Super tensile ductility in an as-cast TiVNbTa refractory high-entropy alloy

Refractory high-entropy alloy (RHEA) usually exhibits a high melting point and hence a very high deformation resistance at high temperatures. However, the relatively poor plasticity at room temperature, i.e., only few RHEAs displaying as-cast tensile ductility, strongly limits the applications of RHEAs as engineering materials. In this work, we show a huge tensile ductility observed in an as-cast TiVNbTa RHEA (-40 % fracture elongation) accompanying with a high yield strength (-800 MPa), which are rarely reported properties for RHEAs. The as- cast alloy shows a simple body-centered cubic (BCC) structure with dendrites. Ductile fracture with many dimples is the main fracture mechanism, while no twinning and deformation induced phase transition was observed. The uniform plastic deformation mainly relies on the planar and cross-slip of dislocations. The present result suggests the huge ductility potentials for RHEAs, providing a clue for designs future high performance RHEAs with good ductility.