Improved Magnesium Alloys for Automotive ApplicationsSurya R. Kalidindi, Drexel University, DMR 1006784 ND 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. This work has provided strong evidence for the dramatically different roles of extension twins and contraction twins in the strain hardening and recrystallization processes1. Extension twins appear to be an important contributor to formability in these alloys, but are generally not effective in recrystallization. On the other hand, contraction twins appear to dramatically limit formability. In subsequent recrystallization, the contraction twins produce new grains that exhibit fairly slow growth kinetics. Further understanding of the precise roles of these deformation twins in microstructure evolution is essential to develop new processing routes for Mg alloys with superior performance characteristics suitable for automotive structural applications. Roller Hemming – processing step to produce closure between inner and outer automobile body panels. Final Hem Joint Four roller passes with a laser positioned ahead of the roller were required to hem Mg sheet. This image shows a microstructure map after the material was bent to an angle of 30o. Hemming without a laser resulted in early failure. a) b) c) d) e)
Improved Magnesium Alloys for Automotive Applications Surya R. Kalidindi, Drexel University, DMR 1006784 Education– This grant currently supports three Ph.D. students, two of whom are US citizens, at Drexel University. Collaboration– Collaboration between industry (General Motors) and academic (Drexel University) partners on this grant is ongoing. One of the graduate students, Shraddha Vachhani, from the PI’s group is performing an internship at the R&D facility of General Motors in Warren, MI. Outreach– An undergraduate student, Mr. Sean Rodeheaver, participated in this work as a STAR (Students Tackling Advanced Research) scholar at Drexel University. Dissemination of Knowledge –Work from this project was presented in the form of a poster for Drexel Research Day 2011 and the American Society of Materials (ASM) Philadelphia Chapter Poster Contest, and given as a talk at The Minerals, Metals and Materials Society (TMS) annual meeting and exhibition.