UC Davis

Solid solutions of TiB2-WB2 were densified and annealed simultaneously to cause the decomposition into the phases (Ti,W)B-2 and (W,Ti)B-2. Ni and Co were added to solid solutions formed by induction field activated combustion synthesis. The presence of these metals as additives markedly enhanced the kinetics of the subsequent decomposition process. With these additives, decomposition to the two phases occurred within minutes (360 s) in contrast to hours when the solutions did not include the additives. The phases resulting from decomposition, (Ti,W)B-2 and (W,Ti)B-2, were identified by X-ray to have the hexagonal AIB, and W2B5 structures, respectively. The precipitated phase, (W,Ti)B-2, occurred as elongated grains with aspect ratios of as high as about 10 in samples containing Ni as the additive.