Xin Wang¹, Yang Hu¹, Kehang Yu¹, Subhash Mahajan², Irene J. Beyerlein³, Enrique J. Lavernia¹, Timothy J. Rupert¹, Julie M. Schoenung¹; ¹University of California Irvine, ²University of California, Davis, ³University of California, Santa Barbara

The deformation response of Mg and its alloys is critically influenced, not only by dislocation slip, but also by the nucleation and growth of deformation twins. An atomic scale characterization of the microstructure and chemical composition of twin boundaries (TBs) is therefore an appropriate approach to investigate the underlying mechanisms. In this work, we report on a somewhat unexpected solute segregation phenomenon: Y-rich columns and nanoscale Y-rich clusters segregated at the basal-prismatic (BP/PB) interfaces on {10-12} TBs after a small deformation of a Mg-3wt%Y binary alloy at room temperature. A similar Y-clustering was predicted by a hybrid Monte Carlo/molecular dynamics (MC/MD) method, with the driving force for Y segregation being provided by the misfit between Y atoms and Mg matrix and the tensile stress at the BP/PB interfaces. Segregation of Y to the BP/PB interfaces provides a pinning effect that affects the twinning dynamics and strengthening of Mg-Y alloys.