Rare Earth Additions for Improving Mg Alloys in Automotive ApplicationsDonald S. Stone, University of Wisconsin-Madison, DMR 1005762Intellectual Merit • Rare earth (RE) elements like Nd, Sm and Ce are known to improve mechanical properties (strength, ductility, impact toughness) of Mg alloys, making them more viable for automotive applications. • To help with design and processing of new class of Mg-Zn-RE alloys, we survey phase equilibria, solidification, and age hardening in Mg-Zn-RE ternary systems. • Collaborative research with Alan Luo at General Motors employs a new, thermodynamics-based approach to computational materials design. This approach allows us to target a few, carefully chosen compositions for experi-ments that generate the phase diagram. • A new experimental method called broadband nanoindentation creep generates hardness (yield stress) across 4-6 decades of strain rate to probe hardening mechanisms at microscopic length scales. Array of nanoindents for probing mechanical proper-ties in NZ30K; Each indent is about 5 m across, or 1/20th diameter of human hair Scanning electron micrograph, and X-ray maps of elements in as-cast NZ30K (Mg-3.0% Nd-0.2% Zn- 0.5% Zr) Broadband nanoindentation creep (BNC) spectra from heat treated NZ30K. From the shapes of these curves we can identify hardening mechanisms
Rare Earth Additions for Improving Mg Alloys in Automotive ApplicationsDonald S. Stone, University of Wisconsin-Madison, DMR 1005762Broader Impact • The results of this basic study will enable materials engineers to develop efficient processes for fabricating low-density Mg alloys with superior performance. • We have invited Dr. Alan Luo of General Motors to join Materials Science and Engineering at UW Madison as an adjunct professor. He meets with undergraduates, presents guest lectures in classes, supervises graduate students, and serves on thesis committees. • Graduate student Shawn Xia has spent the summer of 2012 at GM Research and Development Center studying phase equilibria in the Mg-Zn-Sm system. Graduate student Amirreza Sanaty-Zadeh’s poster won a Best Poster Award at the 9th International Conference on Magnesium and its Alloys held in Vancouver, BC.