Design of high-strength refractory complex solid-solution alloys

Abstract

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.

On the electronic structure and hydrogen evolution reaction activity of platinum group metal-based high-entropy-alloy nanoparticles

“…11 Löffler et al found that Cr-Mn-Fe-Co-Ni complex solid solution showed at least comparable catalytic activity to Pt in oxygen reduction reaction (ORR), in despite that none of its constituents had good ORR activity. 12 In addition to HEA, other alternative denominations have also been discussed elsewhere, such as complex solid solutions, [12][13][14] multiprincipal element alloys, 15 polyelemental particles, 16,17 multi-elemental alloy, 18 and multimetallic clusters/particles. 19 These kinds of alloys may present a class of promising ideal catalysts having desired activity, stability and selectivity and thus make a paradigm shi in catalysis research.…”

Al-Ti-Containing Lightweight High-Entropy Alloys for Intermediate Temperature Applications

“…The empirical parameters for the HEAs originated from the classic Hume-Rothery rules [22,23]. Guo et al [24] reported that −22 ≤ ΔHmix ≤ 7 kJ/mol, and δ ≤ 8.5% are required for the sole simple phases (i.e., FCC, BCC, and their mixtures, including both ordered/disordered cases).…”

Tuning phase stability and short-range order through Al doping in (CoCrFeMn)100−xAlx high-entropy alloys

“…To best of our knowledge, in solid solution forming HEAs, there are no exceptions to the trend that a higher VEC favors the FCC phase and a lower VEC favors the BCC phase. This can be justified as follows: BCC forms for 4<VEC<6 [3,31], as stability increases when bonding d-states fill and maximal when half-filled (VEC~6); anti-bonding states fill roughly when VEC>6 and stability decreases. For 6.8<VEC<8 other phases compete (e.g., s phase), and FCC become stable for VEC>8 [3,31].…”