Creep rupture of [90]8 Sigma fibre reinforced titanium matrix composite

The transverse creep rupture of Ti–6-4, reinforced with Sigma SM1140+ SiC fibre, has been studied at 450 and 600°C. In all cases the rupture lives are found to be lower than for the monolithic Ti–6-4 alloy. At 450°C in the high/medium stress regime, where interfaces fail on load-up, intergranular failure of the matrix occurs. This is caused by oxidation damage and its severity increases as the rupture time increases. At low stress, however, where interfaces do not fail on load-up, intergranular failure is reduced due to the lack of an easy oxygen diffusion path. At 600°C, fracture surfaces from the high/medium stress regime do not exhibit the intergranular failure observed at 450°C. At low applied stress at 600°C, however, the TMC exhibits signs of severe oxidation damage in the form of attacked fibre/matrix interfaces and brittle matrix failure. Previously developed TMC creep rupture models have been assessed. The Wright-Crossman model is found to provide a good upper bound on the experimental data whilst the more recent John-Khobaib-Smith model provides a lower bound.