Microstructure, mechanical properties and thermal shock behaviour of Al 2O 3+ZrO 3+SiCw composites

Abstract

The strengthening and toughening effects and mechanisms of combining both whisker reinforcing and zirconia phase transformation toughening in the Al 2O 3 matrix were systematically investigated in this paper. TEM observations showed that most of the SiCw Al 2 O 3 and SiCw ZrO 2(2 Y) interfaces are bonded tightly and there are no distinct second phases or intermediate layers formed at the interfaces. The addition of SiCw or ZrO 2(2Y) particles evidently improve the mechanical properties of Al 2O 3 ceramics and the more obvious strengthening and toughening effects can be obtained by adding both SiCw and ZrO 2(2Y) particles simultaneously to the Al 2O 3 matrix. The main toughening mechanisms in the Al 2O 3 + ZrO 2 + SiCw composites are whisker bridging and pull-out, crack deflection as well as dynamic t-m phase transformation toughening and microcrack toughening. The toughening effects of both SiCw and ZrO 2(2Y) particles are shown to be additive, but the addition of ZrO 2(2Y) particles decreases the strengthening effect of SiCw. The addition of SiCw can obviously improve the thermal shock resistance of Al 2O 3 and Al 2O 3 + ZrO 2(2Y) ceramics and the thermal shock resistance of Al 2O 3 + SiCw composites can be further improved by adding a few of ZrO 2(2Y) particles (10vol%).