Development of the next generation high strength Mg alloys for the automotive industry

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For decades, technological advancements have been driven by the progress in materials science. For example, the substitution of iron components in automobiles with lighter aluminum components during the 1970's and 80's resulted in an immediate performance and fuel economy enhancement. Recently, the Environmental Protection Agency and the Dept. of Transportation in USA mandated automakers to decrease greenhouse gas emissions and improve fuel economy by over 50% by 2025, otherwise face economic penalties. It is generally accepted that such a drastic improvement is achievable either by vehicle hybridization, or by vehicle weight reduction. Both approaches face challenges: 1) Hybridization is costly and adds weight to vehicles, and 2) Existing manufacturing processes for lightweight alloys are approaching technological limits and further advancements are costly. In this Discovery program, we will explore an innovative multi-process approach to overcome the limits associated with existing manufacturing methods for ultralight high-strength magnesium (Mg) alloys. Specifically, an advanced powder metallurgy process (Spark Plasma Sintering, SPS) will be combined with a traditional metalcasting process to develop castable Mg alloys with tensile properties and ductility comparable to wrought Mg alloys. Using SPS, nano- and micro-scale ceramic reinforcements will be blended and sintered into a Mg powder matrix to form “Dual-Phase Advanced Ceramic Modifier” (DP-ACM) discs. The sintered DP-ACM discs will be subsequently added to liquid Mg alloys during casting, resulting in dissolution of the Mg matrix of the DP-ACM within the melt, followed by a homogeneous release of the ceramic reinforcements in the melt. The reinforcements will serve to simultaneously enhance the room temperature strength and ductility (via grain refinement and the modification of eutectics) and creep resistance (via grain boundary pinning). This novel approach is anticipated to overcome several critical challenges (e.g., particle settling, flotation or oxidation) associated with current treatment methods for liquid Mg alloys. In addition to fabricating the DP-ACMs for the treatment of liquid Mg alloys, our group will also investigate the effect of SPS process parameters on the sinterability of metallic and ceramic materials. Specifically, our work will focus on the presently unknown effect of the electric current and powder morphology on the fusion of powder particles during SPS processing. The generated knowledge will enable sintering of materials with precisely controlled microstructure and properties. Experimental work in both areas will be carried out at my UBC laboratories and will provide HQPs hands-on and fundamental knowledge in the fields of manufacturing and materials science. This program will provide a foundation for a novel approach to develop castable high-strength Mg alloys.