Preparation Of In Situ TiB₂Particle Reinforced Aluminium Matrix Composites Of Good Purity-property

The in situ TiB2 particle reinforced aluminium matrix composites are widely used in automobile, aircraft, aerospace, chemical and other industries due to their high specific strength and excellent thermo-stability. In the various methods of preparation of in situ TiB2 particle reinforced aluminium matrix composites, the Flux-assisted synthesis (FAS) approach which involves the halide salt reactions is the most popular due to its simple process and low manufacturing cost.In this paper, the effects of different melt purification treatment on the microstructure and performance of in situ TiB2 particle reinforced aluminium matrix composites prepared by FAS were studied. The results showed that the Ar purification treatment can significantly impove the performance of TiB2 particle reinforced aluminium matrix composites and has very little influence on the content of TiB2 particles in the composites, in which the three kinds of purification treatment processincluding refining agent purification treatment, C2Cl6 purification treatment and Ar purification treatment. Compared with the pure aluminium, the ultimate tensile strength (UTS) of in situ TiB2 particle reinforced aluminium matirx composites prepared by the process of which adding the fluoride salt at 850℃, reacting for 55min at 850℃,then removing the residual salts, stirring for 90s at 240r/min speed, purifing by Ar for 10min at 0.5L/min, casting at 720℃ is increased by 166%. While its elongation decreases only by 7%.The further studies on the preparation of A14.5Cu1.1Si-xTiB2(x=0-4) composites via remelting and dilution process was carried out, i.e. the Al-5TiB2 master alloys were remelted and diluted by Al, Si and Cu according to the proportion of A14.5Cu1.1Si-xTiB2(x=0-4). And its enhancement mechanism was preliminarily analyzed. The results demonstrated that it is feasible to control the TiB2 content in the final composite by adjusting the proportions of addition during remelting and dilution process. Low content of TiB2 (4wt.%) in the composites can lead to a favorable strengthening effect. While the UTS of the A14.5Cu1.1Si-4TiB2 composites is 383 MPa in the heat-treatment state,38% higher than the A14.5Cu1.1Si alloy, its elongation is not changed significantly.In the A14.5Cu1.1Si-xTiB2 (x=0-4) composites, the fine grain strengthening, Orowan strengthening and CTE strengthening work together to reinforce the compositesso as to improve the performance.