Abstract A single phase, face-centered-cubic (FCC) Al0.3CoCrFeNi high entropy alloy usually has low yield strength. Here, a precipitate-strengthened Al0.3CoCrFeNi has been developed, exhibiting enhanced yield strength while retaining good ductility, which is attributed to a novel microstructure comprising a finely distributed, needle-like B2 phase within the grains of the FCC matrix and a granular σ phase along the grain boundaries. Such a microstructure was obtained by a two-step heat treatment of an as-cast Al0.3CoCrFeNi, whose parameters were determined by integrating CALPHAD-based thermodynamic calculations with microstructural characterization by atom probe tomography. In situ neutron diffraction, in conjunction with crystal-plasticity finite-element simulations, has revealed the strengthening effect owing to the load partitioning between the constituent phases. This work has important implications for understanding phase stability and deformation mechanisms in multi-principal component alloys, and paves the way for developing novel microstructures in complex alloys using correlative techniques.
Last. Rajiv S. Mishra(UNT: University of North Texas)H-Index: 73
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Abstract Ultrafine grained (UFG) alloys suffer from limited strain hardening hence reduced ductility. Incorporation of deformation twinning can overcome this limitation. An Al 0.3 CoCrFeNi high-entropy alloy was thermo-mechanically processed to yield a UFG triplex microstructure (d avg : 0.71 ± 0.35 μm) with FCC, and hard B2 and sigma phases. The annealed material exhibited an exceptional strength-ductility combination with ultimate tensile strength (UTS) of ~1.1 GPa and elongation of ~25%. Furt...
#2Bharat Gwalani(UNT: University of North Texas)H-Index: 25
Last. Rajiv S. Mishra(UNT: University of North Texas)H-Index: 73
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Abstract High-entropy alloys (HEAs) can offer exceptional strain-rate sensitivity (SRS) due to high lattice-friction and strong solid-solution strengthening, and in some cases, low stacking fault energy. In this study, SRS of a single phase FCC HEA- Al0.3CoCrFeNi was investigated at two grain sizes. Due to its outstanding Hall-Petch coefficient, grain size becomes a crucial microstructural feature in determination of strength and SRS. Change in SRS due to grain refinement was derived to be inver...
Abstract Often the experimentally-observed, single-phase high entropy alloy (HEA) is the result of second-phase precipitation constrained by thermodynamic and kinetic factors. Using Al 0.3 CoCrFeNi as a candidate HEA, this paper demonstrates the strong influence of thermo-mechanical processing on the transformation pathway adopted for isothermal second-phase precipitation. A traditional thermo-mechanical processing route comprised of homogenization cold-rolling solution treatment in the single f...
Last. Peter K. Liaw(UT: University of Tennessee)H-Index: 94
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Abstract Compression experiments of the Al0.5CoCrCuFeNi high-entropy alloy (HEA) under displacement control were conducted at different temperatures ranging from 673 K to 873 K with a strain rate of 5 × 10−5/s to study its serration behavior. Samples after compression tests were investigated, using the synchrontron-diffraction technique and transmission-electron microscopy. By comparing the stress-strain curves at different temperatures, two opposite directions of serrations were observed, named...
#1Rui Feng(UT: University of Tennessee)H-Index: 14
#1Rui Feng(UT: University of Tennessee)H-Index: 14
Last. Peter K. Liaw(UT: University of Tennessee)H-Index: 94
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Abstract Light-weight high-entropy alloys (HEAs) with a vast alloy-design space have offered new avenues to explore novel low-cost, high strength-to-weight ratio structural materials. Studying their phase stability and possible transformations is critical for designing microstructures for optimal material properties. However, the complex local atomic environment of HEAs poses challenges to the fundamental understanding of phase stability and transformation behaviors. The present study investigat...
#1Yong Zhang(USTB: University of Science and Technology Beijing)H-Index: 112
#2Jun Peng Liu(USTB: University of Science and Technology Beijing)H-Index: 1
Last. Yan Li Wang(USTB: University of Science and Technology Beijing)H-Index: 1
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Abstract Serration and noise behaviors in plastically deforming solids are related to avalanches of deformation processes. In the stress-strain curves, the serration characteristics are visible as stress drops or strain jumps. In fact, similar serration characteristics are ubiquitous in many structural and functional materials, such as amorphous materials [also metallic glasses, or bulk metallic glasses (BMGs)], high-entropy alloys (HEAs), superalloys, ordered intermetallics, shape-memory alloys...
#1Haoyan Diao(UT: University of Tennessee)H-Index: 13
#2Rui Feng(UT: University of Tennessee)H-Index: 14
Last. Peter K. Liaw(UT: University of Tennessee)H-Index: 94
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Abstract High-entropy alloys (HEAs), as a new class of materials, are nearly equiatomic and multi-element systems, which can crystallize as a single phase or multi-phases. Most of the HEAs described in the literature contain multiple phases (secondary phases, nanoparticles, and so on), rather than a single solid-solution phase. Thus, it is essential to review the typical mechanical properties of both single-phase and multiphase HEAs thoroughly, with emphases on (1) the fundamental physical mecha...
#2Bernd Gludovatz(UNSW: University of New South Wales)H-Index: 36
Last. Robert O. Ritchie(University of California, Berkeley)H-Index: 132
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Abstract Near-equiatomic multi-component high-entropy alloys (HEAs) have engendered much attention of late due to the remarkable mechanical properties of some of these new metallic materials. In particular, one of the first reported HEAs, the equiatomic, single-phase, face-centered cubic (fcc) alloy CrMnFeCoNi, often termed the Cantor alloy, has been shown to display an exceptional combination of strength, ductility and fracture toughness, i.e. , damage tolerance, at room temperature, properties...
Abstract Grain refinement of Al 0.3 CoCrFeNi high entropy alloy with the fcc structure was studied focusing on the precipitation of the B2-type NiAl phase along grain boundaries. The B2-type precipitates effectively suppressed the grain growth during the recrystallization of the alloy following conventional cold rolling, resulting in an ultrafine-grained microstructure. In contrast, there was no precipitate in the single crystals. The alloys obtained by an appropriate thermomechanical treatment ...
Abstract A successful demonstration of applying integrated strengthening using Hall-Petch strengthening (grains size effect) and precipitation strengthening is shown in the fcc based high entropy alloy (HEA) Al 0.3 CoCrFeNi, leading to quantitative determinations of the Hall-Petch coefficients for both hardness and tensile yield strength, as well as the enhancements in the yield strength from two distinct types of ordered precipitates, L1 2 and B2. An excellent combination of yield strength (~ 4...
#1Ling Qiao(HIT: Harbin Institute of Technology)H-Index: 5
#2Yong Liu(HIT: Harbin Institute of Technology)H-Index: 15
Last. Jingchuan Zhu(HIT: Harbin Institute of Technology)H-Index: 22
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Abstract High-entropy alloys (HEAs) have attracted tremendous attention in various fields due to unique microstructures and many excellent properties. For particular applications, an in-depth understanding of the essence is important to further developing new HEAs with promising properties. In present paper, the recent development of HEAs was reviewed, including the phase formation and microstructures, various properties, and multi-scale modeling aided composition design. Materials informatics e...
Last. Hsuan-Teh Hu(NUU: National United University)
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Abstract null null Metal solutions, such as high- and medium-entropy alloys, exhibit extraordinary mechanical performance in comparison to regular alloys. In this study, we employ a crystal plasticity finite element model (CPFEM) to study the strengthening mechanisms of a new medium-entropy alloy, Ti65(AlCrNb)35. A 3D representative model is constructed by processing experimental results for Ti65(AlCrNb)35, such as average grain size, grain size distribution, and initial texture, using the open-...
Significant progress in many classes of materials could be made with the availability of experimentally-derived large datasets composed of atomic identities and three-dimensional coordinates. Methods for visualizing the local atomic structure, such as atom probe tomography (APT), which routinely generate datasets comprised of millions of atoms, are an important step in realizing this goal. However, state-of-the-art APT instruments generate noisy and sparse datasets that provide information about...
#1Chanho Lee(UT: University of Tennessee)H-Index: 12
#2Jamieson Brechtl(ORNL: Oak Ridge National Laboratory)H-Index: 12
Last. Peter K. Liaw(UT: University of Tennessee)H-Index: 94
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Bulk-metallic glasses (BMGs) and high-entropy alloys (HEAs) have attracted extensive attention in the field of metallic materials research for several decades due to their extraordinary properties. Many scientists and researchers have significantly contributed to developing new classes of metallic alloys, such as BMGs and HEAs, for various applications. Liaw’s group and his colleagues have focused on the fundamental understanding of unique features, structures, and properties in BMGs and HEAs as...
#1Kalyan Kumar Ray(IIT-KGP: Indian Institute of Technology Kharagpur)H-Index: 35
#1Kalyan Kumar Ray(IIT-KGP: Indian Institute of Technology Kharagpur)H-Index: 2
Last. Atri Nath(IIT-KGP: Indian Institute of Technology Kharagpur)H-Index: 2
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Abstract In this investigation synergistic assessments of fracture toughness and activation volume for plastic deformation of two typical body centered crystalline (bcc) and face centered crystalline (fcc) high entropy alloys containing Al, Cr, Co, Cu, Fe and Ni have been made by standard practices; these experiments together with the assessment of conventional mechanical properties were carried out to understand the underlying mechanisms responsible for the deformation and fracture response of ...
Abstract The non-equimolar Al-Co-Cr-Fe-Ni high-entropy alloy was fabricated by combined cable wire arc additive manufacturing (CCW-AAM). Microstructure evolution and mechanical properties of this dual-phase (FCC + ordered BCC (B2)) alloy under 600°C, 800°C and 1000°C heat treatment for 8 hours were investigated. The as-deposited alloy was composed of FeCr-rich FCC phase and AlNi-rich B2 phase. Under heat treatment at 600°C, a large number of Cr-rich σ phases precipitated in the B2 matrix and nan...
Abstract The present work reports microstructures and mechanical properties of the homogenized and cold-rolled (CoCrFeMnNi)95.2Al3.2Ti1.6 (at. %) high entropy alloy annealed at various temperatures. The material was cold-rolled and annealed in the temperature range from 600 °C to 1000 °C for 1 h. The σ phase was observed in the annealing temperature range from 600 °C to 800 °C while the B2 phase was observed in the annealing temperature range from 700 °C to 900 °C. The fully recrystallized mater...
#2Sang Hun Shim(CNU: Chungnam National University)H-Index: 3
Last. Sun Ig Hong(CNU: Chungnam National University)H-Index: 6
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Abstract Thermodynamic criteria of lattice distortion energy (△Hel) and enthalpy of mixing (△Hmix) were considered to design and estimate the initial phase formation and stability in (CoCrNi)100-x-y(AlTiZr)x(CuFeMo)y multicomponent alloy (MCA) system. This study aimed to chase a new alloy design pathway to develop superalloys by benefitting from the concept of multiphase MCAs. The non-equilibrium cast microstructure (CoC[rNi)100-x-y(AlTiZr)x(CuFeMo)y displayed a metastable dendritic structure co...
#1Rong Hu(Nanjing University of Science and Technology)H-Index: 3
#1Hu Rong(Nanjing University of Science and Technology)
Last. Gang Sha(Nanjing University of Science and Technology)H-Index: 37
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Abstract High-entropy alloys (HEAs), also called multi-principal-elements alloys, possess extraordinary mechanical properties, including high strength and hardness, thermal stability, corrosion resistance and radiation resistance, due to their unique and complex microstructures. The comprehensive understanding of their microstructures down to atomic level plays a vital role in developing HEAs, for tuning manufacturing parameters, examining their phase stabilities under severe conditions for futu...
Last. Peter K. Liaw(UT: University of Tennessee)H-Index: 94
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High-entropy alloys (HEAs) are materials that consist of equimolar or near-equimolar multiple principal components but tend to form single phases, which is a new research topic in the field of metallurgy, have attracted extensive attention in the past decade. The HEAs families contain the face-centered-cubic (fcc), body-centered-cubic (bcc), and hexagonal-close-packed (hcp)-structured HEAs. On one hand, mechanical properties, e.g. hardness, strength, ductility, fatigue, and elastic moduli, are e...