材料期刊网

利用透射电镜方法对500℃长时间热暴露的TC9合金的观察结果表明:热暴露导致残留β相分解析出次生α相和原有的次生α相长大。观察到1型和2型两种次生α相。此外,热暴露还导致Ti_3Al相从初生α相内析出并弥散地分布。延长热暴露时间促使Ti_3Al相颗粒数量增加。在初生α相内析出Ti_3Al相是此合金热暴露致脆的内部组织原因。分析实验结果得出Ti_3Al相与α相的取向关系为(0001)α∥(0001)Ti_3Al,<(?)0>α∥[2(?)]Ti_3Al。

The microstructural change of TC9 Ti-alloy(Ti-6.5Al-3.5Mo-2.SSn-0.3Si)during 500℃ long-term exposure has been investigated by TEM. Such phase changes in the alloy on exposure have been observed that the Ti_3Al phase precipitates and disperses in primary a-phase; and the retained β-phase decomposes to cause the precipitation of secondary a-phase and the growth of original secondary a-phase, and the existence of type 1 and 2 of the secondary a-phase is confirmed. As the exposure prolonged, the Ti_3Al phase may gradually be increased and grew up. It is suggested that the precipitation of Ti_3Al in primary a-phase may embrittle the alloy during 500℃ exposure. Experiments identified that the orientation relation ship between Ti_3Al and a-phase is (0001)_a//(0001)_(Ti_3Al) and <2(?)0>_a//[2(?)0]_(Ti_3Al).