Solution and Precipitation Hardening in (Ca, Mn) Sulfides and Selenides

Abstract

The deformable sulfides and selenides of calcium and manganese develop extensive, but not complete, solid solubility. It was thus possible to use them to study both solution hardening and precipitation hardening in inorganic, nonmetallic compounds. Samples were first solution treated and quenched. Since phase separation was reasonably slow during cooling, it was possible to determine the amount of solution hardening over a wide temperature and composition range. It was also possible to precipitation harden and over-age these materials. Solution hardening and precipitation hardening are parallel to those found in metals. Cation substitution, as with anion substitution, leads to a harder compound when substituting species are more ionic,i.e., Ca²⁺-rich compounds are harder than Mn²⁺-rich compounds, and S^2--rich compunds are harder than Se^2--rich compounds. Precipitation hardening (and over-aging) occurs more rapidly with greater supercooling and with the lower-melting selenides.