Effect of Thermal Exposure on the Interface Microstructure and Interfacial Shear Strength of the SiC Fiber Reinforced AlFe5Si2 Matrix Composite

The effect of high temperature on the interface microstructure and interfacial shear strength of the continuous SiC fiber reinforced AlFe5Si2 matrix (45 vol.% SiCf/AlFe5Si2) composite was investigated. The composite was prepared by hot isostatic pressing (HIP), and then thermally exposed at 260/300/350/400/450 °C for 20/50/100 h, respectively. The interfacial shear strength of the composite with and without thermal exposure was measured by push-out test. The interface microstructure and phase compositions of the composite with and without thermal exposure were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Results showed that the interfacial reaction took place at the interface between SiC fiber and aluminum matrix and formed Al4C3 phase during the preparation process. The activation energy of Al4C3 growth at the C/Al interface was about 163 kJ/mol. With increasing the thermal exposure temperature and time, the interfacial shear strength of the composite declined, especially at temperatures above 400 °C. The brittle Al3.21SiO0.47 compound formed at temperatures above 400 °C mainly resulted in the severe strength deterioration of the interfacial reaction zone.