Effect of bonding temperature on interface properties of AZ31 magnesium alloys joined by transient liquid phase using silver interlayer

In this study, AZ31 magnesium alloy was self-joined by employing the transient liquid phase (TLP) technique and using a silver interlayer. Effect of bonding temperature, which ranged from 480 °C to 500 °C temperature, on the joint microstructure and mechanical properties was investigated at a constant 1 h holding time. Microstructural studies showed that at the joining temperature of 480 °C, a large amount of un-diffused silver in the form of intermetallic compounds and a eutectic phase were identified in the joint interface. However, increasing the temperature to 500 °C resulted in an increased diffusion rate of silver atoms into the metallic substrate. Finally, the isothermal solidification phenomenon was evidenced, due to the complete disappearance of the eutectic phase and intermetallic compounds. The uniform chemical composition at the joint interface, was achieved at the 500 °C temperature. Continuous increase in the shear strength of the joints was evidenced in the samples joined, that at higher temperatures reached to a value of 39 MPa for the sample joined at 500 °C temperature. Microstructural analysis of the joint surfaces showed that the samples with the lowest joint strength had the characteristics of a cleavage fracture.