Effect of Ti on microstructure and mechanical properties of Al0.8Nb0.5TixV2Zr0.5 refractory complex concentrated alloys

Abstract

In this study, lightweight Al0.8Nb0.5TixV2Zr0.5 refractory complex concentrated alloys with different Ti contents (x = 0.4, 0.8, 1.2, and 1.6) are fabricated via vacuum arc melting. The effects of Ti on microstructurale evolution, density, and mechanical properties at room and elevated temperatures are investigated. The Al0.8Nb0.5TixV2Zr0.5 alloys are composed of a BCC solid solution matrix and a C14-Laves (hexagonal) phase, and the volume fraction of the BCC phase increases as the Ti content increases from 63.48% to 90.97%. The density decreases from 5.70 to 5.42 g/cm3, whereas the hardness first increases and then decreases in the range of 625.2 to 669.5 HV. The results of compression test at different temperatures show that the yield strength and deformability of the Al0.8Nb0.5TixV2Zr0.5 alloys first increases and then decreases, and that the alloys show good phase stability when the Ti content is 1.2. The compressive yield strength of Ti1.2 alloy is 1848 MPa at room temperature, 1507 MPa at 673 K, and 1068 MPa at 1073 K. The increase in yield strength is due to various strengthening mechanisms caused by the addition of Ti, including the solid-solution strengthening effect caused by severe lattice distortion, the decrease in the valence electron concentration, and the grain boundary strengthening effect caused by grain size reduction. The present study is an example of a systematic investigation into the effects of elements on the structure and properties of refractory complex concentrated alloys through alloy design, which is expected to facilitate the design of lightweight refractories and their compositions.