Ion implanted precipitate microstructure and mechanical properties of ceramic surfaces

Abstract

Microstructure of precipitates produced by annealing ion implanted surfaces have been investigated in the Al₂O₃-ZrO₂ system and both microhardness and indentation fracture toughness have been measured for correlation with microstructure. Air annealing of 190 keV high dose implants of Al⁺ in yttriastabilized zirconia and Zr⁺ in AI₂O₃ have resulted in A1₂O₃ and ZrO₂ precipitates, respectively, as would be expected from phase equilibria. However, annealing schedules drastically alter precipitate microstructure (i.e., crystallite size, morphology, orientation), and changes in microstructure have produced significant variation of surface mechanical properties. Crystallization of the ZrO₂ films on AI₂O₃ was observable by conventional XRD. The precipitated ZrO₂ was in the monoclinic structure if the grain size was large or in the tetragonal state if grain size was small. Being able to produce tetragonal ZrO₂ particles in A1₂O₃ surfaces suggests the possibility of transformation toughening and strengthening.