Solidification segregation-driven microstructural evolution of trace yttrium-alloyed TaMoNbZrTiAl refractory high entropy alloys

Here we employ the rare-earth element alloying strategy for microstructure and mechanical property tuning of a TaMo_0.5NbZrTi_1.5Al_0.1 refractory high entropy alloy (RHEA). The alloying of 0.4 at.% Y intensifies solidification segregation, with the enrichments of Zr and Al in the interdendritic region. The severer solidification segregation in the Y-alloyed RHEA drives the microstructural evolution upon annealing for the Y-alloyed RHEA, including the significant grain refinement, the removal of residual oxygen and the reduced nano-sized precipitates. However, the Y₂O₃ oxides and shrinkage defects are also generated in Y-alloyed RHEA. Compressive mechanical testing verifies the slight beneficial effect of the alloying of trace Y on the compressive strength (up to ∼1669 MPa) and fracture strain (up to ∼20.6%) of RHEA with an intergranular fracture mode. This work provides a primary exploration on RHEAs modified by rare-earth elements, and can be used as a reference for future alloy design.