钛合金Ti6Al4V螺钉断裂原因分析

针对钛合金Ti6Al4V螺钉在装配过程中发生断裂的问题,分别采用电感耦合等离子体发射光谱法、扫描电镜与金相检验的方法,进行了化学成分分析、断口分析、表面形貌观察与显微组织分析。结果表明:螺钉的化学成分符合要求;螺钉先发生脆性开裂,后发生韧性断裂;螺钉的螺纹表面存在麻点、缺口与伤痕等缺陷。螺纹表面的麻点、缺口与伤痕等缺陷是因为螺纹在滚压成形的过程中由于磨具和材料润滑不好,发生了粘连和嵌入而形成的。其中根部表面形成的一处严重伤痕在螺纹受力过程中产生应力集中,形成裂纹源并断裂。

Analysis on Fracture Cause for Titanium Alloy Ti6Al4V Screw

Aiming at the fracture of titanium alloy Ti6Al4V screw in the assembly process, chemical composition analysis, fracture analysis, surface morphology observation and microstructure analysis are carried out by inductively coupled plasma atomic emission spectrometry, scanning electron microscopy and metallographic examination. The results show that the chemical compositions of the screw meet the requirements, that the brittle crack comes first to the screw and then the ductile fracture, and that the screw thread surface has defects such as pitting, notch and scar. From the comprehensive analysis results, it can be seen that during the roll forming process, due to the poor lubrication of the abrasive and material, the screw and the mould adhere, so the pitting, notch and scar are formed on the thread. There is stress concentration appears in a serious scar formed on the surface of the root during the loading process, which becomes a crack source and then fractures.