HCP Mg Alloys Formable at Room Temperature
Technical Report,10 May 2016,09 Feb 2017
Northwestern University Evanston Campus Evanston United States
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Magnesium Mg is an attractive material for many lightweight applications because of its low density. Mg has a hexagonal close-packed HCP crystal structure with only 2 active slip systems available at room temperature for plastic deformation therefore, it has poor room-temperature ductility and formability. As a result, Mg alloy components are manufactured via casting or elevated-temperature forming, processes that are time- and energy consuming. Several approaches to improve the ductility of Mg alloys involve the use of rare-earth elements that are costly and may not be strategically available. It was demonstrated in this project that addition of lithium to Mg or formation of nano-sized precipitates improves the ductility of the alloys at room temperature after specific heat-treatment, these Mg alloy plates did not form cracks when bent on themselves 180 around a mandrel at room temperature. The ductilization model for Mg alloys was developed. The improvement in ductility at room temperature is related to the interaction between solute atomsclustersnano-precipitates with screw dislocations that reduces the Pieirls stress and activates additional slip systems for plastic deformation. This model could be applicable to other metals with limited number of slip systems for plastic deformation.
- Metallurgy and Metallography