Experimental Characterization of Deformation Mechanisms in Magnesium Rare Earth Alloys

Johns Hopkins University, Baltimore MD

Investigators

Abstract

Nontechnical abstract: The overall versatility, deployability and energy efficiency of modern manned and autonomous vehicles are inversely related to their weight. Magnesium (Mg) is nearly four times lighter than steel and its ultra-low density and high specific strength make Mg alloys attractive lightweighting materials for commercial and defense platforms. However, the use of Mg has been inhibited by its limited ductility and formability, which is attributed to strong plastic anisotropy that results from its hexagonal crystal structure. Recent gains in formability have been achieved through rare earth alloying, and this project will provide a detailed understanding of the influence that these rare earth elements have on the atomic-scale mechanisms that govern ductility and formability. The insights obtained from this experimental study will accelerate alloy development and help promote cost-effective lightweighting in a wide variety of automotive, military and aerospace applications. Collaborations will provide meaningful STEM educational and career advancement opportunities, and participation in SABES will offer JHU researchers a chance to personally interact with and give Baltimore elementary school students a unique perspective on STEM activities. Technical Abstract: The scientific merit of this study is predicated in our desire to see and understand the deformation mechanisms that underpin the mechanical response of Mg alloys and to elucidate the fundamental role that rare earth elements have in increasing ductility and improving formability. The experimental tasks to be undertaken include: (i) identification of active slip systems in Mg-RE alloys, (ii) meso-scale characterization of dislocation morphologies and microstructures, (iii) atomic-scale characterization of dislocation cores, and (iv) identification of the factors influencing twin nucleation and growth. SEM-based EBSD mapping and STEM observations and TEM-based bright field, weak-beam dark field, HREM, and STEM imaging and nanoscale orientation and elastic strain mapping will be employed. The experimental data collected will be digitally archived and used to promote Integrated Computational Materials Science and Engineering (ICMSE) as envisaged by the Materials Genome Initiative (MGI).