Microstructure evolution of Mg/Cu dissimilar metal jointed by ultrasonic-induced transient liquid phase bonding with Zn interlayer

Abstract

Abstract Ultrasonic-induced transient liquid phase bonding of Mg/Cu dissimilar alloys with Zn interlayer was carried out. The effects of pressure and temperature on the microstructure and mechanical properties of the weld seam were investigated. The formation of the Mg Zn solid-liquid interface, α-Mg solid solution spalling and merging growth behavior were analyzed. With the increase of pressure, the interface metallurgical reaction between the base metal and the interlayer was intensified, and the width of the weld seam decreased gradually. Solid solution, Mg Zn, Mg Cu, Cu Zn, and CuMgZn intermetallic compounds in the weld seam were detected. The fine granular eutectic structure has a tendency to transform into a layered eutectic structure gradually. A tendency to merge and grow for the adjacent α-Mg solid solution was observed. CuMgZn formed on the Cu side was embedded on the surface of Cu5Zn8, and remained in the weld seam. The thickness of CuMgZn increased with the increase of temperature. The fracture occurred between CuMgZn and Cu5Zn8, and the fracture manner was a brittle fracture. The highest average strength was 80.75\u202fMPa.