The mechanical properties and microstructure of Al2O3/aluminum alloy composites fabricated by squeeze casting

Porous aluminum oxide (Al2O3) preforms were formed by sintering in air at 1200 °C for 2 h. A356, 6061, and 1050 aluminum alloys were infiltrated into the preforms in order to fabricate Al2O3/A356, Al2O3/6061, and Al2O3/1050 composites, respectively, with different volumes of aluminum alloy content by squeeze casting. The volume contents of aluminum alloy in the composites were 10–40 vol.%. For the corresponding composites, the hardness decreased dramatically from 610 to 213, 201, and 153 HV, the four-points bending strength of the composites increased from 397 to 443, 435.1, and 418.7 MPa, and the fracture toughness increased from 4.97 to 11.35, 11.15, and 10.98 MPa m1/2 of Al2O3/A356, Al2O3/6061, and Al2O3/1050 composites, respectively. From SEM microstructural analysis, the porous ratio and the relative density of the composites were the most important factors to affect the mechanical properties and the three different toughening mechanisms, i.e. crack bridging, crack deflection, and crack branching in the composites.