Lamellar-interpenetrated Al-Si Mg/Al2O3-ZrO2 composites prepared by freeze casting and pressureless infiltration

Using freeze casting and pressureless infiltration methods, we prepared lamellar Al-Si-Mg/Al2O3-ZrO2 composites with initial ceramic loading of 30 vol% and different Al2O3:ZrO2 weight ratios (Al2O3:ZrO2=1:9, 3:7, 5:5, 7:3 and 9:1). The resultant composites inherited the lamellar structure of the Al2O3-ZrO2 scaffolds, and the thickness of both metal and ceramic layers showed a trend of first increase and then decrease with increasing Al2O3 content. During pressureless infiltration, multiple chemical reactions took place between ZrO2 and the Al-12Si-10Mg alloy and the main reaction products were (Al1-m, Si-m)(3)Zr, Al2O3 and ZrSi2 phases. The degree of the reaction depended on the ZrO2 content in the ceramic composition. In general, the compressive strength of the composites decreased with increasing Al2O3 content, but three-point bending strength showed a first decrease and then increase. When Al2O3:ZrO2=1:9, the compressive and bending strength of the composites reached about 997 +/- 60 MPa and 426 +/- 10 MPa, respectively. A simple model was proposed to illustrate the fracture mode and toughening mechanism of the composites.