10 µm

1. Improved Magnesium Alloys for Automotive ApplicationsSurya R. Kalidindi, Drexel University, DMR 1006784 New Twin Orientations b) Magnesium (Mg) alloys possess the light weight and high specific strength sought after by automotive manufacturers to significantly reduce vehicle weight resulting in enhanced fuel efficiency and decreased CO2 emissions. Although these alloys have been used successfully in castings, their limited formability has hindered their potential use in automotive structural components. This research aims to understand the precise roles and extent of various deformation, recrystallization, and recovery mechanisms in controlling the microstructure evolution of Mg alloys subjected to thermo-mechanical processes of interest to the automotive industry. It was found that annealing previously cold worked Mg alloy AZ31 resulted in recrystallized nuclei preferentially forming within contraction twins distributed far from the starting orientation (i.e. beneficial for further sheet processing). However, the final recrystallized texture was not significantly changed due to two findings: (1) The rate of contraction twin nuclei growth significantly decreased after an initial quick growth; and (2) Many of the starting grains were incompletely recrystallized. These two findings are expected to be related to the extreme amount of recovery observed in this material that would account for slowed boundary mobility. c) a) 10 µm Lack of Twin Growth d) Model for Contraction Twin Contribution Contraction Twin Highly Deformed Area Twin nuclei competing with nuclei at grain boundaries RX Nuclei Form Preferentially within Twins Nuclei at Grain Boundaries

2. Improved Magnesium Alloys for Automotive ApplicationsSurya R. Kalidindi, Drexel University, DMR 1006784 Education– this grant supported two Ph.D. students, Amanda Levinson and Ali Khosravani, at Drexel University. Collaboration– Collaboration between industry (General Motors) and academic (Drexel University) partners on this grant is ongoing. One of the graduate students, Ali Khosravani, from the PI’s group is performing an internship at the R&D facility of General Motors in Warren, MI. Another collaboration, with the Dynamic Characterization Group at Drexel University was established to facilitate this research using transmission electron microscopy (TEM). Outreach– An undergraduate student, Mr. Sean Rodeheaver, participated in this work as a STAR (Students Tackling Advanced Research) scholar at Drexel University. A high school student, Mr. Parmpreet Mann, assisted on a sub-project and won 1st place for presenting his work at the Pennsylvania Junior Academy of Science. Dissemination of Knowledge – This work was presented as a seminar to the Army Research Laboratory in Aberdeen, MD and the Naval Research Laboratory in Washington, DC.