Superior creep resistance of 0.3Â wt% nano-sized TiCp/Al-Cu composite

The creep resistance of Al-Cu alloys deteriorates significantly at high temperatures owing to the coarsening of θ′ precipitates during creep, which limits their applications at elevated temperatures. We fabricated a cast Al-Cu matrix composite containing finer and denser θ′ precipitates by adding 0.3 wt% in situ nano-sized TiCp into an Al-Cu alloy. The steady creep rates of the nano-sized TiCp/Al-Cu composite were 3-17 times lower than those of the Al-Cu matrix alloy at 453-493 K under applied stresses of 120-200 MPa, respectively, which was attributed to the higher threshold stresses of the composite due to the strengthening effect of the nano-sized TiCp and the larger number of θ′ precipitates with smaller diameters. The accelerated coarsening of θ′ precipitates after higher temperature creep could contribute to the decrease of threshold stress with increasing temperature. The analysis of the true stress exponent indicates that the dislocation climb mechanism is dominant in both the matrix alloy and the composite during creep.