FRG: Fundamental Approaches to Design of New Magnesium Structural Alloys

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TECHNICAL: Magnesium alloys have the lowest density among all structural alloys and possess high specific strength, but new alloys must be developed for use in the service temperature range of 150-250 C. The identification of new alloying approaches that provide strengthening and stability at these temperatures, within the constraints of casting processes that are viable for automotive-scale production, remains a critical materials challenge. The relative lack of fundamental understanding of the behavior of potential high temperature magnesium alloys systems, compared to that for other structural alloy systems, has been identified as a critical obstacle to significant progress in the search for new lightweight, high temperature magnesium systems. To address this a collaborative research program (FRG) between the University of Michigan and the University of Wisconsin, with strong collaboration from Ford Motor Company and General Motors is initiated. Key gaps in the fundamental understanding of solidification, phase equilibria and deformation mechanisms in selected magnesium alloy systems will be investigated in order to establish a strong foundation for the design of alloys that meet the multiple demands required for potential use at high temperature. This will be accomplished by: (1) selection of promising systems on which future alloy development programs are likely to be conducted, (2) establishment of full thermodynamic descriptions of these systems through a combined modeling and experimental effort, (3) evaluation of key aspects of the solidification behavior of these systems under realistic casting conditions and (4) investigation of mechanisms of high temperature deformation creep. Two quaternary systems, Mg-Al-Ca-Sr and Mg-Al-Ca-Nd, will initially motivate the research and will permit us to build on existing academic and industrial collaborations. Anticipated outcomes include (1) definition of microstructural modification strategies for improvement of creep properties, (2) identification of higher order elemental additions that can be used to alter solidification paths for critical microstructural control, (3) realistic approaches for improving the stability of intermetallic phases near the grain boundaries, (4) refined thermodynamic descriptions and alloy design tools and (5) new quantitative approaches for evaluation of solidification and casting behavior of Mg-based systems. NON-TECHNICAL: The research program is designed to stimulate a more concentrated national research effort on high temperature cast magnesium alloys, by serving as a nucleus of research activity and university/industry collaboration. The educational experience of the undergraduate and graduate students in the program will be greatly enhanced by interactions with industrial personnel as well as by direct access to their unique research facilities, particularly those of the Ford Motor Company and General Motors. A particular strength of the core collaborative group is the physical proximity of the University of Michigan and the University of Wisconsin to each other and to the U.S. automotive manufacturers (and suppliers). The program would bring the U.S. academic activity on lightweight Mg alloys closer (but certainly not equivalent) to observed levels of research effort in Asia and Europe. The program will also enhance academic courses within the core MSE curricula at both Michigan and Wisconsin. Finally, resources from this program relating to energy efficiency and lightweight materials will be made available to the ASM International High School Teachers Camp, which is hosted annually at the University of Michigan.