The pulsed power ultrasonic-assisted gas metal arc welding (PU-GMAW) is a new development hybrid welding method. The influences of the pulsed power ultrasonic on the microstructure evolution of the welded joint of Al–Cu alloy were investigated by using scanning electron microscopy, transmission electron microscope and electron back scattering diffraction. The results showed that the efficient heat input in the PU-GMAW was increased by above 100% compared with the traditional GMAW. The grain and eutectic of the PU-GMAW weld seam were refined compared with that of the GMAW. Cavitation and acoustic streaming induced the dendrite fragmentation (α-Al) and heterogeneous nucleation, which were the main reasons for the grain refinement. The microhardness of the PU-GMAW welded joint was improved compared with that of the GMAW owing to the change of the eutectic and grain.

中文翻译：

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脉冲功率超声辅助气体保护焊中铝铜合金接头的组织演变和性能

脉冲功率超声辅助气体保护金属电弧焊（PU-GMAW）是一种新型的混合焊接方法。利用扫描电子显微镜，透射电子显微镜和电子背散射衍射技术研究了脉冲功率超声对铝铜合金焊接接头组织演变的影响。结果表明，与传统的GMAW相比，PU-GMAW的有效热量输入增加了100％以上。与GMAW相比，PU-GMAW焊缝的晶粒和共晶更加细化。空化和声流引起枝晶破碎（α-Al）和异质形核，这是晶粒细化的主要原因。由于共晶和晶粒的变化，与GMAW相比，PU-GMAW焊接接头的显微硬度有所提高。