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研究了全片层组织的中等强度γ-TiAl合金Ti-45Al-2Mn-2Nb-0.8TiB2在热暴露+表面氧化10000 h以后,4种加工表面与高频疲劳行为的定量关系。结果表明:在该TiAl合金的疲劳过程中当经历长时间热暴露+氧化后,相对于热暴露之前,该合金的疲劳强度有增有降,依表面加工方式而定。表面质量差的线切割样品以及表面无压应力的电解抛光样品,出现“热暴露+氧化增强”的现象,这表明大气热暴露导致的应力弛豫现象带来的有利效果大于表层氧化产生的不利效果。热暴露+氧化对喷丸样品有明显不利效果,热暴露引起的应力弛豫导致喷丸样品表面压应力降低,层厚减薄,氧化引起表面疏松,引入了缺陷。
The quantitative relationship between four processing surfaces and high frequency fatigue behavior of Ti-45Al-2Mn-2Nb-0.8TiB2, a fully textured γ-TiAl alloy, after heat exposure + surface oxidation for 10000 h was studied. The results show that the fatigue strength of the TiAl alloy increases or decreases as compared with that before heat exposure after prolonged thermal exposure and oxidation during the fatigue of the TiAl alloy, depending on the surface processing method. The phenomenon of “thermal exposure + oxidation enhancement” appeared in the samples with poor surface quality and the electro-polished samples with no compressive stress on the surface, indicating that the beneficial effect of the stress relaxation caused by atmospheric heat exposure is greater than the surface oxidation Adverse effects. Thermal exposure and oxidation have obvious adverse effects on shot peening samples. The stress relaxation caused by thermal exposure leads to the decrease of compressive stress on the surface of shot peening samples, the thinning of layer thickness, the oxidation caused surface looseness and the introduction of defects.