The microstructure in the bonding interface region of an ultrasonic spot welded Cu/Ni joint was investigated. At the copper side near the bonding interface, all the refined grains with random orientations and high-angle grain boundaries are < 5 nm in size. Nano-sized undulations occur at the Cu/Ni interface. The formation of nano-sized grains and undulation characteristics is ascribed to the dynamic recrystallization as well as shear instability in ultrasonic spot welding.

中文翻译：

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超声点焊Cu / Ni接头的键合界面区域内小于5 nm的细化晶粒和纳米级波动的形成

研究了超声点焊Cu / Ni接头的结合界面区域的显微组织。在键合界面附近的铜侧，所有具有随机方向和高角度晶界的精炼晶粒尺寸均小于5 nm。纳米尺寸的起伏发生在Cu / Ni界面。纳米晶粒的形成和起伏特性归因于超声点焊中的动态再结晶以及剪切不稳定性。