Ti-6.5Al-3.5Mo-0.2Si钛合金热稳定性研究

Research on thermal stability of Ti-6.5Al-3.5Mo-0.2Si

本文对Ti-6.5Al-3.5Mo-0.2Si钛合金棒材热暴露毛坯和热暴露试样进行了室温力学性能和显微结构分析,研究了该合金热稳定性的变化规律和影响原因。室温拉伸结果表明:在500℃保温1,000小时热暴露后,合金的抗拉强度和屈服强度均提高25MPa;毛坯暴露后延伸率没有变化,试样暴露延伸率值下降1.5%;合金断面收缩率值均下降4.5%,材料的热稳定性能略有下降。热暴露后初生α相和β转变组织内的α片没有析出α2相;初生α相沿三叉晶界长大,形成凸起;β转变组织内的α片略有长大,β相减少,内部组织的变化是造成热稳定性下降主要原因;热暴露后表面氧化,氧化层厚约0.2μm,扩散层约1.0μm,整个氧影响区约1.2μm,对热稳定性影响很小。

The analysis of the organizational structures and mechanical properties at room temperature about Ti-6.5Al-3.5Mo-0.2Si titanium alloy bar, hot exposed blanks and hot exposed specimen are in this paper. Thermal stability's changing regularity and influences of the alloy are studied. Tensile test result at room temperature shows that alloy's tensile and yield strength increase 25 MPa respectively; and percentage of blank's elongtation drops slightly, percentage of specimen's elongtation falls 1.5% when they are exposed after keeping 1,000 hours at 500 ℃; percentage reduction of alloy's area falls 4.5%, and material's thermal stability drops a little. When material has been hot exposed, primary α phase and the secondary α phase slice that are formed among β phase change organization (β-PCO), doesn't precipitate α2 phase; primary α phase grows bigger and forms convex by the trifurcate grain boundary; the secondary α phase slice grows slightly, β phase lessens and the inner organizational structures change, these main reasons bring about thermal stability dropping; after hot exposing there is surface oxidation, the thickness is about 0.2 μm and diffusion layer's thickness is about 1.0 μm, the oxygen effective area is 1.2 μm, these factors' effect on thermal stability is less.