超声功率对7075铝合金CMT焊接接头的组织与性能的影响

Effect of Ultrasonic Power on the Microstructure and Properties of 7075 Aluminum Alloy CMT Welding Joint

为了解决铝合金接头的气孔多、晶粒粗大、力学性能差等问题,使用冷金属熔滴过渡(CMT)焊接方法完成对7075铝合金薄板的焊接,在焊接过程中引入超声波。通过金相、EBSD、力学性能等测试考察了不同超声功率对焊接接头气孔、微观结构和力学性能的影响。结果表明,超声振动可以显著地减小气孔数量、增加熔宽,并且其焊接热影响区(HAZ)的宽度随超声功率的增加而减小;超声功率为1200 W时焊接接头显微硬度较无超声提高87.514 MPa,抗拉强度提高85 MPa,断后伸长率提高1.4%。由EBSD结果分析可知,当超声功率为1200 W时焊缝平均晶粒尺寸36.89μm,比未施加超声时减小了9.99μm,焊缝晶粒得到了明显细化;随着超声功率的增加提高了晶粒的大角度晶界的比例,焊接接头的塑性有所增加。

In order to solve the problems of many pores,coarse grain and poor mechanical properties of the aluminum alloy joints,the welding of the 7075 aluminum alloy thin sheet was completed using the CMT welding method,and the ultrasonic wave was introduced in the welding process.The influence of different ultrasonic power on welded joint stomata,microstructure and mechanical properties were investigated by metallography,EBSD,and mechanical properties test.The results show that ultrasonic vibration can significantly reduce the number of pores and increase the melting width,and the width of heat affect zone(HAZ)decreases with the increase of ultrasonic power.When the ultrasonic power is 1200 W,the microhardness of the welding joint is higher than that without ultrasound,the tensile strength is 85 MPa higher,and elongation after fracture is 1.4%higher.According to EBSD results,the average grain size of the weld is 36.89μm when the ultrasonic power is 1200 W,9.99μm less than that without ultrasound.The weld grain is refined obviously.With the increase of ultrasonic power,the proportion of large angle grain boundaries increases,and the plasticity of welding joints increases.