Effect of Filler Material on Fatigue Strength in Mg-4%Al-1%Ca-0.2%Mn Alloys and its MIG and TIG Weld Joints

The effect of filler material on Mg-4%Al-1%Ca (hereinafter referred to as AX41) non-combustible magnesium alloy TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas) weld joint was investigated through plane bending fatigue test and crack propagation test. Two types of filler materials were used in the welding process: one was the same as the base material, AX41, and the other was Mg-6%Al-1%Zn-1%Ca (hereinafter referred to as AZX611), which had a higher Al content compared to AX41. According to the results of plane bending fatigue test, the weld joint that used AZX611 as filler material showed higher fatigue strength properties compare to the joints that used AX41 as filler material. Fatigue crack initiated from welding defects in MIG weld joints, and it initiated from both defect and grain interior in TIG weld joints. In the MIG weld joints, the crack propagation resistance was improved with increase in Al content, which resulted the high fatigue strength properties in MIG weld joint which used AZX611 as filler material. In the TIG weld joints, the joint that used AX41 as filler material showed the similar crack propagation resistance with joint that used AZX611 as filler material. However, the enhanced mechanical properties and decreasing in grain size might increased the crack initiation life, which resulted the longer fatigue life in TIG weld joint that used AZX611 as filler material.