Structure-environmental performance relationship studies of wrought mg alloys with an aim towards increasing their utilization in the transportation industries

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Reducing the overall mass of automobiles by the use of lightweight alloys is one of the means by which improved fuel efficiency and reduced harmful emissions can be attained. Mg alloy components, with their high specific strength and stiffness, provide significant opportunities to achieve these goals. However, there are two major technological issues preventing widespread application of wrought Mg alloy products, namely the relatively low production rate and the development of new alloys with a combination of high strength, high ductility and high corrosion resistance. The proposed research program will develop strategies to improve the corrosion resistance by achieving an improved understanding and prediction of the environmental degradation associated with wrought Mg-Al-Zn alloys. To this end, the research will characterize and elucidate the influence of (1) crystallographic orientation on the structure, composition and stability of the quasi-passive film formed on unalloyed single crystal and polycrystalline Mg, and (2) composition, size & distribution of intermetallic phases on the micro-galvanic activity in polycrystalline Mg-Al-Zn alloys, as a function of the alloy content, and the thermomechanical processing route (sheet, extrusions and forgings). An encompassing combination of micro- and nano-scale resolution probe techniques will be utilized to achieve these goals. Structural and compositional information on the matrix, intermetallic phases and passive film will be obtained using high resolution electron microscopy, whereas the localized electrochemical activity of the matrix and intermetallic phases will be obtained using high resolution scanning electrochemical probe techniques (SKP and SVP). A minimum of three HQP will be trained in this proposal. In addition to helping the industry attain their weight reduction targets for fuel economy, emissions and performance, the technology developed with the HQP will create a Canadian "know-how" that will effectively support innovation efforts of domestic suppliers.