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研究了中等强度粗晶粒γ-TiAl合金Ti-46Al-5Nb-lW(at%)热暴露前、后不同表面加工状态下的疲劳性能。结果表明,热暴露前虽然绝大多数样品在σ_(max)<σ_(0.2)的条件下进行疲劳,但是由于层片晶粒尺寸变化幅度大,容易在粗大的层片晶粒和软位向上,出现σ_(max)>σ_(0.2)的局部异常情况,导致早期屈服并诱发裂纹萌生。因此,表面加工质量的改善对S-N疲劳强度的有益影响明显小于细晶粒合金。研宄还发现,热暴露中由于释氧和有序相相变引起的脆化效应并不明显,合金反而因样品在热浴中长期浸泡,导致残余应力释放和缺陷钝化而出现了疲劳性能增强的趋势。其增强的幅度和表面质量改善的程度相关。此外,该粗晶粒合金显示出较低的缺口敏感系数,在引入V型缺口后,其疲劳缺口敏感系数在热暴露前为0.27,热暴露后为0.32。
The fatigue behavior of medium-strength coarse grain γ-TiAl alloy Ti-46Al-5Nb-lW (at%) under different surface processing conditions before and after heat exposure was studied. The results show that most of the samples before thermal exposure show fatigue at σ max (σ 0.2). However, due to the large variation of grain size, , A local anomaly of σ_ (max)> σ_ (0.2) appears, resulting in early yielding and inducing crack initiation. Therefore, the beneficial effect of the improvement of surface quality on S-N fatigue strength is obviously less than that of fine grain alloy. Research also found that heat exposure due to oxygen and ordered phase transition caused by embrittlement effect is not obvious, but due to the alloy sample immersed in the hot bath for a long time, leading to the release of residual stress and defects passivation and fatigue performance Increased trend. The magnitude of this enhancement is related to the degree of surface quality improvement. In addition, the coarse-grained alloy showed a lower notch sensitivity coefficient. After introducing V-notch, the fatigue notch sensitivity coefficient was 0.27 before thermal exposure and 0.32 after thermal exposure.