Effect of Ball Milling Process on the in Situ Synthesis of Nano-TiB Whiskers

Ball milling process has an important effect on the microstructure and the morphology of final powder products and the corresponding as-sintered samples. In the present study, Ti-7Al-0.2B (wt%) mixed powder was ball-milled by low-energy and high-energy types of ball mills, and then the milled powder was sintered by hot-pressing. On this basis, the morphology evolution of the powder was analyzed, and the microstructures of the reinforcements in the as-sintered composite were investigated. Research results show that in the low-energy ball milling process, mechanical alloying occurs between the powder particles. TiB whiskers formed in sintering process are long and thin without linked coarse crystals bars or clusters. Under the high-energy milling, the average particle size of the powder is refined remarkably to 1 μm, and Ti(Al) supersaturated solid solution or even amorphous structure is formed during the milling process. In the following sintering process, nano-scale TiB whiskers are synthesized and they are uniformly distributed in the matrix.