Achieving equiaxed microstructure and isotropic mechanical properties of additively manufactured AZ31 magnesium alloy via ultrasonic frequency pulsed arc

The high cooling rate and thermal gradient in the wire arc additive manufacturing (WAAM) process often leads to a tendency towards columnar grains or columnar dendrites in magnesium alloys, which can result in anisotropic mechanical properties and are therefore undesirable. To address this challenge, a novel ultrasonic frequency pulsed (UFP) arc used as heat source is applied to alter the conditions in the WAAM process and promote equiaxed growth of magnesium grains. Experimental results indicate that the AZ31 magnesium alloy deposit produced by the UFP-WAAM exhibits full equiaxed-grain microstructure along the building direction. Without any additional treatments, the AZ31 magnesium alloy deposit displays promising mechanical properties, such as isotropic tensile strength and excellent ductility.