热暴露对TiAl合金室温拉伸性能影响的研究进展

室温拉伸塑性是TiAl合金这类低损伤容限材料工程化应用必须考虑的重要指标之一。高温热暴露后TiAl合金的室温塑性显著降低,这不利于TiAl合金部件的应用可靠性。概述了高温热暴露对TiAl合金室温拉伸性能特别是室温拉伸塑性的影响,重点归纳了高温热暴露造成的表面性质变化对该合金室温塑性不利影响的可能机制,并提出了抑制热暴露所致室温塑性降低的可能途径。分析表明,热暴露导致TiAl合金室温拉伸塑性降低,是表面氧化致脆、表面残余应力以及环境潮气等因素综合作用的结果,其中表面氧化致脆是直接原因。改善基体的抗氧化性或者形成可抑制表面裂纹向基体扩展的有利组织,是保持TiAl合金高温使用后室温拉塑性水平的有效途径。

Research Development in Effect of Thermal Exposure on Tensile Ductility of Gamma TiAl Based Alloys at Room Temperature

Tensile ductility at room temperature was one of mechanical properties mainly considered in engineering application for TiAl alloy with low damage tolerance. However, tensile ductility of TiAl alloy significantly reduced after thermal exposure, which would bring an adverse effect on application reliability of TiAl components. This paper summarized the influence of thermal exposure on tensile properties at room temperature of gamma titanium aluminide alloys, in which tensile ductility was mainly focused. Meanwhile, the mechanisms of embrittlement induced by change on the surface during thermal exposure were detailed analyzed. And then possible approaches were proposed to restrain embrittlement induced by thermal exposure. The results showed that reduction of tensile ductility induced by thermal exposure for TiAl alloys was attributed to the combination effect of surface oxidation, surface residual stress and atmospheric moisture, of which oxidation on the surface was the direct cause. Improving the oxidation resistance of the materials would be helpful for reducing the embrittlement induced by thermal exposure. And forming a beneficial structure inhibiting surface crack growing into the substrate would further reduce the embrittlement induced by thermal exposure.