Microstructure and small-scale size effects in plasticity of individual phases of Al0.7CoCrFeNi High Entropy alloy

Giwa, Adenike M.; Liaw, Peter K.; Dahmen, Karin A.; Greer, Julia R.

doi:10.1016/j.eml.2016.04.013

Cited by 51 publications

(21 citation statements)

References 36 publications

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“…Mechanical properties in CSAs have been studied at macro-and micro-scopic levels, 48,49 but deformation analysis is key to establish high-T structural candidates. We perform quasi-static uniaxial loading via MD simulations (see Methods) by deforming an ideal single-crystal alloy in small but finite steps and equilibrating after each step.…”

Section: Deformation Analysismentioning

confidence: 99%

Design of high-strength refractory complex solid-solution alloys

et al. 2018

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Nickel-based superalloys and near-equiatomic high-entropy alloys containing molybdenum are known for higher temperature strength and corrosion resistance. Yet, complex solid-solution alloys offer a huge design space to tune for optimal properties at slightly reduced entropy. For refractory Mo-W-Ta-Ti-Zr, we showcase KKR electronic structure methods via the coherent-potential approximation to identify alloys over five-dimensional design space with improved mechanical properties and necessary global (formation enthalpy) and local (short-range order) stability. Deformation is modeled with classical molecular dynamic simulations, validated from our first-principle data. We predict complex solid-solution alloys of improved stability with greatly enhanced modulus of elasticity (3× at 300 K) over near-equiatomic cases, as validated experimentally, and with higher moduli above 500 K over commercial alloys (2.3× at 2000 K). We also show that optimal complex solid-solution alloys are not described well by classical potentials due to critical electronic effects.

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Section: Deformation Analysismentioning

confidence: 99%

Design of high-strength refractory complex solid-solution alloys

et al. 2018

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“…Different from the relatively uniform lattice structure in the pure metals, the structure of HEAs usually comes with a severe lattice distortion when the constituent elements keep their original size and are forced to be incorporated into a lattice 98. High entropy effect of HEAs can stabilize the phase structure by lattice distortion 99. Generally, atomic size difference (δ) is expressed as follows82

δ = \sqrt{\sum_{i = 1}^{n} c_{i} {(1 - \frac{r_{i}}{\bar{r}})}^{2}}, \bar{r} = \sum_{i = 1}^{n} c_{i} r_{i}

here, c i and r i are the atomic percentage and the atomic radius of the i th atom, respectively.…”

Section: Phase Engineering Of Heasmentioning

confidence: 99%

Phase Engineering of High‐Entropy Alloys

et al. 2020

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High‐entropy alloys (HEAs) are based on five or more principal elements with equal or nearly equal molar fractions and possess many significant advantages over traditional alloys, including high strength and hardness, excellent corrosion resistance, outstanding thermal stability, and irradiation resistance. Phase structure plays a vital role in determining the property of HEAs. For further enhancing the performance of HEAs in various application fields, a controllable synthesis with desired phases is required. In this review, the diverse phase structures of HEAs and the related properties are first introduced. Then, alternative tuning strategies to promote the desired phase structure of HEAs are focused upon. Property adjusting of phase‐engineered HEAs is also discussed in depth. Lastly, some insights into the challenges and future prospects in this rapidly emerging research field are provided.

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“…The pillars fabricated on B2 and L1 2 phases had different orientation and yield strength changes with grain orientation. Therefore, the critical resolved shear stress (CRSS) was calculated for each phase using Schmid factor [41][42][43] to account for the crystal orientation. The slip system with maximum Schmid factor for B2 phase was (121) [11 1] and for L1 2 phase were two, namely (111)[01 1] and (11 1)[011].…”

Section: Small-scale Mechanical Behavior By Nano-indentationmentioning

confidence: 99%

Small-scale mechanical behavior of a eutectic high entropy alloy

Muskeri

Hasannaeimi

Salloom

et al. 2020

Sci Rep

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eutectic high entropy alloys, with lamellar arrangement of solid solution phases, represent a new paradigm for simultaneously achieving high strength and ductility, thereby circumventing this wellknown trade-off in conventional alloys. However, dynamic strengthening mechanisms and phaseboundary interactions during external loading remain unclear for these eutectic systems. In this study, small-scale mechanical behavior was evaluated for Alcocrfeni 2.1 eutectic high entropy alloy, consisting of a lamellar arrangement of L1 2 and B2 solid-solution phases. The ultimate tensile strength was 1165 MPa with ductility of ~18% and ultimate compressive strength was 1863 MPa with a total compressive fracture strain of ~34%. Dual mode fracture was observed with ductile failure for L1 2 phase and brittle mode for B2 phase. Phase-specific mechanical tests using nano-indentation and micro-pillar compression showed higher hardness and strength and larger strain rate sensitivity for B2 compared with L1 2. Micro-pillars on B2 phase deformed by plastic barreling while L1 2 micro-pillars showed high density of slip steps due to activation of more slip systems and homogenous plastic flow. Mixed micropillars containing both the phases exhibited dual yielding behavior while the interface between L1 2 and B2 was well preserved without any sign of separation or cracking. Phase-specific friction analysis revealed higher coefficient of friction for B2 compared to L1 2. These results will pave the way for fundamental understanding of phase-specific contribution to bulk mechanical response of concentrated alloys and help in designing structural materials with high fracture toughness. Multi-principal element alloys (MPEAs), also known as high entropy alloys (HEAs), offer a new paradigm in structural alloy design and development owing to their appealing physical and mechanical properties such as high fracture toughness, good wear and fatigue resistance, high strength and good elevated temperature properties 1-3. Several HEA systems have been reported with a single-phase face center cubic (FCC) or body center cubic (BCC) structure 4-6. To concurrently achieve good ductility of FCC HEAs along with high strength of BCC HEAs, eutectic high entropy alloys (EHEAs) have recently been developed to overcome the limitations of single-phase HEAs 7. EHEAs typically consist of a mixture of two solid-solution phases in the form of lamellae or rod-like dispersions in a matrix. To date, several EHEAs have been reported with excellent combination of high strength and ductility including CoFeNi 1.

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Microstructure and small-scale size effects in plasticity of individual phases of Al0.7CoCrFeNi High Entropy alloy

Cited by 51 publications

References 36 publications

Design of high-strength refractory complex solid-solution alloys

Design of high-strength refractory complex solid-solution alloys

Phase Engineering of High‐Entropy Alloys

Small-scale mechanical behavior of a eutectic high entropy alloy

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