基于小冲杆试验的TC4氢脆行为和机理研究

Hydrogen embrittlement behavior and mechanisms of Ti-6Al-4V alloy based on small punch test

摘要:

Ti-6Al-4V合金(TC4)广泛应用于海洋和航空领域，其恶劣的使用环境容易引发氢脆(HE)失效而使得TC4的机械性能退化，导致突然的灾难性断裂。为了研究TC4合金的氢脆行为和机理，首先采用小冲孔试验(SPT)测试了TC4合金在不同充氢时间下的力学性能。然后利用原子力显微镜(AFM)和X射线衍射(XRD)技术对TC4合金在不同充氢时间下的氢分布和相转变进行了详细的研究。小冲杆试验（SPT）拟合数据显示，随着充氢时间的增加，TC4合金的强度和伸长率均发生明显的劣化，同时其宏观断口形态由韧性向脆性转变。与此同时，研究还证明了电解充氢后氢化物的生成是导致TC4合金氢脆现象产生的主要原因。本文的研究结果为在役TC4设备的氢脆性能检测提供了一种有效、简便的方法。

Abstract:

Ti-6Al-4V alloy (TC4) is widely used in the field of marine and aviation, and its severe service environment is easy to lead to hydrogen embrittlement (HE) which can cause the degradation of mechanical properties and a sudden catastrophic fracture for the material. To investigate the HE behavior and mechanisms, mechanical properties of the TC4 alloy after different electrochemical hydrogen charging (EHC) time were measured by small punch test (SPT) first. Then, hydrogen distribution and the phase transition of the TC4 alloy with different EHC time were discussed in detail based on the atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The strength and elongation obtained by SPT fitting data show obvious deterioration with increasing EHC time while the macroscopic fracture morphology of the TC4 alloy exhibits a transformation from ductile mode to brittle mode. At the same time, the generation of hydride after EHC is proved a main contributor to the HE of the TC4 alloy. The results in this paper provide an effective and convenient method to assess the HE behavior of TC4 alloy in service.