UC Riverside

The transportation industry is constantly seeking methods to save weight in their products and thereby improve fuel efficiency. The high specific strength and stiffness of magnesium alloys make them an attractive option; however, their poor overall strength and formability hinder the adoption of magnesium on a larger scale. One solution to improving strength is grain refinement, which has allowed magnesium strengths to reach levels not previously seen, however, maintaining the fine grain sizes and resulting strength is difficult as magnesium exhibits poor thermal stability against grain growth at low homologous temperatures. Other mechanisms of strengthening include inclusion of nano-spaced planar defects, the introduction of fine precipitates or particulates, and texture control among others. All of these efforts to strengthen magnesium are typically accompanied by a drop in low-temperature uniform plasticity, which in most magnesium alloys is limited to begin with. This dissertation examines three different Mg alloy systems whose processing-structure-property combinations seek to minimize the aforementioned trade-offs. vi

Some remaining knowledge on the ability to strengthen Mg alloys via nano-spaced planar defects was unraveled, and the contribution of texturing was ruled out. This research has also successfully strengthened Mg alloys via various processing approaches and resulting strengthening mechanisms while considering emerging understandings on the role of grain size in the micrometer and sub-micrometer regimes, and contributions of particulates to enhanced stability against grain grow and elevated temperature conditions. These finding may contribute to the design of high-strength Mg alloys and processing methods that increase the design space for their use in transportation and other applications.