Ion implanted precipitate microstructure and mechanical properties of ceramic surfaces

Microstructure of precipitates produced by annealing ion implanted surfaces have been investigated in the Al sub 2 O sub 3 --ZrO sub 2 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 exp + in yttria-stabilized zirconia and Zr exp + in Al sub 2 O sub 3 have resulted in Al sub 2 O sub 3 and ZrO sub 2 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 ZrO sub 2 films on Al sub 2 O sub 3 was observable by conventional XRD. The precipitated ZrO sub 2 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 ZrO sub 2 particles in Al sub 2 O sub 3 surfaces suggests the possibility of transformation toughening and strengthening. 10 ref.--AA