Fe50Mn30Co10Cr10 High-entropy Alloy Research Articles

Bidirectional transformation enabled improvement in strength and ductility of metastable Fe50Mn30Co10Cr10 complex concentrated alloy under dynamic deformation

High strain rate compression experiments performed on a non-equiatomic metastable fcc + hcp Fe50Mn30Co10Cr10 high entropy alloy using split Hopkinson pressure bar setup shows improved flow stress and compression ductility compared to quasistatic deformed samples. The deformation response was characterised by the occurrence of hardening and softening stages compared to sustained strain hardening for quasistatic deformation. Detailed EBSD, BSE imaging analysis coupled with TEM shows significant bi-directional transformation (B-TRIP) and increased fcc γ phase stability in high strain rate regime while only forward (fcc to hcp) transformation dominates with increasing fraction of hcp ε phase in the quasistatic regime of deformation. Bidirectional transformation aided by adiabatic heating and heterogeneous deformation in the high strain rate regime leads to optimal stress and strain partitioning between the two phases and delays the initiation of damage at the interface. The presence of concomitant strain rate hardening and improvement in ductility in the dynamic deformation regime opens up avenues for microstructural tunability to achieve simultaneous improvement in strength and ductility using the metastability paradigm in complex concentrated alloys.

Microstructure and tensile properties of metastable Fe50Mn30Co10Cr10 high-entropy alloy prepared via powder metallurgy

With the characterization of microstructure and tensile properties, the feasibility of preparing Fe50Mn30Co10Cr10 high-entropy alloys (HEAs) via powder metallurgy was explored, and the effect of sintering temperature and deformation temperature on the microstructure and tensile properties of the alloy was investigated. The alloys sintered at different temperatures possessed a dual-phase structure with face-centered cubic (FCC) and hexagonal close-packed (HCP). The average grain size, HCP phase fraction, and twinning boundary fraction increased with the sintering temperature. The best combination of strength and ductility was obtained in the alloy sintered at 1000 °C, which exhibited a strongly temperature-dependent mechanical behavior, i.e., when the deformation temperature decreased from 298 to 77 K, the yield strength and ultimate tensile strength increased from ∼287 to ∼490 MPa and from ∼745 to ∼1107 MPa, respectively, with only a tiny loss of uniform elongation; this is mainly attributed to the deformation mode of the alloy varied with deformation temperature. During tensile deformation at 298 K, dislocation slip, phase transformation, detwinning of annealing twins, and mechanical twinning were the dominant mechanisms, while no mechanical twinning was activated at 77 K. The excellent combination of strength and ductility for the alloy at 77 K relative to 298 K is mainly attributed to a more significant TRIP effect. Powder metallurgy can be used as a promising way for manufacturing metastable high entropy alloys with excellent tensile properties.

Enhanced strength-ductility synergy in NbC-reinforced FeMnCoCr high entropy alloy with heterostructure by adopting a novel process

We explored a novel heterostructure design strategy to simultaneously enhance the strength and ductility of NbC-reinforced FeMnCoCr high-entropy alloys by adopting grain-scale strain localization regulation coupling partial recrystallization annealing, and the effect of cold-rolled microstructure on annealed microstructure evolution and mechanical properties was studied. The transformation-induced plasticity (TRIP) effect and the dislocation density decreased as the grain size increased. The significant grain-scale strain localization and obvious Brass and A textures were observed in the cold-rolled microstructure of the large grain samples. Recrystallization preferentially occurred in the high-strain region during annealing leading to heterogeneous recrystallization nucleation. The recrystallization kinetics of A texture was slow and remained in the partially recrystallized microstructure. A heterostructure with a bimodal grain size distribution was formed in coarse-grained samples. The heterostructure with coarse un-recrystallized grains wrapped by recrystallized grains has good comprehensive mechanical properties. Its yield strength was 1.4 times that of a fine-grained microstructure sample, while maintaining excellent strain hardening capacity without decreasing elongation. The high yield strength was attributed to dislocation strengthening. The TRIP effect appeared earlier in the coarse un-recrystallized grains with low dislocation density under tension, and the back stress strengthening and TRIP effect improved the strain hardening capacity.

Microstructures, Mechanical and High-Temperature Tribological Properties of Dual-Phase Fe50Mn30Co10Cr10 High-Entropy Alloy Fabricated by Laser Metal Deposition

Microstructures, Mechanical and High-Temperature Tribological Properties of Dual-Phase Fe50Mn30Co10Cr10 High-Entropy Alloy Fabricated by Laser Metal Deposition

Atomistic simulations of martensitic transformation processes for metastable FeMnCoCr high-entropy alloy

Atomistic simulations of martensitic transformation processes for metastable FeMnCoCr high-entropy alloy

Effect of the amount of SiC particles on the microstructure, mechanical and wear properties of FeMnCoCr high entropy alloy composites

Ceramic particle reinforced high entropy (HEA) alloy composites have attracted considerable attention due to their excellent combination of strength, ductility, and wear resistance. In this work, the high entropy alloy composites (Fe 50 Mn 30 Co 10 Cr 10 matrix) with the different SiC contents (0.1, 0.5, 1, and 3 vol%) were fabricated by arc melting. The effect of SiC content on microstructure characteristics, mechanical and wear properties of Fe 50 Mn 30 Co 10 Cr 10 composites were studied. The results showed that SiC stabilized the γ phase and refined the grain sizes. In addition, the number of ε variants were decreased with refined grain sizes. The composite with 1 vol% SiC optimized the combination of ultimate tensile strength and ductility, which is attributed to grain-boundary strengthening, twin boundary strengthening, dispersion strengthening and load-bearing strengthening. Simultaneously, the optimized composite with 1 vol% SiC displayed the best wear friction ability, in which the proper SiC content played a key role in carrying load during friction. • Fe 50 Mn 30 Co 10 Cr 10 with four different SiC contents (0.1, 0.5, 1, and 3 vol%) are prepared by the arc-melting. • SiC particles promote phase transformation from ε to γ, refine the grain sizes and decrease the number of ε variants. • Fe 49 Mn 30 Co 10 Cr 10 SiC 1 composite optimizes the combination of ultimate tensile strength and ductility. • Fe 49 Mn 30 Co 10 Cr 10 SiC 1 composite displays the best wear friction ability.

Effects of carbon addition on microstructure and mechanical properties of Fe50Mn30Co10Cr10 high-entropy alloy prepared by powder metallurgy

To improve the mechanical properties of Fe50Mn30Co10Cr10 high entropy alloy (HEA), a series of carbon-containing HEAs based on Fe50Mn30Co10Cr10 were successfully prepared by powder metallurgy. The effects of carbon content on microstructural evolution and mechanical properties of the as-sintered HEAs were investigated. The improved FCC phase stability and the decreased Σ3 twin grain boundary proportion as the increase of carbon content are mainly due to the increased stacking fault energy. As the carbon content increases, the phase structure of the as-sintered HEAs changes from FCC + HCP phases to FCC phase and then to FCC + M23C6 phases, and the deformation-induced martensitic transformation from FCC to HCP weaken gradually. The solid solubility of carbon in the as-sintered Fe50Mn30Co10Cr10 HEAs is below 2 at.%. A large number of carbides can be observed in the microstructure of the alloys at higher carbon content. The yield strength of the alloys increases approximately linearly with carbon content, while the uniform elongation first increases and then decreases. The (Fe50Mn30Co10Cr10)98C2 HEAs with nano-carbides and ultrafine manganese oxide exhibited a yield strength of 362 MPa, an ultimate tensile strength of 792 MPa, and uniform elongation of 36.7%, showing simultaneous improvement in strength and ductility compared with the carbon-free alloy. This is due to the joint contribution of multiple strengthening mechanisms in the carbon-containing HEA. Interstitial solid solution strengthening and grain boundary strengthening act as the dominant strengthening mechanism. Alloying with carbon element is a feasible method to enhance the mechanical properties of HEAs prepared by powder metallurgy.

Ratcheting behavior of non-equiatomic TRIP dual-phase high entropy alloy

Ratcheting behavior of metastable dual-phase (FCC+HCP) Fe50Mn30Co10Cr10 high entropy alloy has been investigated for various combinations of mean stress(σm) and stress amplitude (σa) at ambient temperature. The experimental results show that the accumulation of ratcheting strain and fatigue life primarily depend on the applied mean stress and stress amplitude combination. Detailed microstructure analyses using electron back scattered diffraction (EBSD), transmission electron microscopy (TEM), and transmission Kikuchi Diffraction (TKD) revealed the activation of multiple deformation mechanisms, including planar slip, deformation-induced twinning (TWIP), and deformation-induced martensitic phase transformation (TRIP) in both the phases. The synergistic operation of these mechanisms with reverse HCP to FCC transformation at local stress concentration regions in the microstructure promoted cyclic hardening leading to an improved low cycle fatigue behavior of the TRIP DP-HEA under asymmetrical stress-controlled cyclic deformation. In a nutshell, the operation of multiple factors responsible for twinning is unique, providing means to design novel multicomponent alloys.

Corrosion engineering boosting bulk Fe50Mn30Co10Cr10 high-entropy alloy as high-efficient alkaline oxygen evolution reaction electrocatalyst

• The self-supported HEA catalyst was prepared by corrosion engineering. • Amorphous honeycomb nano-hydroxides are obtained on the HEA surface. • HEA-250Ni demonstrates the high OER activity and excellent stability. • The excellent performance is due to its special structure and diverse valence states. • Our findings open up a new avenue to prepare large-scale HEA as electrocatalysts. Oxygen evolution reaction (OER) is a critical process in electrocatalytic water splitting. However, the development of low-cost, highly efficient OER electrocatalysts by a simple method that can be used for industrial application on a large scale is still a huge challenge. Recently, high entropy alloy (HEA) has acquired extensive attention, which may provide answers to the current dilemma. Here, we report bulk Fe 50 Mn 30 Co 10 Cr 10 , which is prepared by 3D printing on a large scale, as electrocatalyst for OER with high catalytic performance. Especially, an easy approach, corrosion engineering, is adopted for the first time to build an active layer of honeycomb nanostructures on its surface, leading to ultrahigh OER performance with an overpotential of 247 mV to achieve a current density of 10 mA cm −2 , a low Tafel slope of 63 mV dec −1 , and excellent stability up to 60 h at 100 mA cm −2 in 1 M KOH. The excellent catalytic activity mainly originates from: (1) the binder-free self-supported honeycomb nanostructures and multi-component hydroxides, which improve intrinsic catalytic activity, provide rich active sites, and reduce interfacial resistance; and (2) the diverse valence states for multiple active sites to enhance the OER kinetics. Our findings show that corrosion engineering is a novel strategy to improve the bulk HEA catalytic performance. We expect that this work would open up a new avenue to fabricate large-scale HEA electrocatalysts by 3D printing and corrosion engineering for industrial applications.

Microstructure and Properties of Laser-cladded Fe50Mn30Co10Cr10 High Entropy Alloy Coatings

Microstructure and Properties of Laser-cladded Fe50Mn30Co10Cr10 High Entropy Alloy Coatings

Effect of the Amount of Sic Particles on the Microstructure, Mechanical and Wear Properties of Femncocr High Entropy Alloy Composites

Effect of the Amount of Sic Particles on the Microstructure, Mechanical and Wear Properties of Femncocr High Entropy Alloy Composites

Hetero-deformation-induced (HDI) plasticity induces simultaneous increase in both yield strength and ductility in a Fe50Mn30Co10Cr10 high-entropy alloy

Low yield strength is the bottleneck of the face-centered cubic-structured high-entropy alloys (HEAs). Here, the strategy of hetero-deformation-induced (HDI) plasticity is applied by hetero-structuring to induce strengthening and strain hardening for a simultaneous increase in both yield strength and ductility in a Fe50Mn30Co10Cr10 HEA. The coarse-grain (CG) microstructure is a dual phase consisting of face-centered cubic (γ) and hexagonal close-packed (ε) phases, along with phase transformation from γ to ε to happen during tensile deformation. The hetero-structure (HS) was designed, besides recrystallized γ and ε, specifically to reserve a part of deformed γ after cold rolling followed by incomplete recrystallization. Yield strength increases from 200 MPa in CG to 760 MPa in HS, while uniform elongation (i.e., ductility) increases from 35% to 38%. The tensile load-unload-reload testing showed the ceaselessly presence of hysteresis loop during each unload-reload cycle. Both the residual plastic strain and HDI stress were measured with tensile strains in both HS and CG, providing solid evidence of the effect of HDI plasticity. To be specific, the HDI stress is found to account for a large proportion of global flow stress in HS as compared to that in CG. It turns out that the HDI plasticity facilitates both HDI strengthening and HDI strain hardening, which play the crucial role in enhancing strength and ductility. The microstructural origin of HDI plasticity in HS was ascribed to plastic incompatibility at hetero-interfaces of among varying grains as evidenced by the evolution of Schmid factor and KAM values as well.

Excellent plasticity of C and Mo alloyed TRIP high entropy alloy via rolling and heat treatment

The transformation-induced plasticity (TRIP) Fe50Mn30Co10Cr10 high entropy alloy (HEA) with 2 at% C and 1 at% Mo microalloying was prepared by non-consumable vacuum arc melting furnace. The as-casted alloy was then rolled at 70% and then annealed at 1000 °C for different times. The microstructure evolution and mechanical properties of the C and Mo alloyed TRIP-HEA were systematically investigated. The results showed that with the increase of annealing time, the strength of the C2Mo1 HEA increases, but the plasticity increases first and then decreases. Spuriously, when C2Mo1 HEA was annealed for 5 min at 1000 °C after 70% cold rolling, the total elongation was 121%, the tensile strength was 816 MPa, and its product of tensile strength and plasticity was 99.23 GPa, which is much better than the majority of HEAs. In the process of tensile deformation, <001> + <100>//TD double texture are formed, and dislocation slip and twin mechanism competed by each other, which affect the microstructure evolution in the process of plastic deformation, and finally as the great contribution to the product of tensile strength and plasticity.

Effects of NbC content on microstructural evolution and mechanical properties of laser cladded Fe50Mn30Co10Cr10-xNbC composite coatings

In this paper, NbC reinforced Fe50Mn30Co10Cr10 high entropy alloy coatings with different NbC content were fabricated by laser cladding. The formation mechanism of NbC particles with micro/nano-scale was analyzed. Based on the interaction between the solid-liquid interface and NbC particles, the distribution of micro/nano-scale NbC particles is clarified. The effects of NbC content on microstructure and mechanical properties of the coatings were investigated. It demonstrated that the nanoscale NbC particles restricted the dendritic growth whilst promoting grain nucleation and altering the grain morphology from columnar grain to equiaxed dendrite. Besides, the influence of NbC particles on FCC phase stability was studied based on the lattice mismatch theory, which indicates that the addition of ceramic particles is a new way to modify the phase volume fraction in the dual-phase high-entropy alloys (HEA). The micro-hardness and wear resistance of the coatings significantly improved with the increase of NbC content. For the Fe50Mn30Co10Cr10-30 wt%NbC high entropy composite coating, the average Vickers hardness and friction coefficient value separately is 525 HV and 0.45. In addition, the large fluctuations on the friction coefficient of the coatings for 10 wt% and 20 wt% NbC addition may be related to the uneven distribution of nanoscale NbC particles in the matrix.

Chemical short-range order in Fe50Mn30Co10Cr10 high-entropy alloy

Chemical short-range order (CSRO) is generally possible in concentrated solid solutions and currently of considerable interest for multi-principal element alloys. However, a convincing demonstration of CSRO has been challenging and achieved thus far only for ternary medium-entropy alloys such as VCoNi. Here, we report definitive proof of CSRO in a quaternary face-centered-cubic Fe50Mn30Co10Cr10 high-entropy alloy, acquired from systematic electron microscopy experiments. The evidence includes extra diffuse disks in nano-beam electron diffraction patterns, images in state-of-the-art aberration-corrected scanning transmission electron microscope, as well as compositional profiles across neighboring atomic planes/columns in atomic-resolution chemical maps. The CSRO regions are found to occupy an areal fraction of 20% and have dimensions on a sub-nanometer scale. This length scale, as well as the diffraction features of the CSRO, are different from those of intermetallic compound precipitates; as such, the CSRO is not a growing stage of a nucleated second phase, the precipitation of which has been dealt with previously in classical alloys. We further conducted a spatial correlation analysis of the concentrations in atomic columns in the chemical map, enabling us to uncover a general tendency toward nearest-neighbor chemical ordering, specifically, preference for unlike species (such as Fe–Mn) and avoidance for like-species (such as Fe–Fe). The persistence of this trend, the same as that found in VCoNi MEA, recently, is somewhat intriguing for a high-entropy alloy in which all the constituent elements are similar in atomic size and have rather a small enthalpy of mixing.

Effect of B4C particles addition on microstructure and mechanical properties of Fe50Mn30Co10Cr10 high-entropy alloy

High entropy alloy used as the metallic matrix of composites gives birth to a new family of composites. In this work, the effect of B4C particles on microstructure and mechanical properties of Fe50Mn30Co10Cr10 high-entropy alloy matrix is systematically investigated. B4C particles can stabilize austenite (γ) phase to form single γ phase and effectively refine grain size. Two different sizes and compositions of B4C particles are formed in B4C/Fe50Mn30Co10Cr10 composite. The fine B4C particles with the lower Cr contents can induce significant coherent strain and then strengthen the matrix, while the coarse B4C particles with the higher Cr content can induce micro-crack at the B4C/matrix interface due to the low interfacial metallurgical bonding. As compared to Fe50Mn30Co10Cr10 matrix, B4C/Fe50Mn30Co10Cr10 composite shows the higher tensile strength with the relative lower fracture strain. In addition, the composite possesses a better ability of wear friction than the matrix, revealing the oxidative wear and abrasive wear mechanism.

Yield strength insensitivity in a dual-phase high entropy alloy after prolonged high temperature annealing

Recent studies of FeMnCoCr-based high entropy alloys have demonstrated uncommon deformation behaviors such as transformation-induced plasticity, which were largely believed to be restricted to select families of steels. Coupled with the potential for entropy stabilization of high symmetry phases at high temperatures, this system represents a promising class of materials for structural applications in extreme environments. Yet, transformation-induced plasticity mechanisms are notably sensitive to microstructure parameters and the literature offers examples of deleterious decomposition of high entropy alloys under heat treatment, which raises concerns of resiliency in mechanical performance. Here, we evaluate the evolution of microstructure and mechanical properties of a FeMnCoCr high entropy alloy after prolonged heat treatment at high temperature. Microstructures are found to retain their characteristic austenite/martensite features, with parent face-centered cubic grains partitioned by hexagonal close-packed laths after heat treatment at 1200 °C for up to 48 hours. Results of mechanical testing reveal an unusual insensitivity of this alloy to grain growth-induced weakening effects. Namely, the yield strengths of FeMnCoCr samples are observed to remain constant across all heat treatment conditions, despite a near four-fold increase in the grain size. Close examination of post-heat treatment microstructures reveals a dramatic decrease in the inter-lath spacing at longer durations, which segments parent austenite grains. This crystal partitioning counteracts conventional grain growth-induced weakening by introducing additional barriers for dislocation pile-up. These results offer new insights into the mechanical resiliency of this transformation-induced plasticity high entropy alloy under prolonged high temperature heat treatment.

Additive manufacturing of TRIP-assisted dual-phases Fe50Mn30Co10Cr10 high-entropy alloy: Microstructure evolution, mechanical properties and deformation mechanisms

Abstract The metastable dual-phase non-equiatomic Fe50Mn30Co10Cr10 high entropy alloy (HEA) was successfully prepared via laser melting deposition (LMD) technique. The phase composition, microstructure and mechanical performance were systematically characterized at different sections of LMDed HEA samples. The as-printed HEA specimens were dominated by FCC γ phase, plate and needle-like HCP e phase, and high density stacking faults and dislocations were observed at high magnification. The as-printed samples exhibited anisotropic mechanical properties, together with the maximum ultimate tensile strength of 760 MPa and maximum elongation of 28%. The fracture surface along X and Z directions exhibit smooth curve shape, while the fracture surface along Y direction shows saw tooth shape, indicating the boundary of melt pool is weakly bounded. After deformation, the deformation bands were observed in the FCC matrix, showing that the plastic strain was controlled by FCC γ phase. In addition, stacking faults, dislocation increase significantly owing to the formation of stacking fault is caused by sliding of Shockeley partial dislocation, and the stacking fault is the core of HCP martensite nucleation.

Decelerated grain growth kinetic and effectiveness of Hall-Petch relationship in a cold-rolled non-equiatomic high entropy alloy

The present work deals with the grain growth behavior and mechanical properties of a cold-rolled non-equiatomic metastable Fe50Mn30Co10Cr10 high entropy alloy. The bimodal grain size distribution which was developed during isothermal annealing at the temperature range of 750–1050 °C, was gradually annihilated through increasing the annealing time. This was due to the higher capability of fine grains to grow up compared with coarse grains. The obtained grain growth exponents and grain growth activation energies were well higher than those reported for solid solution alloys and also reported for five component CoCrFeMnNi high entropy alloy. The extremely low grain growth kinetics of the experimented alloy even at high homologous temperature was discussed regarding the solute drag like effect of whole-solute matrix in addition to the sluggish diffusion as an intrinsic properties of high entropy alloys. The variation in mechanical properties of the experimented alloy was mainly discussed relying on the effectiveness of Hall-Petch relationship and the stability of the matrix. It was found that the grain boundaries acted as an effective barrier against dislocation motion, and caused postponement of the strain induced transformation leading to an acceptable strength/ductility balance.

Multi-heterostructure and mechanical properties of N-doped FeMnCoCr high entropy alloy

High-entropy alloys (HEAs) have been extensively studied in recent years. However, yield strength of HEAs in which austenite is the dominating phase is usually low, far from satisfying the engineering demands. Improving performance-cost ratio of such alloys will help for their practical structural applications. Here we report a novel strategy to produce ultrastrong, tough, and low-cost HEAs, in which heavy nitrogen-doping (2.6 at.%) was applied to an inexpensive metastable FeMnCoCr HEA. Coupled with simple thermomechanical processing, we produced a multi-heterostructure, which consisted of fine α-martensite laths, deformed austenite with dense dislocations, recrystallized ultrafine grains and nano-nitride precipitates. Our novel FeMnCoCrN HEA exhibits a high yield strength of 1310 MPa which is ~5.2 times stronger than its base alloy without nitrogen doping. In particular, the highly dislocated body-centered cubic (bcc) martensite laths formed in the austenitic deformation matrix has an unexpected area fraction up to 24%. The hetero-deformation induced strengthening then reaches 750 MPa at the yield point, leading to a remarkable yield strength elevation of the material. Moreover, the high nitrogen content changes the dominant deformation mechanism from martensitic transformation to twinning, which contributes to a satisfactory uniform elongation of 16.5%, while the material is further strengthened by the dynamically refined microstructure. The high-nitrogen duplex alloy design strategy developed here provides a new paradigm for developing high-performance fcc HEAs.