Novel as-cast HfNbTaTiAl refractory multi-principal element alloys with superior strength-ductility combination at room temperature

Refractory multi-principal element alloys (RMPEAs) have attracted much attention due to their excellent high temperature mechanical properties. However, extremely low room temperature tensile ductility hinders further engineering applications. In this work, we designed novel HfNbTaTiAl RMPEAs and studied the structureproperties relation and deformation mechanism at room temperature. Results show that the yield strength of the as-cast alloy is up to 1029 MPa and the tensile ductility at room temperature is between 17.8 % and 22.8 %. The high yield strength is mainly attributed to the solid solution strengthening effect. Cross-slip provides ultimate tensile strength while maintaining the tensile ductility. Kink bands have been observed in Al9.0Hf30.3Nb15.0Ta15.3Ti30.3 alloy, which is the main reason for its excellent tensile ductility at room temperature. Overall, this study elucidated the deformation mechanism of Al9.0Hf30.3NbxTa30.3-xTi30.3 (x = 0, 10, 15) as-cast RMPEAs at room temperature, and provides meaningful insights for developing RMPEAs with excellent strength-ductility combinations.