不同表面状态和热暴露对γ-TiAl合金疲劳性能的影响

发布时间：2018-03-13 15:23

本文选题：疲劳　切入点：γ-TiAl基金属间化合物合金　出处：《稀有金属材料与工程》2017年02期 　论文类型：期刊论文

【摘要】：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。
[Abstract]:The fatigue properties of Ti-46Al-5Nb-lWatat (Ti-46Al-5Nb-lWatat) alloy with medium strength coarse grain were studied under different surface working conditions before and after thermal exposure. The results showed that although most of the samples were subjected to fatigue under the condition of 蟽 _ S _ max) 蟽 _ T _ (0.2) before thermal exposure, However, due to the large variation of grain size in laminates, it is easy to find local anomalies in the coarse lamellar grains and soft positions, which leads to early yield and initiation of cracks. The beneficial effect of surface processing quality on the fatigue strength of S-N is obviously smaller than that of fine-grained alloy. It is also found that the embrittlement effect caused by oxygen release and ordered phase transition during thermal exposure is not obvious. On the contrary, the fatigue properties of the alloy are increased because the samples are soaking in hot bath for a long time, which leads to the release of residual stress and the passivation of defects. The extent of the enhancement is related to the degree of improvement of the surface quality. The coarse grained alloy shows a lower notch sensitivity coefficient. The fatigue notch sensitivity coefficient of the alloy is 0.27 before thermal exposure and 0.32 after thermal exposure after the introduction of V-shaped notch.
【作者单位】：西南交通大学材料先进技术教育部重点实验室;
【基金】：国家自然科学基金(51271154,51201141)
【分类号】：TG146.23

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