Dissertation Presentation: Daniel Buey, Modeling non-basal deformation modes in Mg-Y and other Mg-RE alloys

Abstract

Magnesium’s high specific strength makes it an ideal candidate for automotive and aerospace applications, but its poor room temperature formability limits its practical application in industrial settings. The poor ductility is a result of the anisotropy of the plastic deformation response of the hexagonal close packed (HCP) crystal system, wherein non-basal slip systems are much harder to activate than basal slip modes. Alloying with yttrium and other rare-earth (RE) elements has been experimentally shown to drastically improve the ductility of Mg. An accurate representation of non-basal deformation is necessary to designing materials with the desired properties, but these deformation modes and their interaction with solutes are not well understood.

The behavior of several non-basal deformation modes is examined in an attempt to describe the behavior of these non-basal modes. Molecular dynamics (MD) simulations were used to examine the glide and cross-slip behavior of ác+añ screw dislocations between the first- and second-order pyramidal glide planes in pure Mg. Additionally, ab-initio DFT simulations were used to calculate the effect of solute atoms on the behavior of ác+añ edge dislocations and twinning dislocations.  The deformation behavior discussed provides insights into the complex deformation behavior seen experimentally in Mg-RE alloys.