Formability, microstructure evolution and mechanical properties of wire arc additively manufactured AZ80M magnesium alloy using gas tungsten arc welding

Wire arc additive manufacturing (WAAM) technology has been used to fabricate the multi-layer single-pass deposited wall of AZ80M magnesium (Mg) alloy by gas tungsten arc welding. The formability, thermal cycles, microstructural evolution and mechanical properties of the WAAM AZ80M Mg alloy were investigated. The results show that there was significant difference in the temperature variation and the geometries between the original several layers and the subsequent deposited layers. Owing to the arc energy input, the interpass temperature rised rapidly and then stabilized at 150 degrees C. As a result, the width of the deposited wall increased and then kept stable. There were obvious differences in the microstructure of the WAAM AZ80M Mg alloy among the top zone, intermediate zone and bottom zone of deposited wall. During the arc deposition process, the beta phase of the WAAM AZ80M Mg alloy redissolved due to the cyclic heat accumulation, and then precipitated in the grain boundary. The cyclic heat accumulation also led to weakening of dendrite segregation. From the substrate to the top zone, the hardness of the deposited wall decreased gradually, and the intermediate zone which was the main body of deposited wall had relatively uniform hardness. The tensile properties of the WAAM AZ80M Mg alloy were different between the vertical direction and the horizontal direction. And the maximum ultimate tensile strength of the WAAM AZ80M Mg alloy was 308MPa which was close to that of the as-extruded AZ80M Mg alloy. (C) 2020 Published by Elsevier B.V. on behalf of Chongqing University.