Interfacial stability and mechanical properties of Al₂O₃ fiber reinforced Ti matrix composites

Abstract

The mechanical properties of the interfaces in an Al₂O₃ fiber reinforced β-21S Ti alloy have been evaluated by using fiber pushout tests. The Al₂O₃ fibers were coated with a refractory metal and Y₂O₃ which served as a diffusion barrier during the HI** used to produce the metal matrix composites. By doing fiber pushout tests, the interfacial fracture was found to occur at the interface between the refractory metal and the Y₂O₃. The interfacial shear strength and interfacial frictional stress were measured to be 323 and 312 ± 2 MPa, respectively. The interfacial frictional stress, which is due to asperity interlocking during the fiber sliding, was correlated to the surface roughness of the coated Al₂O₃ fiber obtained with the aid of an atomic force microscope. The measured surface roughness of 18.8 ± 2.2 nm was related to the frictional stress through Hutchinson’s model.⁹ The frictional coefficient between the Al₂O₃ fiber and the Ti matrix is calculated to be 0.32 ± 0.02.