Friction Stir Welding and Processing of Magnesium Alloy AZ31B

Abstract

The implementation of magnesium for use in the automotive and aerospace industries is proving to be a cost-effective way to increase fuel efficiency by decreasing structural weight. Several challenges arise, however, in the joining of magnesium alloys, especially with dissimilar materials. Joints such as these can be achieved through friction stir welding (FSW), as the solid-state process facilitates the joining of low-density materials. This thesis furthers existing research on implementation of magnesium alloys: first by analyzing a novel dissimilar lap weld between magnesium alloy AZ31B and aluminum 5052; second by introducing preliminary results of friction-stir processing (FSP) with additive boron nitride particles for increased galvanic corrosion resistance in AZ31B. The most successful Al-Mg lap joints were produced at a tool rotation of 1000 rpm and traverse speed of 101.6 mm min-1: these welds demonstrated lap shear strength up to 60.8% that of base material. The increased shear strength of these specimens is supported by evidence of strong material mixing and dispersed intermetallic compound formation. Results show that Al-Mg lap welds are possible through FSW, but point to a need for parameter and tool optimization to promote increased stirring activity. Preliminary corrosion testing of AZ31B subjected to additive FSP is evaluated as a potential future study.