TC4钛合金高锁螺栓发生异常双剪断裂原因

Causes of abnormal double shear fracture of TC4 titanium alloy high-lock bolt

某TC4钛合金高锁螺栓在双剪试验过程中发生异常断裂。采用宏观观察、显微组织观察、断口分析和双剪试验,分析了该高锁螺栓发生异常双剪断裂的原因。结果表明:在该高锁螺栓的热处理过程中,其在真空炉中未被及时取出,使螺栓在炉中长时间保温,形成较厚的表面污染层和显微裂纹;通过分析高锁螺栓的加工工艺可知,在热处理后的精车工序中,加工余量较小,导致螺栓表面污染层未被完全去除,在双剪试验过程中受弯矩作用,显微裂纹沿着脆而硬的表面污染层快速扩展,直至螺栓断裂。

A TC4 titanium alloy high-lock bolt was abnormally fractured during the double shear test.Through macroscopic observation,microstructure observation,fracture analysis and double shear test,the reasons for the abnormal double shear fracture of high-lock bolt were analyzed.The results showed that during the heat treatment process of high-lock bolt,they were not taken out in time in the vacuum furnace,so that the bolt were kept warm in the furnace for a long time,resulting in a thicker surface contamination layer and micro cracks.It could be seen from the processing technology of high-lock bolt that in the finishing process after heat treatment,the small machining allowance led to incomplete removal of the bolt surface contamination layer.During double shear test,the micro cracks spreaded rapidly along the brittle and hard,surface contamination layer under the action of bending moment until the bolt fractured.