超声辅助镁合金搅拌摩擦焊接头厚度方向组织与性能研究

Study on the microstructure and performance in thickness direction of friction stir welding assisted by ultrasonic vibration

针对镁合金搅拌摩擦焊接头组织性能不均匀问题,对4 mm厚AZ31镁合金进行超声辅助搅拌摩擦(ultrasonic vibration friction stir welding,UFSW)对焊,研究了超声振动对镁合金FSW接头厚度方向组织性能的影响.结果表明:施加超声辅助后,焊缝上中部晶粒明显细化,硬度值提升.同时,超声波的体积效应可以降低金属的流变应力,改善材料流动性,焊缝底部的未焊合缺陷得到明显改善,接头整体及各分层的抗拉强度和断后伸长率均得到提升.

In order to solve the problem of uneven microstructural and performance in magnesium alloy friction stir welding joints,the ultrasonic vibration was used to assist the 4 mm AZ31 magnesium alloy friction stir welding process.The microstructure and mechanical properties in thickness direction were analyzed to reveal the influence of ultrasonic vibration on FSW.The results show that with the assistance of ultrasonic vibration,the microstructure in the upper part of the weld is significantly refined and the hardness value is improved.At the same time,the volumetric effect of ultrasonic vibration can reduce the rheological stress of metal and improve the fluidity of materials.The unwelded defects at the bottom of the weld are nearly eliminated.The tensile strength and elongation of each part of the weld are both improved by ultrasonic vibration.