Formation of coherent BCC/B2 microstructure and mechanical properties of Al–Ti–Zr–Nb–Ta–Cr/Mo light‐weight refractory high‐entropy alloys
Dongming Jin, Zhenhua Wang, Jinfeng Li, Ben Niu, Qing Wang
Abstract
Abstract The present work investigated the formation of coherent body‐centered‐cubic (BCC)/B2 microstructure in Al–Ti–Zr–Nb–Ta–Cr/Mo refractory high‐entropy alloy system, in which three alloys with the composition of Al 2 Ti 6 Zr 2 Nb 3 Ta 2 (Cr/Mo) 1 were designed. These as‐cast alloy ingots were homogenized at 1573 K for 2 h and then aged at different temperatures for 24 h. It is found that the BCC/B2 coherent microstructure with cuboidal BCC nanoprecipitates into the B2 matrix would be formed in 873 K‐aged Al 2 Ti 6 Zr 2 Nb 3 Ta 2 Cr 0.5 Mo 0.5 alloy with half Cr and half Mo, which is ascribed to a moderate lattice misfit ( ε = 0.94%) between BCC and B2 phases. It is due to the special coherent microstructure that results in a prominent mechanical property with the highest compressive yield strength ( σ YS = 1314 MPa) and good plasticity among these alloys, while coarse Cr 2 Ti and Zr 5 Al 3 particles are existed in 873 K‐aged alloy with Cr 1 . After 1073 K aging, all these alloys with Cr 1 , Cr 0.5 Mo 0.5 and Mo 1 consist of BCC, B2 and Zr 5 Al 3 , in which BCC/B2 coherent microstructure is destabilized. The strengthening mechanism of BCC/B2 coherent microstructure in 873 K‐aged alloy with Cr 0.5 Mo 0.5 was also discussed.