Examination of Gas Metal Arc Welding as a potential method for additively manufacturing parts out of magnesium alloys

The potential use of Gas Metal Arc Welding as a rapid material deposition method in additively manufacturing parts out of magnesium alloys was investigated. A 3-axis CNC with an integrated welding torch was designed and built to print multi-row and multi-layer blocks of AZ92a magnesium on AZ31b substrates. Multiple welding parameters were studied to determine the behavior of the material during the deposition process to obtain the most suitable heat input settings for this method. Different print orientations, overlap percentages, and block geometries were examined to reduce both the size and frequency of occurrence of internal voids in the magnesium parts. Wire EDM was used to cut tensile test specimens out of the finished blocks, which were subsequently tested in an Instron 5582 to determine the stress-strain relationship, yield strength, and tensile strength. Samples were printed in two different orientations: i.) with short beads deposited in the direction normal to the direction of the applied tensile test force and ii.) with long beads deposited in-line with the direction of the applied tensile test force. Regardless of orientation, the range for determined yield strength of the samples was between 90 and 120 MPa. Determining the tensile strength proved more challenging due to the presence of internal voids causing material fracture at different stress levels. Most samples showed a tensile strength of 145 to 155 MPa, with some samples printed in-line with the applied pull direction showing a tensile strength of up to 216 MPa. SEM analysis was performed to analyze the fracture surfaces of the tested specimens and was used to analyze the imperfections in the deposited material in the forms of cracks, trapped spatter, and impurities. Optical microscope analysis was performed as well to examine the resulting final grain structure of the material.