Enhanced yielding strength of near-α Ti-Al-Zr-Sn high temperature alloys

The effect of Si3N4 addition on the mechanical properties and microstructure of Ti-Al-Zr-Sn based near-α Ti alloys has been systematically investigated at both room temperature and high temperature (650 °C). Minor Mo and Ta (β stabilizing elements) together with Si3N4 addition have significantly improved the compressive yielding strength at both room temperature and 650 °C. The strengthening effect was mainly due to the precipitation of TiN, α2-Ti3Al and the retained β phase. High compressive yielding strength together with pronounced ductility can be obtained by only adding minor Si3N4 into Ti-Al-Zr-Sn alloys. The enhanced ductility is probably due to the depression of the brittle α2 intermetallic phase, which did not precipitate out even after long time ageing (750 °C for 500 h).