughout the Nickel matrix. In contrast, the ASS 304L BM exhibits an austenitic microstructure along with twins. Moreover, IN 625 weld metal exhibits austenitic microstructure in the form of cellular, columnar, and equiaxed dendrites. Elemental segregation demonstrates the existence of Nb, and Mo-rich carbides, including the laves phases at the interdendritic regions of the IN 625 weld zone and IN 718 Heat-Affected Zone (HAZ). Ferrite stringers were noticed in the HAZ of ASS 304L. EBSD analysis shows the improved texture of the weld zone exhibiting fine equiaxed recrystallized microstructures. EBSD/Kernel average misorientation (KAM) micrographs reveal the existence of high strain at the weld metal grain boundaries. Vickers microhardness assessment of the dissimilar weld demonstrates the high hardness of 257.5 HV for the IN 625 weld zone because of the occurred NbC, laves phases, and Mo-rich carbides. Room temperature tensile characterization shows the failure of tensile specimens from ASS 304L BM reflecting the high strength of the IN 625 weld metal (662 MPa). Tensile tests at high temperatures were performed at 550º C, 600º C, and 650º C. High-temperature tensile result exhibits a higher tensile strength of IN 625 weld zone than the ASS 304L BM, as the tensile specimens fails from 304L BM. The specimen exposed at 550º C exhibits the highest tensile strength of 388 MPa. The Charpy impact toughness test was conducted, with notches at the HAZ of ASS 304L, HAZ of IN 718, and the weld center being evaluated. The toughness value of the weld metal decreases (99 J) due to occurrence of the secondary precipitates. To analyze residual stress, the deep hole drilling (DHD) technique was used, which revealed that the peak residual stress (230 MPa) is induced at 6 mm from the weld surface and falls into the tensile stress category.

Effect of multifunction cavitation on microstructure and plane bending fatigue properties of low-alloy steel

Multifunction cavitation (MFC) has potential as an environmentally friendly surface-modification method. In the present study, the modified surface layer and the fatigue properties for MFC-processed low-alloy steel were investigated. When the processing time was longer than 2 min, the surface roughness increased and the surface potential decreased. The maximum compressive residual stress was induced after a processing time of 2 min, and decreased for longer processing times. Electron backscatter diffraction analysis of a cross section of a sample subjected to MFC for 30 min showed that the modified layer was thicker than that for samples processed for shorter times. The fatigue life at high cycle numbers increased for the specimens processed by MFC under the conditions corresponding to the greatest compressive residual stress. MFC processing was shown to be effective in improving the fatigue properties of steel, and therefore has potential as a next-generation surface-modification method.

Dependence of mechanical properties on the phase composition of intercritically annealed medium-Mn steel as the main competitor of high-strength DP steels

Depending on the alloy composition, intercritical annealing may provide different phases in the microstructure. For low-alloyed dual-phase (DP) steels it is usually ferrite and martensite, while for medium-Mn steels retained austenite is also formed. In a present study, a wide intercritical temperature range was applied to a 5% Mn steel to investigate possible microstructure combinations: ranging from fully ferritic, through ferritic-austenitic, multiphase, to fully martensitic, which were next investigated in terms of mechanical properties to clarify the behavior of this type of material. The obtained results together with technological issues and economic indicators were next compared to mechanical properties of typical DP steels in order to assess the possibility of replacing this material in car production. The mechanical properties were evaluated using static tensile and hardness tests. The phase composition was determined qualitatively and quantitatively using dilatometry, X-ray diffraction measurements, and electron backscatter diffraction analysis. The results suggest that both initial austenite and martensite fractions have a decisive influence on the yielding and elongation of steel; however, the tensile strength depends mainly on the sum of martensite initially present in the microstructure and the strain-induced martensite formed from the plastically deformed austenite regardless of the initial retained austenite—martensite ratio. The results indicate superior total elongation of medium-Mn steels reaching 30% compared to DP steels with a similar strength level in the range between 900 and 1400 MPa. However, medium-Mn steels could be a significant competitor to dual phase steels only if some technological problems like discontinuous yielding and serrations are significantly reduced.

Preparation of Binary and Ternary Laves and µ-Phases in the Ta–Fe(–Al) System for Property Analysis at the Microscale

AbstractTopologically close-packed (TCP) intermetallic phases are attractive candidates for adapting the property profile of both structural and functional materials, but their mechanical behavior, in particular below their brittle-to-ductile transition, is generally still poorly understood. The systematic analysis of the underlying deformation mechanisms requires the fabrication of homogeneous samples with sufficiently high purity and large enough grain size. Here, we describe identified pathways on the example of Laves and µ-phases from the binary Ta–Fe and ternary Ta–Fe–Al systems with regard to input materials, liquid metallurgy synthesis, heat treatment, and metallographic preparation methods. Preparation routes for structural analysis by electron backscatter diffraction and mechanical analysis by nanomechanical testing, as well as the transferability of our approach to other alloy systems containing TCP phases, are outlined and discussed.

Evolution of microstructure and mechanical properties of aluminum matrix composites reinforced with dual-phase heterostructures

The trade-off between strength and plasticity has long been challenging in particle-reinforced aluminum matrix composites (PRAMCs). This study proposes an innovative approach for preparing aluminum matrix composites (AMCs) using a dual-phase hybrid of FeCoNiCrMn high entropy alloy (HEA) and multiscale aluminum oxide (Al2O3) particles. The microstructure evolution and strengthening mechanisms were evaluated through scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The results demonstrated that the dual-phase particle strengthening resulted from the alternating distribution and synergistic action of HEA and Al2O3 particles within the matrix, forming a continuous strain buffer with a strength gradient. Notably, introducing HEA and nano-Al2O3 led to a higher density of dislocations. Additionally, EBSD analysis revealed a uniform strain distribution within the AMCs, with a significant concentration of kernel average misorientation (KAM) near the grain boundaries (GBs). In terms of micromechanical properties, the micro-zones of heterogeneous phases exhibit exceptionally high elastic modulus and nanohardness. In terms of macroscopic mechanical properties, the material exhibited impressive ultimate compressive strength and compression ratio values of 447.9 MPa and 37.9 %, respectively. These results represented a remarkable enhancement of 72.1 % and 6.6 % compared to the single FeCoNiCrMn HEA strengthening. Moreover, when applying the HEA + nano-Al2O3 blending mode, the ultimate compressive strength further increased to 506.7 MPa, representing an astonishing boost of 94.7 %. This significant strength improvement can be attributed to effective interfacial bonding, grain refinement, and a high dislocation density resulting from both HEA and Al2O3 particles.

Temperature evolution, IMC formation, and resulting bonding efficacy in bimetallic tubular components fabricated by a novel friction stir backward extrusion cladding method

The ability to economically offer distinct properties within a single component has gathered significant attention for bimetallic or cladded tubular components across various industries. A novel friction stir-based cladding method and its in-depth analyses to achieve internal cladding of Al inside the stainless steel (SS) tubes are presented. The process outcome with the variation in process parameters and its impact on heat generation and intermetallic compounds (IMCs) formation was analyzed. In this process, the joining between the base substrate and the cladded material is due to the heat generation that leads to interdiffusion and ultimately promotes the formation of IMCs. The mechanism of IMCs formation, its growth phenomenon, and its impact on joining efficacy were investigated. The cladded Al exhibited an approximately twofold increase in grain size compared to the base Al alloy, as revealed through electron back-scattered diffraction (EBSD) analysis. The coarser grains help to restrict the propagation of fracture during the flattening test. The cladded tube exhibits no sign of delamination after compression, which paves the way for the industrial adoption of the process.

Delineating the Ultra-Low Misorientation between the Dislocation Cellular Structures in Additively Manufactured 316L Stainless Steel.

Sub-micro dislocation cellular structures formed during rapid solidification break the strength-ductility trade-off in laser powder bed fusion (LPBF)-processed 316L stainless steel through high-density dislocations and segregated elements or precipitates at the cellular boundaries. The high-density dislocation entangled at the cellular boundary accommodates solidification strains among the cellular structures and cooling stresses through elastoplastic deformation. Columnar grains with cellular structures typically form along the direction of thermal flux. However, the ultra-low misorientations between the adjacent cellular structures and their interactions with the cellular boundary formation remain unclear. In this study, we revealed the ultra-low misorientations between the cellular structures in LPBF-processed 316L stainless steel using conventional electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD), and transmission electron microscopy (TEM). The conventional EBSD and TKD analysis results could provide misorientation angles smaller than 2°, while the resolution mainly depends on the specimen quality and scanning step size, and so on. A TEM technique with higher spatial resolution provides accurate information between adjacent dislocation cells with misorientation angles smaller than 1°. This study presents evidence that the TEM method is the better and more precise analytical method for the misorientation measurement of the cellular structures and provides insights into measuring the small misorientation angles between adjacent dislocation cells and nanograins in nanostructured metals and alloys with ultrafine-grained microstructures.

Effects of Hot rolling Reduction on Microstructural Evolution and Mechanical Properties of 1.25Cr-1Mo-0.5V-0.3C Steel for High-Speed Rail Brake Discs

In this study, the effect of rolling of 1.25Cr-1Mo-0.5V-0.3C American Iron and Steel Institute 4340 modified steel for highspeed railway brake discs on the microstructure and mechanical properties was investigated. The materials were hot-rolled at 0%, 51%, and 66% reduction ratios, and then analyzed by optical microscopy, scanning electron microscopy, and electron backscattering diffraction (EBSD). needle-shaped ferrite block morphology in bainite varied with the rolling ratio. EBSD analysis reveals dynamic recovery and dynamic recrystallization, affected ferrite block boundaries and dislocation densities during rolling. Mechanical tests showed that hardness, toughness and elongation increase at higher rolling reduction ratio, while strength remained relatively constant. In particular, the impact toughness increased almost twice from the level of 70 J in S1 (0% reduction) to the level of 130 J in S3 (66% reduction). These results showed that the hot rolling can significantly improve the strength and toughness combination of cast brake discs material.

Mechanical Alloying Synthesis and Spark Plasma Sintering Consolidation of Al-Ti-Si-W Alloys

Al-Ti-Si-W quaternary powders were mechanically synthesized by planetary ball milling; and further consolidated by spark plasma sintering. The nominal compositions of the quaternary alloys were designed to be Al60Ti30Si5W5 and Al45Ti40Si10W5 (wt.%). The microstructural evolution of intermetallic compounds in Al-Ti-Si-W alloys included titanium aluminide, titanium silicide, and ternary alloys (AlxTiy, TixSiy, and TixAly,Siz), whereas W was embedded in the Al-Ti matrix as a single phase. The phase composition and grain size distribution were investigated using electron backscatter diffraction analysis, in which refined and uniform microstructures (less than 0.3 μm) were attributed to severe plastic deformation and rapid densification of the pre-alloyed powders. The mechanical properties were correlated with the Al content in the quaternary alloys; a high hardness of 1014.6 ±73.5 kg/mm2 was observed.

Grain-selective growth makes Al0.1CoCrFeNi high entropy alloys strong and ultra-ductile

The trade-off between strength and ductility of structural materials has always been a concern, and the pursuit of higher strength often comes with the inevitable sacrifice of ductility, which poses challenges for the design and manufacture of high-performance engineering materials. In this study, we introduce a novel concept called grain-selective growth (GSG) to address the strength-ductility trade-off by effectively triggering the strain hardening capacity of the single-phase FCC HEAs. Specifically, we prepared an Al0.1CoCrFeNi high-entropy alloy with a heterogeneous grain structure using cyclic rolling and annealing. By employing this approach, our GSG HEA achieves an ultra-ductility with ∼53% uniform elongation and an ultimate tensile strength of 1165 MPa. Rapidly accumulating geometrically necessary dislocations in the domain boundary region, as revealed through electron backscatter diffraction analysis, have led to the development of high-level heterogeneous deformation-induced (HDI) stress. In addition, we also observed synergistic strain hardening effects generated by various deformation mechanisms, such as dislocation pile-ups, stacking faults (SFs), deformation twinning, dislocation walls, and SF networks. This study provides valuable insights for the manufacturing of high-performance heterostructure materials, making it possible to develop advanced alloys with higher strength and ductility, suitable for a wide range of engineering applications.