对TiAl合金的标准拉伸试样分别进行700℃×100h和750℃×100h的热暴露处理,观察表明,机械抛光试样的表面具有规则的抛光痕迹,经700℃×100h热暴露后试样表面生成絮状氧化物,表面仍可见机械抛光痕迹.而经750℃×100h热暴露后,试样表面生成较厚的、均匀分布的氧化层,该氧化层的显微硬度显著高于基体的显微硬度.由于合金的层片组织存在取向性,因而在氧化层与基体之间存在富铝的过渡层,有利于阻止基体的进一步氧化.测试结果表明热暴露在一定程度上降低了原抛光试样表面的残余压应力水平.拉伸结果表明,热暴露后试样的室温拉伸塑性普遍明显下降.分析认为,热暴露后合金塑性的下降主要归因于试样表面残余压应力水平的降低而弱化了表面压应力对拉伸中表面裂纹萌生的抑制作用,750℃×100h热暴露试样承载能力的明显降低与拉伸中氧化层与基体的界面处出现的连续裂纹有关.
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