Fracture toughness and strength of Al{sub}2O{sub}3-ZrO{sub}2 nanocomposites

摘要

Pure alumina, zirconia and nanocomposites Al{sub}2O{sub}3 -ZrO{sub}2 (20 - 80wt%) were studied in order to optimize some mechanical properties. ZrO{sub}2 was in tetragonal phase (stabilized with 3 mol% Y{sub}2O{sub}3). All the composites have the grain size D < 1μm. The following mechanical properties of the composites were studied: density d, Young's modulus E, Vickers hardness HV, flexural strength σ{sub}c, and fracture mechanics parameters as: toughness K{sub}(Ic), work of fracture WOF, threshold stress intensity factor K{sub}(Ii), parameters of subcritical crack growth n and log A. Some direct optical observations of crack growth from notch and Vickers indent were made too. In function of ZrO{sub}2 content d increased, E decreased, σ{sub}c, K{sub}(Ic), WOF and K{sub}(Ii) increased, HV decreased (above 40% ZrO{sub}2). It was claimed on the base of own studies and literature data that the best composites for structural material should contain 60-80 wt% ZrO{sub}2. In that range of ZrO{sub}2 content an additional strengthening effect arising from shielding (closure) of microcracks by local compressive residual stresses for Al{sub}2O{sub}3 particles could appear. It added to phase transformation contribution to strength and toughness.