Interface design in 3D-SiC/Al-Si-Mg interpenetrating composite fabricated by pressureless infiltration

Abstract 3D-SiC/Al-Si-Mg interpenetrating composites (IPCs) were fabricated by pressureless infiltration method. Interfaces in the 3D-SiC/Al-Si-Mg IPCs were modificated by using two different kinds of aluminum alloy Al-15Si-10Mg and Al-9Si-6Mg to infiltrate into 3D-SiC performs and different treated 3D-SiC preforms unoxidized or preoxidized in air at 1000 °C, 1100 °C and 1200 °C for 2 h respectively. Results showed that desired interfaces can be achieved in both IPCs made with those two aluminum alloys, as demonstrated by their excellent comprehensive properties. When the Al-15Si-10Mg alloy with excessive Si content is used for infiltration, interfaces in 3D-SiC/Al-Si-Mg IPC fabricated with the unoxidized 3D-SiC preform are directly bonded through atomic matching without any interfacial reaction and the composite has the properties of a thermal conductivity (TC) of 224.5 W/(m °C), a thermal expansion coefficient (CTE) (RT ~ 300 °C) of 7.04 × 10 −6 /°C and a bending strength (BS) of 277 MPa. When the Al-9Si-6Mg alloy with a lower Si content is used for infiltration, interface zone with a thickness around 200 nm forms in the 3D-SiC/Al-Si-Mg IPC fabricated with the 3D-SiC preform preoxidized at 1000 °C. The reaction-bonded interface is composed of AlN and MgAl 2 O 4 which have better interface affinity with SiC and can isolate SiC effectively from liquid Al against the formation of detrimental Al 4 C 3 phase. The composite has the properties of a TC of 219.5 W/(m °C), a CTE (RT ~ 300 °C) of 7.66 × 10 −6 /°C and a BS of 318 MPa.