Laves Phase Formation in the Fe20Co18W Alloy Annealed at 800°C

Abstract

The precipitation behaviour of the Fe20Co18W (wt%) alloy was studied by transmission electron microscopy during aging treatments at 800°C. The decomposition of the matrix produces the C14 phase. At the beginning of the heat treatment, the observation at the atom scale indicates that the structure of the precipitates does not coincide exactly with the Laves phase. Using the orientation relationship between the Fe based matrix and the precipitates it is shown that simple atomic shifts can lead to the transformation from the bcc matrix to the C14 Laves phase.

Precipitation and age-hardening in the Fe–27Co–8Mo alloy

“…Owing to the measured composition of the precipitates, the change in lattice parameters cannot be related to a change in Co or Mo content. Such a small deviation of the lattice parameters was already observed for the l phase in the Fe20Co18W alloy [41]. On the basis of the literature on l or m phases, the slightly different lattice parameters, already noticed at 660 C, can be attributed to the disordered state of the crystals when annealing at a low temperature.…”