Microstructures And Properties Of TiC/7075composites Produced By In-situ Synthesis Research

Particle reinforced aluminium matrix composites have caused wide public concern as the ideal automobile lightweighting materials. In this paper, in-situ synthesis was used to fabricate the Ti C and Al3 Ti particulate reinforced wrought aluminium alloy 7075 matrix composite. Through the organization analysis and performance test of composites we study the mechanism that particle influence of the microstructures and mechanical properties of composites. The wear performance and wear mechanism as well as the materials fracture behavior and fracture mechanism were studied identically.In-situ Ti C reinforced 7075 composites have been synthesised by adding the Al-Ti-C powder blocks into molten 7075 alloy. The investigation of this process shows that co-presence of Al3 Ti blocks with Ti C particles was found in the composites at the melt temperature 800 ℃, but only Ti C particles occurred in the composites when the melt temperature come to 1100℃. In addition, adding the Al-Ti power blocks into molten 7075 alloy could form Al3 Ti particles reinforce composite.The main work of this study is focus on the effect of addition of Ti C and Al3 Ti particles on the microstructures and mechanical properties of composites. The formation of Ti C particles in the matrix resulted in the refinement of as-cast microstructures, improved the strength of the composites at ambient temperature and the strength of the composites increased with the increased of Ti C percentage, though the addition of Ti C reduce the ductility of composites. The formation of Al3 Ti particles in the matrix resulted in the refinement of as-cast microstructures, improved the strength of the composites at ambient temperature and the strength of the composites increased with the increased of Al3 Ti percentage, though the addition of Al3 Ti reduce the ductility of composites heavily. The strength of Ti C/7075 composites and Al3Ti/7075 composites increased due to grain refining strengthening, dislocation strengthening and dispersion strengthening. SEM observation of the fracture of 7075 alloy and Ti C/7075 composites show that the fracture surface of the two kinds of materials above were ductile dimple at ambient temperature which indicate that Ti C did not change of fracture mechanism. However, Ti C particles made dimple finer and more than that of 7075 alloy, which fit to the decrease ductility of composites. SEM observation of the fracture of Al3Ti/7075 composites show that the fracture surface of the materials was quasi-cleavage fracture.The study on the sliding wear behavior of Ti C/7075 composites and Al3Ti/7075 composites showed that the wear resistance of both composites are notable superior to that of 7075 matrix alloy and are greatly enhanced with the increase of particles volume fraction. The SEM of wear surface revealed that the wear mechanism of both7075 alloy and composites including adhesive wear and grinding-particle abrasive wear.