Effects of high temperature mechanical damage on physical properties of unidirectional Ti/SiC metal matrix composite

A miniaturised test system was used to investigate how the thermal and electrical properties of a unidirectionally reinforced titanium alloy (Ti-6Al-4V)/SiC (SM114+) metal matrix composite change with mechanical damage at elevated temperature. Thermal conductivity and expansion measurements were obtained in the longitudinal and transverse direction both before and after short term strength and creep tests and at intervals during tests to assess changes in interface characteristics as functions of mechanical or thermal damage. The mechanical tests included monotonic stress-strain and ramp creep at temperatures between 500 and 650 degrees C. The changes in thermal properties were compared with model predictions for the dependence of thermal properties on interface characteristics. The agreement was good for thermal expansion changes but not for thermal conductivity. This was ascribed to the nature of the damage at the interface that probably still allowed thermal transport but not mechanical load transfer. MST/4668 (C) 2000 IoM Communications Ltd.