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

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.