Phase transformation and dislocation behavior dependence on cooling rate in novel refractory high entropy alloy

A newly named “NbSi-containing refractory high-entropy alloy (RHEA)” is proposed using the Nb–Si based alloy insight. Light-weight TiNbMo_0.5Al_0.225Si_x RHEAs were designed (6–6.67 g/cm³), then we studied the dependence of cooling rates on the phase transformation, and the deformation mechanism at the room, high temperatures. Two portions of phase transitions were observed, β-(Nb, Ti)₅Si₃ to γ-(Nb, Ti)₅Si₃, and BCC solid solution (BCCss) to γ’-(Nb, Ti)₅Si₃ precipitates. Elemental diffusion drives the splitting of the grain boundary grooving into sub-boundary, accompanied by phase transformation that occurs. An appropriate Si content favors an excellent strength-plasticity synergy, resulting in 1763.58 MPa compressive strength and 23.65% compressive strain at room temperature (RT), also exhibiting superior yield strength of 1444.82 MPa and relevant strain of 17.48% at elevated temperature (800 °C). The high-temperature dislocation behavior of quenched alloy, evolves from cross-slip (as-cast alloy) to climb-slip coupled deformation mechanism, which plays a crucial role in homogeneous plastic deformation. Therefore, the current work having designed novel alloys sheds new light on designing nanoprecipitates and diversifying dislocation modes.