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 MgAl2O4 which have better interface affinity with SiC and can isolate SiC effectively from liquid Al against the formation of detrimental Al4C3 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.