Creep behavior of a precipitation-strengthened A2-B2 refractory high entropy alloy
Yang Liu, Sandipan Sen, Daniel Schliephake, R.J. Vikram, Stephan Laube, Aparajita Pramanik, Ankur Chauhan, Steffen Neumeier, Martin Heilmaier, Alexander Kauffmann
Abstract
Refractory compositionally complex alloys consisting of a disordered A2 matrix and ordered B2 precipitates mimic the microstructures of state-of-the-art, Ni-based superalloys with A1 matrix and L1 2 precipitates. The former are promising candidates for high-temperature applications because of their high melting points. 27.3Ta-27.3Mo-27.3Ti-8Cr-10Al (in at. %, TMT-8Cr-10Al) is a relevant example where this A2-B2, two-phase microstructure is formed by a precipitation reaction and remains stable even at temperatures close to the precipitate solvus temperature ( T S ). The present study systematically addresses the creep response of polycrystalline TMT-8Cr-10Al at temperatures of 1000 °C and above. Compared to polycrystalline, single-phase A2 and B2 high entropy alloys, a substantially higher compression creep resistance is observed for the two-phase alloy while minimum creep rates comparable to those of state-of-the-art single-crystalline A1-L1 2 CMSX-4 are found. This is specifically remarkable considering the polycrystalline condition of TMT-8Cr-10Al, the open matrix A2 crystal structure and the close proximity of the test temperatures to the solvus temperature with 0.98 T S compared to 0.85 T S for CMSX-4. Consistent with a positive lattice misfit, directional coarsening of precipitates in TMT-8Cr-10Al is noted to be perpendicular to the compression direction after creep in grains with 〈 100 〉 close to the compression direction.