DISCONTINUOUS PRECIPITATION IN Co-3wt. % Ti-2wt. % Fe ALLOY.

Discontinuous precipitation in Co-3 wt. % Ti-2 wt. % Fe alloy has been studied using the techniques of optical, scanning, and transmission electron microscopy in the temperature range of 773 to 973 K. The interlamellar spacing and the displacement of the reaction front were systematically evaluated utilizing statistical techniques at various aging temperatures and times. It was shown that at a fixed temperature, the interlamellar spacing was independent of the aging time, while the displacement varied linearly with time. The variation of the reciprocal of the interlamellar spacing with the aging temperature indicated that an upper limit (approx. 926 K) existed for the occurrence of discontinuous precipitation in Co-3 wt. % Ti-2 wt. % Fe. The interface displacement data in conjunction with Turnbull's model led to an activation energy of 234 kj/mol, which indicates that the reaction occurred through a grain boundary diffusion mechanism.