Tensile Behavior of SiC Fiber-Reinforced γ-TiAl Composites Prepared by Suction Casting

Abstract

The process of preparing SiC fiber-reinforced γ-TiAl composites by the conventional methods is difficult and complicated due to the high reactivity, high melting point and poor deformability of γ-TiAl alloys. In this work, suction casting, a promising method for preparing SiC_f/TiAl composite, had been attempted. In the process, γ-TiAl alloy melt was introduced rapidly into a mold within pre-arranged fibers that were coated with additional layer of titanium alloy. This simple method successfully prevented serious reactions between the alloy melt and the fibers which remained intact during the solidification process. The interfacial reaction layer was observed by optical microscopy, scanning electron microscopy (SEM). The interfacial reaction products were identified by transmission electron microscopy (TEM). Tensile tests of the matrix alloy and composites were performed at room temperature and 800 °C. The results exhibited that the tensile strength of SiC_f/γ-TiAl composite was higher than that of the matrix alloy at both room temperature and 800 °C. At room temperature, tensile strength of SiC_f/γ-TiAl composite was increased by about 7% (50 MPa), whereas a double increase in tensile strength 14% (100 MPa) was obtained at 800 °C. The titanium alloy coating on the fiber not only prevented the serious interfacial reaction between the γ-TiAl alloy melt and the SiC fiber, but also played a role in delaying the propagation of cracks in the matrix to the fiber at 800 °C. The fracture mechanism of the composite was analyzed by fracture metallographic analysis.