Microstructure and mechanical behavior of Al-TiAl3 composites containing high content uniform dispersion of TiAl3 particles

The microstructure, mechanical behavior and deformation mechanisms of Al-TiAl3 composites containing a wide range of volume fraction of TiAl3 (V-p: 24.6-89.0%) with uniform distribution were investigated. Microhardness and strength of the composites increase with increasing V-p of TiAl3 particles, reaching similar to 11.0 times and similar to 8.0 times those of the matrix respectively. While the strength of the composites can be correlated well to the comprehensive contributions of various strengthening mechanisms of the matrix for low V-p, that for high V-p was found to fit to direct contributions from both the matrix and particle following the law of mixture. Besides the deformation of the matrix, evident plastic deformation of TiAl3 particles by dislocation activities as well as twinning was observed in the composites upon loading at room temperature. Two mechanisms for crack initiation inside the TiAl3 particle were identified, namely by intersection of twins and by interaction between dislocations and twins. Microcracks tend to propagate along the twin boundaries in TiAl3 particles and were found to be suspended at the particle/matrix interface. The unique deformation behavior of TiAl3 particles in the composites can be attributed to the uniform distribution of TiAl3 particles that ensures a continuous network of surrounding matrix even at very high V-p.