Anisotropy of mechanical properties and hardening mechanism in ZrO2-Y2O3 solid solution crystals

The phase composition inside and outside the indents on the {100}, {110} and {111} surfaces for 20, 3 and 1 N loads has been studied using local Raman spectroscopy. The degree of the tetragonal-monoclinic transition has been assessed for different crystallographic planes and different indenter diagonal orientations. We show that the tetragonal-monoclinic transition is anisotropic, this affecting the transformation hardening mechanism. The maximum amount of the monoclinic phase has been detected in the vicinity of the indent in the {100} plane for the <100> indenter diagonal orientation. The highest fraction toughness has also been observed in {100} plane for the <100> indenter diagonal orientation. Probably, this indenter diagonal orientation provides for the maximum stress orientation along the coherent conjugation planes between the tetragonal and the monoclinic phases during the tetragonal-monoclinic transition, i.e. (100)t || (100)m and [001]t || [010]m.