Design of Motavw Refractory High-Entropy Alloys with Superior Mechanical Properties

Abstract

Combining high strength and good ductility is an urgent requirement for refractory high entropy alloys (RHEAs), but yet a challenge. Here, we designed and successfully developed a novel MoTaVW RHEAs with excellent strength and ductility. The phase composition, microstructure, mechanical properties, strengthening and deformation mechanism were studied and analyzed in depth, respectively. Different from other RHEAs with few phases, MoTaVW RHEA contains three phases (Ta-rich, Mo-rich and V-rich phase) with different composition differences at low temperatures. With the increase of sintering temperature, the single BCC solid solution phase with uniform element distribution and higher solid solubility was gradually formed. The yield strength (σy) and plastic strain (εp) reach the maximum value of 1578 MPa and 20% at 1700°C, which achieved good combination of high strength and high plasticity compared with other most known BCC RHEAs. The high yield strength of the MoTaVW RHEA was mainly due to the high solid solution strengthening caused by lattice distortion. The Ta-rich phase with more slip directions in MoTaVW RHEA further improves the plasticity by increasing the proliferation ability of dislocations. The combination of hard phase (matrix phase and Mo-rich phase) and soft phase (Tarich phase) in MoTaVW RHEA greatly achieves simultaneous improvement of strength and plasticity.

Keywords: MoTaVW, refractory high-entropy alloys, strength, ductile