Effect of Zr on the as-cast microstructure and mechanical properties of lightweight Ti2VNbMoZrx refractory high-entropy alloys

Refractory high-entropy alloys (RHEAs) have attracted extensive attention due to their outstanding hightemperature performance. However, high density and poor ductility are the two bottleneck problems in industrial application. This study aims to exploit novel RHEAs with high specific strength and good ductility by adding light Group IVB elements. The effect of Zr on the as-cast microstructure, density, and mechanical properties of Ti2VNbMoZrx (x = 1, 1.5, 2, and 3) RHEAs was investigated in detail. All Ti2VNbMoZrx RHEAs exhibited a disordered body-centered-cubic solid-solution phase. The as-cast microstructures changed from dendritic morphology (x =1 and 1.5) to equiaxed dendritic morphology grain (x = 2 and 3) with the increasing Zr content. The Ti2VNbMoZr2 RHEA displayed optimal mechanical properties with a compressive yield strength of 1421 MPa, a plastic strain of 31.6%, and a specific yield strength of 211 kPa center dot m3 center dot kg-1, superior to the most-reported RHEAs. The microbands along {110} and {112} slip planes, which was a typical poly slip configuration, were observed in the Ti2VNbMoZr2 alloy after compression test using ex-situ transmission electron microscopy. Furthermore, the Ti2VNbMoZr2 RHEA exhibited good high-temperature mechanical properties, showing a yield strength of 977 MPa at 600 degrees C and 386 MPa at 800 degrees C without fracture at a plastic strain of 50%. The solution strengthening model revealed that the high yield strength of Ti2VNbMoZrx RHEAs was mainly derived from the atomic radius misfit and shear modulus misfit of the Zr atoms.

Automated summary

Refractory high-entropy alloys (RHEAs) have attracted attention for their high-temperature performance, but high density and poor ductility are issues. This study investigated Ti2VNbMoZrx RHEAs and found that Ti2VNbMoZr2 alloy displayed optimal mechanical properties, with high compressive yield strength and plastic strain, as well as excellent high-temperature performance. Solution strengthening model showed that Zr atoms contributed to the high yield strength of Ti2VNbMoZrx RHEAs.