Microstructure and mechanical properties of Ti3V2NbAlxNiy low-density refractory multielement alloys

This study aimed to develop a novel series of low-density refractory high-entropy alloys (RHEAs) by precipitation strengthening. The design ideas of high-entropy alloys and titanium alloys were combined to develop Ti3V2NbAl0.5, Ti3V2NbNi0.5, and Ti3V2NbAl0.5Ni0.5 refractory multielement alloys. These alloys displayed low densities of 5.39, 5.83, and 5.55 g/cm3, respectively. The effects of Al and Ni addition on the microstructure and mechanical properties were investigated. Thereinto, the Ti3V2NbAl0.5 with a body-centered cubic structure had a yield strength of 760 MPa, and the compressive strain exceeded 50%. The Ti3V2NbNi0.5 alloy strengthened by large C15 Laves-phase particles in the interdendritic regions exhibited a high yield strength of 1130 MPa but with a limited compressive strain of 20%. By contrast, the Ti3V2NbAl0.5Ni0.5 alloy had a high yield strength of 1250 MPa and acceptable strain of 40%, benefiting from the precipitation of fine C14 Laves-phase particles and twined B19? martensite. Moreover, the specific yield strength (SYS) of the Ti3V2NbAl0.5Ni0.5 alloy was 223 kPa?m3kg? 1, superior to most other reported RHEAs at room temperature. It remained a high SYS of 198 and 54 kPa?m3kg? 1 at 700 and 800 ?C, respectively, which shows a superior balance between its density and mechanical properties across a wide temperature range.

Automated summary

A novel series of low-density refractory high-entropy alloys were developed through precipitation strengthening, showing superior balance between density and mechanical properties across a wide temperature range.