喷丸强化对TC4钛合金表面完整性及疲劳性能的影响

摘要

In order to study the effects of shot peening on the surface integrity and fatigue properties of titanium alloy, we study the surface morphology, surface roughness, surface metallography, surface micro-hardness and surface residual stress of shot peened TC4 titanium alloy by using a scanning electron microscopy （ SEM）, surface profile gauge, metallography microscopy, micro-hardness instrument and X-ray diffraction residual stress analyzer, etc. The fatigue resistance of titanium alloy is investigated by using microcomputer-controlled and high-frequency fatigue testing machine. The relationship between surface integrity and fatigue resistance is discussed. The investi- gation results show that the tension-tension fatigue resistance of TC4 titanium alloy can he greatly improved by reasonable shot peening. The fatigue limit improves by about 14.5% with the shot peening, including 0.10 mmA 0.15 mmA intensity and 100% coverage. However, the fatigue resistance of TC4 titanium alloy can not be significantly improved with the higher shot peening intensity of 0.15 mmA -0.20 mmA. The effect of shot peening on the fatigue property of TC4 titanium alloy is due to the effect of shot peening on its surface integrity. The fatigue resistance of TC4 titanium alloy improves significantly when the surface residual compressive stress and structural strengthening factors induced by shot peening are dominant.%为了探讨喷丸强化对钛合金表面完整性及其疲劳行为的影响规律,采用扫描电子显微镜（SEM）、表面粗糙度仪、金相显微镜、显微硬度计及X射线应力测试仪等,分析了喷丸处理的TC4钛合金表面形态特征、表面粗糙度、表层金相组织、表层硬度以及表层残余应力分布,采用微机控制高频疲劳试验机评价了喷丸强化对TC4钛合金疲劳抗力的影响,探讨了喷丸试样表面完整性与疲劳抗力的内在联系及作用机制。结果表明：采用合理的喷丸强化工艺能够显著提高TC4钛合金的拉-拉疲劳抗力,以强度0.10 mmA～0.15 mmA、覆盖率100%的条件喷丸处理TC4钛合金,能够使其疲劳极限提高14.5%。然而,过高强度（0.15 mmA～0.20 mmA）的喷丸处理,并不能达到显著提高TC4钛合金疲劳抗力的目的。喷丸强化对TC4钛合金疲劳行为的影响归于喷丸对其表面完整性的影响,当喷丸引入的表面残余压应力及组织强化因素为主导时,钛合金疲劳抗力能够得到显著地提高。