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

The effect of solution treatment on the microstructure and mechanical properties of Ti-7333, a newly developed near beta titanium alloy, was investigated. Compared to Ti-5553 and Ti-1023, Ti-7333 possesses the slowest alpha to beta dissolution rate, allowing a wider temperature window for processing. The rate of beta grain growth decreases with the increase of soaking time and increases with the increase of solution temperature. The beta grain growth exponents (n) are 0.30, 0.31, 0.32 and 0.33 for solution treatment temperature of 860 degrees C, 910 degrees C, 960 degrees C and 1010 degrees C, respectively. The activation energy (Q(g)) for beta 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 alpha phase increases sharply. a phase maintains strictly the Burgers orientation relation with beta phase ((0001)(alpha)//{110)(beta) and < 11-20 >(alpha)//< 111 >(beta), except the alpha(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. (C) 2015 Elsevier Ltd. All rights reserved.