Influence of solution treatment on microstructure and mechanical properties of a near β titanium alloy Ti-7333

摘要

The effect of solution treatment on the microstructure and mechanical properties of Ti-7333, a newly developed near β titanium alloy, was investigated. Compared to Ti-5553 and Ti-1023, Ti-7333 possesses the slowest α to β dissolution rate, allowing a wider temperature window for processing. The rate of β grain growth decreases with the increase of soaking time and increases with the increase of solution temperature. The β grain growth exponents (n) are 0.30, 0.31, 0.32 and 0.33 for solution treatment temperature of 860 ℃, 910 ℃, 960 ℃ and 1010 ℃, respectively. The activation energy (Q_g) for β grain growth is 395.6 kJ/mol. Water cooling or air cooling after solution treatment have no significant influence on microstructure, which offers large heat treatment cooling window. However, under furnace cooling, the fraction of α phase increases sharply. α phase maintains strictly the Burgers orientation relation with β phase ({0001}_α//{110}_β and <11-20>_α//<111>_β), except the α_p particles formed during forging. The tensile strength decreases with the increase of the solution temperature when only solution treatment is applied, whereas the ductility increases gradually. When aging is applied subsequently, the tensile strength increases with the increase of the solution temperature and the ductility decreases gradually.