Mechanical Twinning Research Articles

Creep behavior and creep-oxidation interaction of selective electron beam melted Ti–48Al–2Cr–2Nb alloy at different temperatures

In this work, creep behavior and creep-oxidation interaction behavior of Ti–48Al–2Cr–2Nb alloy fabricated by selective electron beam melting at different temperatures were investigated in detail. This alloy exhibits a near-γ microstructure composed of coarse/fine mixed equiaxed grains. Creep test results show that creep behavior of this alloy is sensitive to temperature. This is mainly manifested in that creep life reduces significantly by 84.8 % as temperature increases from 800 °C to 850 °C. During creep, discontinuous dynamic recrystallization characterized by grain nucleation and growth and continuous dynamic recrystallization characterized by strain gradient and orientation accumulation occur simultaneously. The formation of mechanical twins plays an important role in stimulating dynamic recrystallization. Meanwhile, creep deformation and fracture mechanisms of this alloy at different temperatures were also discussed. On the other hand, oxidation test results reveal that the applied tensile stress has a positive effect on the oxidation behavior of this alloy: the growth of TiO2 oxide is inhibited and the oxidation rate is slowed down. However, under creep-oxidation interaction, the intergranular cracking of the oxide film occurs along with the necking of the alloy matrix during creep.

Microstructural studies of CuCrFeNi2Mn0.5 high entropy alloy during cold rolling

A study was conducted to determine the impact of cold rolling on the evolution of the microstructure of the CuCrFeNi2Mn0.5 high entropy alloy. Cold rolling resulted in the development of crystallographic textures and microstructure evolution. It was observed that the main deformation mechanism during cold rolling of the mentioned alloy is the movement of dislocations and the formation of mechanical twins, which lead to the formation of shear bands by increasing the amount of deformation. Microstructural studies suggest that the decrease in the microhardness of cold-rolled samples is caused by the formation of strain-free grains on the shear bands. The development of strain-free grains is aided by the rotation of subgrains on the shear bands.

Effect of CNTs on microstructure, mechanical and wear properties of the AZ91–3B4C–3SiC–xCNTs composites

This article presents a study on the effect of adding carbon nanotubes (CNTs) (0, 0.5, 1 and 2 wt-%) and hot extrusion on the microstructures, mechanical properties, and wear behaviour of AZ91–3B4C–3SiC hybrid composites. The matrix alloy is AZ91 Mg alloy which primarily consists of 9 wt-% Al and 1 wt-% Zn. A mechanical-induction stir casting process was used to add CNTs to the composite. XRD patterns and EDX analysis showed that all composites have a microstructure of α-Mg, Mg17Al12, SiC and B4C. The outcomes demonstrated that the Mg17Al12 networks can be significantly thinned by the additional CNTs. The hot extrusion also dispersed the B4C and SiC particles in the structure, improving the particle-stimulated nucleation (PSN) plus twinning mechanism, but the presence of micron particles caused stress concentration, which did not affect the composites’ strength and elongation. The wear behaviour of the as-cast and extruded composites was studied by applying 5, 10 and 20 N forces at room temperature. The results showed that the mass loss and the coefficient of friction values are decreased with the addition of CNTs, which is attributed to the increased microhardness and self-lubricating properties of the CNTs.

Reconsideration of the dislocation arrest model for dynamic strain aging in C-bearing high Mn steel with low stacking fault energy

In the present study, we investigated the behavior of type A serration in the tensile flow curves measured at temperatures ranging from 273 K to 323 K with a strain rate of 1 × 10−3 /s, using high Mn steels with varying N contents. As a result, it was found that the critical engineering strain for the onset of type A serrations (ecA) increased with an increase in the N content at a given tensile temperature. This finding could not be explained by the conventional dislocation arrest model, which has been used to account for type A serrations occurring in C-bearing high Mn steels without N. Therefore, we attempted to explain the result by introducing the dynamic formation of obstacles to dislocation slip, such as mechanical twins and Lomer-Cottrell locks, during tensile deformation, a factor not considered in the conventional dislocation arrest model. However, the specific reason for the increase in the ecA value due to the addition of N was not elucidated. Therefore, we modified the dislocation arrest model based on the concept that the combination and cross-slip of screw partial dislocations, which accumulate at the obstacles, become more favorable due to an increase in stacking fault energy resulting from the addition of N. The modified dislocation arrest model successfully explained the influences of not only N content but also strain rate and tensile temperature on the ecA value in both C-bearing high Mn steels with and without N.

Cross-slip of extended dislocations and secondary deformation twinning in a high-Mn TWIP steel

Twinning-induced plasticity (TWIP) steels have become important materials in industry owing to the good combination of strength and ductility and high strain hardening rate. The excellent mechanical properties are highly related to the glide of dislocation and deformation twinning. However, the cross-slip behavior of the extended dislocation and the mechanism of deformation twinning are still controversial. Here, the partial dislocation motion and austenite twinning of a high-Mn steel at the early stage of deformation were investigated using in-situ tensile transmission electron microscope (TEM) technique. Results show that a large number of plane glide and cross-slip of extended dislocations can occur at the early stage of deformation. Extended dislocation nodes can be formed as a result of the reaction between adjacent extended dislocations on the same glide plane. In-situ tensile TEM experiments confirm two cross-slip models of partial dislocation: (1) the Friedel-Escaig model, cross-slip based on constriction of extend dislocation and re-dissociation; (2) the Fleischer model, cross-slip involving Lomer-Cottrell dislocation. Based on experimental results and energy calculations, it can be confirmed that the formation mechanism of austenite primary deformation twin induced by partial dislocations is different from that of secondary deformation twin. Grain boundary emits partial dislocation into the grain to form stable stacking fault which induces austenite primary deformation twin. The formation of secondary deformation twin is related to cross-slip of extended dislocation. Only the cross-slip of an extended dislocation containing a 90° partial dislocation can induce the formation of secondary deformation twin by introducing the Frank partial dislocation.

On the formation of Al2Si2Sr phase and its behavior in Al–Si–Sr alloys

Sr element is commonly used to modify eutectic Si in Al–Si alloys, while Al2Si2Sr phase is quite easy to precipitate when Sr content is high to tens of ppm level. In this study, the growth models of Al2Si2Sr crystal as well as its behavior in Al–xSi–2 Sr (x=5, 8, 12, 18, 25 and 40, wt%) alloys were investigated. Polyhedral, triangular pyramid and dendritic morphologies of Al2Si2Sr crystals were detected, and their growth models were discussed. Based on the crystallographic parameters, the disregistry between (0001)Al2Si2Sr and (111)Si is calculated to be 9.7%. Transmission electron microscopy analysis confirms that the Al2Si2Sr phase is not likely to be a good nucleation site for Si. Differential scanning calorimetry analysis indicates that Al2Si2Sr phase is firstly precipitated in Al–5, 8, 12, 18Si–2 Sr alloys, while its precipitating temperature is close to primary Si in Al–25Si–2 Sr alloy and it falls behind to primary Si in Al–40Si–2 Sr alloy. Interestingly, amounts of Al2Si2Sr dendrites were engulfed by primary Si in Al–40Si–2 Sr alloy. Based on the widely–known impurity–induced twinning mechanism in Sr modified Al–Si alloys, the Al2Si2Sr dendrites were deduced to be in–situ evolved from Sr–rich clusters, which are absorbed on {111}Si planes. This work may provide a new perspective for understanding the modification mechanisms of Sr element on Si crystal in Al–Si–Sr alloys.

Microstructural and isotopic analysis of shocked monazite from the Hiawatha impact structure: development of porosity and its utility in dating impact craters

U–Pb geochronology of shocked monazite can be used to date hypervelocity impact events. Impact-induced recrystallisation and formation of mechanical twins in monazite have been shown to result in radiogenic Pb loss and thus constrain impact ages. However, little is known about the effect of porosity on the U–Pb system in shocked monazite. Here we investigate monazite in two impact melt rocks from the Hiawatha impact structure, Greenland by means of nano- and micrometre-scale techniques. Microstructural characterisation by scanning electron and transmission electron microscopy imaging and electron backscatter diffraction reveals shock recrystallisation, microtwins and the development of widespread micrometre- to nanometre-scale porosity. For the first time in shocked monazite, nanophases identified as cubic Pb, Pb3O4, and cerussite (PbCO3) were observed. We also find evidence for interaction with impact melt and fluids, with the formation of micrometre-scale melt-bearing channels, and the precipitation of the Pb-rich nanophases by dissolution–precipitation reactions involving pre-existing Pb-rich high-density clusters. To shed light on the response of monazite to shock metamorphism, high-spatial-resolution U–Pb dating by secondary ion mass spectrometry was completed. Recrystallised grains show the most advanced Pb loss, and together with porous grains yield concordia intercept ages within uncertainty of the previously established zircon U–Pb impact age attributed to the Hiawatha impact structure. Although porous grains alone yielded a less precise age, they are demonstrably useful in constraining impact ages. Observed relatively old apparent ages can be explained by significant retention of radiogenic lead in the form of widespread Pb nanophases. Lastly, we demonstrate that porous monazite is a valuable microtexture to search for when attempting to date poorly constrained impact structures, especially when shocked zircon or recrystallised monazite grains are not present.

Enhancing the strength-ductility synergy in hot-forged Fe50Mn30Co10Cr10 high entropy alloy (HEA) through carbon additions

In this work, we systematically investigated the effect of carbon additions on the microstructure and room temperature mechanical properties of hot-forged Fe50Mn30Co10Cr10 HEA. The different carbon contents were introduced to Fe50-xMn30Co10Cr10Cx (x = 1, 2.5, 6 at.%, hereinafter, referred as C1, C2.5 and C6, respectively) HEAs to enhance the strength-ductility synergy by triggering the multiple strengthening mechanisms. The results showed that the grain sizes were decreased with increasing of carbon content, while a high fraction of mechanical twins ∼45% were generated in C2.5 HEA, and their fractions were ∼35% in C1 and C6 HEAs. Moreover, the discrete nano-sized M23C6 carbides in C2.5 HEA were transformed into continuous mico-sized M23C6 carbides along the grain boundaries in C6 HEA. Therefore, C2.5 HEA possessed high yield strength of 584 MPa, tensile strength of 1.03 GPa and outstanding ductility of 68%, i-e., breaking the strength-ductility paradox. A highest yield strength of∼662 MPa and tensile strength of more than 1 GPa were observed for C6HEA with refine grains, although the ductility was only ∼10%, which indicated that the massive carbon addition could effectively enhanced the strength of HEA but at the cost of ductility due to the presence of coarse M23C6 carbide precipitation. The enhanced mechanical properties of studied HEAs are mainly ascribed to the contribution of multiple strengthening mechanisms including precipitation, grain boundary, dislocation and interstitial solid solution strengthening.

Effect of N on microstructure evolution and strain hardening of high-Mn austenitic steel during tensile deformation

The present study investigated the microstructure evolution and strain hardening of two types of high-Mn austenitic steels, i.e., Fe−18.5Mn–7Cr−0.6C (00 N) and Fe−18.5Mn–7Cr−0.6C−0.21 N (21 N), during tensile deformation. The results revealed that the addition of N increased the yield and tensile strength of high-Mn austenitic steel with almost no loss of elongation. The strain hardening of the 00 N and 21 N steels was closely related to the microstructure evolution. At the initial tensile deformation stage, dislocation slip was the dominant deformation mechanism of the two test steels. Due to the addition of N, the dislocation cross-slip in the 21 N steel was suppressed, leading to a higher strain hardening rate. With the increase of true strain, the mechanical twins became active. At a true strain of 0.18, a unique network structure of mechanical twins and dislocation cells was formed in the 00 N steel, and the thickness and spacing of mechanical twins were lower, which increased the resistance of dislocation motion and made its strain hardening rate slightly higher than that of the 21 N steel. However, at a true strain of 0.37, the thickness and spacing of mechanical twins in the 21 N steel decreased rapidly, which increased the difficulty of dislocation movement, resulting in a higher strain hardening rate than that of the 00 N steel. In short, the increased resistance of dislocation motion was the fundamental reason for the enhanced strain hardening rate, rather than mechanical twins.

Excellent ductility of an austenitic stainless steel at a high strength level achieved by a simple process

In the pursuit of simultaneously improving the yield strength and plasticity of austenitic stainless steel, a new austenitic stainless steel was fabricated by induction smelting using a pure N2 atmosphere, hot forging, cryogenic rolling, and annealing. The material was characterized by microstructures with 3–4 μm uniform finer grains, fine precipitates, high thermal stability austenite, and extensive high-angle grain boundaries. The elongation after fracture, yield strength, and ultimate tensile strength of the samples reached 53.5 %, 707 MPa, and 1020 MPa, respectively, as well as 61 %, 600 MPa, and 977 MPa, respectively, at the same time. Moreover, a high strain hardening rate was achieved in the new stainless steel. The appropriate uniform finer grains not only played a role in grain-refined strengthening but also provided intragranular spaces and sufficient mean free available paths for dislocation accumulation and movement. Precipitates, which were coherent or semi-coherent with the matrix, provided interfaces for dislocation accumulation and obstructions for dislocation movement. Extensive high-angle grain boundaries with appropriate finer grains served as another important factor for excellent ductility due to the inhabitation and resulting deviation of crack propagation. In addition, strain-induced mechanical twinning in the current austenitic stainless steel contributed to excellent ductility and high strength.

Surface modification and enhanced wear performance through severe shot peening treatment in 316L stainless steel manufactured by metal injection moulding

This study investigates the micro-to nanostructural evolution, hardness, and linear reciprocating wear resistance, using Al2O3 ball as a counterpart of 316L stainless steel fabricated by the metal injection moulding (MIM) process, with and without severe shot peening treatment (SSP). SSP treatment led to a slight increase in Ra but a decrease in Rz and the formation of nanocrystalline surface, α′-martensite and mechanical twin. The subsurface hardness increased significantly. Surprisingly, the coefficient of friction remained constant (0.37–0.56) and depended solely on the testing load, despite alterations in surface roughness and subsurface microstructure due to SSP treatment. Furthermore, wear resistance notably improved under 10 N and 20 N loads, attributed to the surface modification by SSP treatment, but showed no significant difference at 30 N. The wear mechanisms, including abrasive, adhesive wear, and oxidative wear, remained similar, with adhesive and oxidative wear dominating at lower testing loads (10–20 N). However, with a testing load of 30 N, the strengthening effect of SSP treatment was surpassed, leading to the dominance of severe adhesive and oxidative wear. Consequently, the wear resistance exhibited insignificant differences between specimens before and after SSP treatment.

Dislocation structure evolution during room temperature dwell loading of a Ti-6Al-4 V alloy

The current work examines the evolution of the dislocation structure, within both the α and β phases, of a Ti-6Al-4 V alloy subjected to room temperature dwell loading performed at about 96% of the macroscopic yield stress level for several durations, as part of a synchrotron in-situ deformation experiment. The obtained findings represent a vital contribution to creating a scientific basis for improving lifing predictions for aero-propulsion components. The dislocation configuration, type and density were examined post-mortem using transmission electron microscopy (TEM). Despite the relatively low applied stress level, well-developed dislocation structures were already formed within the α phase at a dwell duration of 10 min and changed only modestly up to 60 min. The plastic deformation of the above phase took place solely via dislocation slip. To facilitate a comparison between different dwell durations, the TEM investigation focused on the regions oriented for the prismatic glide that represented the main deformation mode due to the starting crystallographic texture. After deformation, the regions oriented for the prismatic slip contained planar slip bands largely consisting of dislocations of a screw type. There was rather limited interaction between different bands, as the dislocation arrays passed through the slip band intersections with only minor difficulty. The screw-type dislocations seemed to preferentially form during straining. Dislocation Burgers vectors experimentally determined within the β phase occasionally departed from the Schmid rule and such dislocations typically showed a prevalent screw component. Some deformation banding and {112} 〈111〉 − type mechanical twin formation were locally detected within the β phase.

The anisotropy of deformation twinning in bcc materials: Mechanical loading, temperature effect, and twin–twin interaction

By integrating atomistic simulations with theoretical calculations, we investigate the prevalence of {112} deformation twins in bcc materials and their sensitivity to the loading direction as well as temperature. Our atomistic simulations reveal the copious occurrence of {112} twins involving either hcp or fcc intermediate phases. The hcp and fcc cases occur in bcc titanium alloy during [100] compression and tension, respectively. Similarly, they can also manifest in bcc iron under different temperature conditions. Furthermore, by calculating the correspondence matrix, we identify the fcc and hcp cases as the normal deformation twin mode and the 1/2 atoms-shuffle mode, respectively. The twinning modes have a significant influence on twin–twin interactions and the final microstructure. Our theoretical calculation confirms that the selection of specific twin modes and twin variants is governed by the correlation between their deformation path and mechanical loading. The results underscore the crucial role of mechanical loading and temperature in activating the specific twin modes, thereby providing a novel avenue for engineering twin microstructures through carefully designed thermomechanical processing techniques.

A Review of Deformation Mechanisms, Compositional Design, and Development of Titanium Alloys with Transformation-Induced Plasticity and Twinning-Induced Plasticity Effects

Metastable β-type Ti alloys that undergo stress-induced martensitic transformation and/or deformation twinning mechanisms have the potential to simultaneously enhance strength and ductility through the transformation-induced plasticity effect (TRIP) and twinning-induced plasticity (TWIP) effect. These TRIP/TWIP Ti alloys represent a new generation of strain hardenable Ti alloys, holding great promise for structural applications. Nonetheless, the relatively low yield strength is the main factor limiting the practical applications of TRIP/TWIP Ti alloys. The intricate interplay among chemical compositions, deformation mechanisms, and mechanical properties in TRIP/TWIP Ti alloys poses a challenge for the development of new TRIP/TWIP Ti alloys. This review delves into the understanding of deformation mechanisms and strain hardening behavior of TRIP/TWIP Ti alloys and summarizes the role of β phase stability, α″ martensite, α′ martensite, and ω phase on the TRIP/TWIP effects. This is followed by the introduction of compositional design strategies that empower the precise design of new TRIP/TWIP Ti alloys through multi-element alloying. Then, the recent development of TRIP/TWIP Ti alloys and the strengthening strategies to enhance their yield strength while preserving high-strain hardening capability are summarized. Finally, future prospects and suggestions for the continued design and development of high-performance TRIP/TWIP Ti alloys are highlighted.

Microstructure evolution and its effect on corrosion behavior during cold rolling of Ti–Nb–Ni sheet as bipolar plates substrate for PEMFC

In this work, hot rolled Ti–Nb–Ni sheet with thickness of 1.8 mm was subjected to cold rolling with different reductions (20 %, 40 %, 60 %, 75 % and 85 %). Microstructure evolution and corrosion resistance of sheets with and without being cold rolled were investigated. Mechanical twins are generated for 20 % and 40 % cold rolled sheets, while dislocation slip becomes dominant for reductions larger than 40 %. Typical TD-split basal texture was observed in all of specimens. Corrosion resistance of the sheets in solution of pH = 3 H2SO4 with 0.1 ppm F− at 80 °C were evaluated. All the sheets possessed corrosion current densities lower than 1 μA cm−2, meeting the requirement of Department of Energy. Hot rolled sheet possessed the noblest OCP (−0.212 V), lowest corrosion current density (0.15 μA cm−2) and steady state current density (0.012 μA cm−2), as well as the largest polarization resistance of all the sheets (749.1 kΩ cm2). Besides, corrosion resistance for cold rolled sheets becomes inferior with reduction increasing. This can be attributed to increased dislocation density which provides more available active sites and deteriorates corrosion resistance with reduction increasing. Therefore, to obtain desirable corrosion resistance in PEMFC environment, Ti–Nb–Ni sheets with microstructure possessing massive dislocations should be avoided.

Microstructural evolution and tribological properties of TC6 titanium alloy strengthened by laser peening combined with nitrogen ion implantation

To obtain a combined strengthening layer and further redouble the ability to resist wear of TC6 titanium alloy, an innovative technique of laser peening plus nitrogen ion implantation was proposed. The tribological properties of the specimen subjected to combined laser peening and nitrogen ion implantation were analyzed using transmission electron microscope, nanoindentation tester, sliding friction wear tester and scanning electron microscopy. The results showed that laser peening combined with nitrogen ion implantation induced a higher density of dislocation than that produced only by laser peening or nitrogen ion implantation. Compared with the ion implanted and laser peened samples, the surface nano-hardness subjected to combined strengthening process was increased by 21.3 % and 5.8 %. Moreover, the friction coefficient of combined processed specimen reduced to 0.4, the wear tracks depth and width were about 19.02 μm and 300 μm, while the wear mechanism was mainly abrasive and oxidative wear. The dislocations, sub-grains and mechanical twins produced by laser peening provided large amounts of diffusion channels for ion implantation, which conferred better wear resistance than the samples processed only by laser peening or nitrogen ion implantation.

Modelling of grain size effects in progressive microforming using CPFEM

Progressive microforming is widely recognized as one of the most efficient and desirable methods of mass production in micromanufacturing arena. To predict the deformation behaviour and size effects of materials induced in progressive microforming, the finite element method (FEM) employed for modelling the microforming process needs to account for microstructure details and deformation/failure mechanisms of the materials. This led to the development of the novel crystal plasticity finite element method (CPFEM) and cohesive zone model (CZM). Previous research and application of CPFEM have been mainly limited to simple deformations such as uniaxial tension and compression, whereas the new method can provide physical insights into how the grain size affects the interplay between crystallographic slip and mechanical twinning in complex microforming, and further material deformation during sheet blanking. A case study was conducted to manufacture a hexagonal socket part using a three-step progressive microforming system, with the comparison between experiments and CPFEM simulations focusing on microstructure evolution, deformation load, and product quality. The CPFEM was found to be more reliable than the conventional FEM in predicting complex deformation, particularly in microstructure and texture evolution, dimensional accuracy and irregular geometries. Results showed that the total height of the part increases with the decreasing grain size, while the head diameter rises with grain size. Simulations successfully anticipated the distributions of dead metal zones and shear bands and identified hole and rollover geometries and corresponding grain size effects. In conclusion, this research facilitates the understanding of grain size effects on the deformation behaviour in progressive microforming and presents a novel approach and strategy for modelling, prediction, and product quality assurance in complex micro deformation and forming processes.

Microstructure Features and Mechanical Properties of Modified Low-Activation Austenitic Steel in the Temperature Range of 20 to 750 °C

A new low-activation austenitic steel with a modified composition and high austenite stability is proposed. The features of its microstructure after solution treatment (ST) and cold rolling (CR) are studied. The mechanical properties and features of the fracture behavior of this steel under tensile tests in the temperature range of 20–750 °C are discussed. After ST, an austenitic structure with stacking faults and dispersed carbide particles of the MC and M23C6 types is observed in the steel. After CR, the grains are refined, and the average grain size decreases from 41.4 µm (after ST) to 33.9 µm. High-density microtwin packets form in the material, and the dislocation density increases relative to that after ST. As the test temperature increases from 20 to 750 °C, the yield strength of the steel decreases by approximately two times, from ≈300 to 150 MPa (for ST) and from ≈700 to 370 MPa (for CR). In the studied temperature range, the steel demonstrates up to 2.6 times higher values of elongation to failure, ≈40–80% (for ST) and ≈13–27% (for CR), compared to steels of similar compositions and lower manganese content. Mechanical twinning contributes to the high steel ductility up to 300 °C. Signs of discontinuous flow in the tensile curves after ST in the temperature range of 500–600 °C and a decrease in the elongation to failure in the close temperature range indicate dynamic strain aging (DSA). Steel fracture after tension at all test temperatures mainly occurs via a ductile dimple transcrystalline mechanism with elements of ductile intercrystalline fracture. It is shown that cracks nucleate on clusters of dispersed second-phase particles. The mechanisms of plastic deformation, fracture, and strengthening of the proposed modified low-activation austenitic steel are discussed.

Heterogeneous microstructural evolution during hydrodynamic penetration of a high-velocity copper microparticle impacting copper

Microparticle hydrodynamic penetration (HDP) may be associated with the erosion regime in cold spray processing and other high-velocity impact events. Here, in an experimental approach where we can individually launch particles and study the impact sites, we explore copper microparticles impacted on copper substrates at velocities above 900 m/s where HDP begins. We lift cross-sectional lamellae from the impact sites with a focused-ion beam for further microstructural characterization using electron backscatter diffraction and scanning transmission electron microscopy. Due to the gradients of strain, strain rate, and temperature associated with HDP, heterogeneous microstructures result. The structural evolution processes observed include deformation twinning and multiple dislocation-mediated grain recrystallization mechanisms—geometric dynamic recrystallization (gDRX), discontinuous DRX (dDRX), and meta DRX (mDRX). The higher strains at the interface lead to the most significant structural changes and complex mechanisms. In contrast, there is a gradient to more conventional dislocation plasticity away from the interface (on either the particle or substrate side). These microstructural observations are consistent with the deformation map for copper and extend the observations of impact-induced recrystallization across new regimes of behavior.

On the orientation-dependent mechanical properties of interstitial solute-strengthened Fe49.5Mn30Co10Cr10C0.5 high entropy alloy produced by directed energy deposition

Interstitial solute-strengthened Fe49.5Mn30Cr10Co10C0.5 (at%) high entropy alloy was additively manufactured by directed energy deposition (DED) process in this work. While the as-deposited material exhibits an excellent combination of strength and ductility, the effect of anisotropy on the mechanical performance of the DED processed component was studied in detail. The ultimate tensile strength (UTS) of the horizontal tensile sample with a main fiber texture of <111> // tensile direction (TD) went up to 1 GPa while maintaining a superb failure elongation of 36%. The vertical tensile sample, with a dominant <001> // TD texture, failed at an UTS of 750 MPa with an enhanced failure elongation of 52%. Microstructural analysis of the deformed samples showed that the horizontal samples were mainly deformed via the formation of mechanical twins, whereas the twining activity was less profound in the vertical samples. Single crystal micro-pillar compression testing revealed that the deformation mechanism complies well with the Schmid’s factor. In addition, a higher critical resolved shear stress for twining compared to slip was also confirmed in the micro-pillar compression testing.