Plastic Softening of Magnesium Oxide at High Temperatures by Nickel Oxide Addition

Magnesium oxide single crystals containing 0.3% nickel oxide were tested in tension at high temperatures. The stress‐strain relationship and deformation modes were similar to those identified for pure magnesium oxide. Alloy specimens had lower yield and ultimate strengths than pure magnesia at all temperatures above 1200° C and showed a greater tendency for kinking, polygonization, and recrystallization. It is proposed that the reducing atmosphere in the furnace causes the alloy crystals to decompose by the removal of oxygen and internal precipitation of nickel. The excess vacancies so produced enhance the nonconservative mobility of dislocations.