Deformation mechanisms of nil temperature ductile polycrystalline B2 intermetallic compound YAg

Abstract

The most ductile rare earth intermetallic compound, YAg, was subjected to an thermal activation analysis at low temperatures down to 4 K. Evaluation of the activation parameters and their dependence on stress and temperature yields strong indication for forest dislocation cutting as the rate-controlling deformation mechanism, similar to face-centered cubic metals. Surprisingly, nil temperature ductility was observed. Together with results of a detailed TEM analysis of the active slip systems it is concluded that, despite of violating the von Mises criterion for the plastic deformation of polycrystalline materials, a low elastic anisotropy and/or low Peierls stress is responsible for the appreciable ductility at low temperatures. This finding may help to search for other ductile systems in the broad class of intermetallic compounds.