High Temperature Creep Behavior Of In Situ TiCp/LD7 Aluminum Matrix Composite

The creep behavior of LD7 Al alloy and in situ TiCP/LD7Al composites (with 15% and 20% volume fraction of TiC particles respectively) was investigated under a condition of constant compressive stress at 523, 573 and 623 K, respectively.The results showed that both the stress exponent and the apparent activation energy of the composite were higher than these of LD7 Al alloy, indicating that the existence of TiC particles significantly improved the high-temperature creep property of LD7Al alloy. By introducing a threshold stress, the creep results of the higher stress exponent and apparent activation energy in the composites can be explained well; Both the calculation based on the Orowan dislocation model through the introduction of the threshold stress concept and the normalization of the creep data showed that the high-temperature creep behavior of the composites could be explained by the dislocation climb mechanism; The threshold stress can originate from the resistance of TiC particles to the deformation of the matrix and the resistance and pinning of the precipitated S(Al2MgCu) phases to the dislocation. The threshold stress was also related to the interaction between the load transferred to TiC particles and the discontinuous long range internal back stresses caused by creep; The matrix structure can be changed by introducting TiC particles, which have the effect of the grain refinement. It is an important factor that the composites have the stronger creep resistance.