On the unexpected formation of rare earth hydrides in magnesium–rare earth casting alloys

Abstract

There have been reports on the presence of rare earth (RE) hydrides in Mg–RE-based alloys either in the as-cast condition or after high-temperature heat treatment. However, the origin of the RE hydrides remains unclear. In this work, the formation of RE hydrides was investigated using binary Mg–La, Mg–Ce and Mg–Nd alloys. It is proposed that the RE hydrides are probably formed as a result of the decomposition of Mg–RE intermetallic phases by hydrogen.