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. [Display omitted] •A series of Ti3V2NbAlxNiy low-density refractory multielement alloys were developed.•The alloy design ideas were combined with the criteria of high-entropy alloys and titanium alloys.•The phase diagram calculated by CALPHAD was helpful to understand the phase formation.•The specific yield strength and malleabilityof Ti3V2NbAl0.5Ni0.5 were superior to most refractory high-entropy alloys.