Study on Microstructure and Properties of AZ31/6061 GTAW Butt Joints According to Mg-Cd-Al Ternary System

AZ31 Mg and 6061 Al were successfully joined by GTAW method with Cd as filler metal. The tensile strength of the joints reached 170 MPa through this alloying method according to Mg-Cd-Al ternary system. The microstructure, phases, element distribution and fracture mechanism of alloyed joints were studied. The results suggest that the fusion zone is mainly composed of CdMg compounds and Al-based solid solution. A transitional zone thickness of 40-80 μm with few primary Al₁₂Mg₁₇ and fine Al₁₂Mg₁₇-MCMS (MCMS represents a mixture of CdMg and CdMg₃ compounds) eutectic is formed between the AZ31 base metal and fusion zone. The fracture surface presents three distinct regions because of the different distribution of Al₁₂Mg₁₇ compounds in the transitional zone. The alloying with Cd filler metal can disperse Al₁₂Mg₁₇ intermetallic compounds and form CdMg ordered compounds with excellent plasticity. Thus, the mechanical properties of alloyed joints have been significantly enhanced.