MICROSTRUCTURE, MECHANICAL-PROPERTIES AND THERMAL-SHOCK BEHAVIOR OF AL2O3+ZRO2+SICW COMPOSITES

The strengthening and toughening effects and mechanisms of combining b oth whisker reinforcing and zirconia phase transformation toughening i n the Al2O3 matrix were systematically investigated in this paper. TEM observations showed that most of the SiCw/Al2O3 and SiCw/ZrO2(2Y) int erfaces are bonded tightly and there are no distinct second phases or intermediate layers formed at the interfaces. The addition of SiCw or ZrO2(2Y) particles evidently improve the mechanical properties of Al2O 3 ceramics and the more obvious strengthening and toughening effects c an be obtained by adding both SiCw and ZrO2(2Y) particles simultaneous ly to the Al2O3 matrix. The main toughening mechanisms in the Al2O3 ZrO2 + SiCw composites are whisker bridging and pull-out, crack deflec tion as well as dynamic t-m phase transformation toughening and microc rack toughening. The toughening effects of both SiCw and ZrO2(2Y) part icles are shown to be additive, but the addition of ZrO2(2Y) particles decreases the strengthening effect of SiCw. The addition of SiCw can obviously improve the thermal shock resistance of Al2O3 and Al2O3 + Zr O2(2Y) ceramics and the thermal shock resistance of Al2O3 + SiCW compo sites can be further improved by adding a few of ZrO2(2Y) particles (1 0 vol%). (C) 1998 Elsevier Science Limited and Techna S.r.l. All right s reserved.