Preparation and microstructure evolution of TiB₂/Al composite powders by gas atomization method

The TiB₂/Al composite ingot was prepared by the fluoride salt reaction method, and the TiB₂/Al composite powders were prepared by the high pressure gas atomization. The structures and properties of the composite ingot and powders were characterized by metallographic microscope, scanning electron microscope, X-ray diffractometer, and particle size distribution instrument. The results demonstrate that, the solubility product of TiB₂ in Al melt is much smaller than that of the TiAl₃ and AlB₂ phases in the experiment condition, the change of Gibbs free energy caused by the precipitation of TiB₂ from Al melt is more negative than that caused by the precipitation of TiAl₃ or AlB₂ from Al melt. The TiB₂/Al composite ingot and powders are mainly composed of α-Al matrix and TiB₂ phase. The TiB₂ particles in the TiB₂/Al composite powders prepared by gas atomization have nano-scale, and uniformly disperse in the Al matrix, no obvious segregation phenomenon is observed. The size distribution of the TiB₂/Al composite powders exhibits a normal state in the range of 10~100 μm. The powder yield with the particle size between 10~70 μm is 81.1%, the yield for the particle larger than 70 μm is 12.6%, and that less than 10 μm is 6.3%.