Delta to alpha prime transformation of plutonium during microhardness testing

Metallic plutonium is a complex material that can exist in six allotropic phases at ambient pressures; and under stress, it can transform martensitically from the ductile face centered cubic delta phase to the brittle monoclinic alpha prime phase. This investigation found that the pressures generated during microhardness indentation are sufficient for the transformation to occur. Micrographs showing the transformation as well as pressure calculations are presented in support for this finding. Also, based upon the amount of material displaced by the indenter, it was determined that there is at least a 16% error in published hardness values of the delta phase that can be attributed to the delta to alpha prime transformation.