MECHANICAL ALLOYING PROCESS OF METAL-B (M=TI, ZR) POWDER MIXTURE

A mixture of metal and boron powders (M = B = 1:2; M = Ti, Zr) was milled using a vibratory ball mill with steel balls of various sizes. During milling, the temperature of the mill container was measured with a thermocouple attached to the surface of the container. In the milling of the Ti-B powder mixture, an exothermic temperature spike was observed during milling and fine TiB2 particles were formed right after the spike when milling with balls of 19.1 mm or more. It was found that the ball size affects both the milling time until start of the spike and its magnitude. On the contrary, no temperature spike was observed when milling with balls of 17.5 mm or less. The temperature spike suggests the occurrence of a combustion synthesis reaction. In the milling of the Zr-B mixture, no temperature spike was observed even when milling with 25.4 mm balls.