Effects of Butt Design and Gap Width on the Microstructure and Mechanical Properties of Magnesium Alloy Welds

The effects of parallel and angular butt designs with different gap widths on the microstructure and mechanical properties of the resultant magnesium joints in gas tungsten arc welding were investigated. The experimental results displayed that the tensile strength of the joint made with angular butt joint and 0.3 mm-wide gap reached 266 MPa, the joint fractured through the heat-affected zone or base metal during tensile testing, and the microstructure examination showed that no macropore appeared in the fusion zone. However, macropores in diameter of larger than 200 micron occurred for other joint designs, the tensile strength of the resultant joints decreased, and the joints fractured through the fusion zone during tensile testing. The fracture surfaces were examined by scanning electron microscopy and the microhardness distribution in the joints was measured by using a Vickers microhardness tester.