Microstructure and mechanical properties of novel β-type Ti–Co–Zr alloys with high specific strength

Abstract

Microstructure and mechanical properties of (Ti0.8Co0.2)100−xZrx (x = 0, 2, 4, 6 and 8 at%) alloys were investigated. The content of Ti2Co phase decreases with the content of Zr and then increases. The Ti–Co–Zr alloys are composed of eutectic structure of Ti2Co and Ti phase, and the Ti75.2Co18.8Zr6 and Ti73.6Co18.4Zr8 alloys with the particle sizes of less than 10 μm are the microcrystalline alloy. The high yield strength of Ti75.2Co18.8Zr6 and Ti73.6Co18.4Zr8 alloys with high Vickers hardness are attributed to the refinement of the β-Ti phase; the Ti78.4Co19.6Zr2 alloy has high specific compression strength; the specific strength of Ti–Co–Zr alloys are more than 300 Pa · m3 · g−1. Based on the nanoindentation, the range of reduced elastic modulus (Er) and hardness (H) are from 89.6 GPa to 114.6 GPa, from 4.39 GPa to 6.28 GPa, respectively. The H/Er values of five Ti–Co–Zr alloys are higher than that of the CP–Ti (0.0238) alloy, suggesting that the novel Ti–Co–Zr alloys show good wear resistance. In addition, the Ti78.4Co19.6Zr2 and Ti73.6Co18.4Zr8 alloys have good elastic recovery (Ue/Ut), however, the Ti80Co20 and Ti75.2Co18.8Zr6 alloys have good intrinsic plasticity (Up/Ut) in the present Ti–Co–Zr alloys.