Microstructure evolution and mechanical properties of ultrasonically TLP bonded Mg joint

AZ31B Mg alloys were joined with a pure Zn interlayer via ultrasonic-assisted transient liquid phase bonding. The formation and evolution of intermetallic compounds (IMCs) and the mechanical properties of the bonded joints were investigated. Results showed that joints could form within an extra short time of 0.1 s via eutectic reaction, eutectoid reaction and diffusion bonding. Mg-Zn eutectoid structures, IMCs of MgZn and MgZn2 formed inside the bonded joint. The width of the MgZn2 phase decreased with prolonged ultrasonication time, high ultrasonication power, and sonotrode pressure. The entire joint was characterized by eutectoid structures without MgZn2 at a high sonotrode pressure of 0.4 MPa. MgZn2 had a higher hardness and modulus than MgZn, Mg-Zn eutectoid structure, and Mg substrate. Joints fractured through the MgZn2 phase and eutectoid structure had shear strength values of 30 and 40 MPa, respectively.