Microstructure and fluidity of In-situ TiB₂/ZL205A composites

The in-situ TiB₂/ZL205A composites were prepared by the method of mixed salt reaction in aluminum alloy melt. The phases, morphology and distribution of TiB₂ particles and the fluidity of the fabricated composites were studied. The results show that the main phases of the TiB₂/ZL205A composites are α-Al, Al₂Cu and TiB₂. The TiB₂ particles with an average size of 500 nm and the shape of polygon or ovoid distribute mostly along the grains boundary and a few in the grains. The two relationships, that is the fluidity and casting temperature and the fluidity and mass fraction of Ti₂B particles, can all be described by the exponential damping model. When the casting temperature raises from 710℃ to 750℃, the fluidity of 7wt%TiB₂/ZL205A composites increases by 30.4%. When the casting temperature increases above 750℃, the increasing rate of the 7wt%TiB₂/ZL205A composites fluidity is decreased with the increasing of casting temperature. Compared with the matrix alloy, the fluidity of 3wt%TiB₂/ZL205A composites decreases by 21.8%, and the fluidity of 7wt%TiB₂/ZL205A composites decreases by 36.4%.