Annealing and Precipitation in Iron–1.23 wt.-% Copper

Abstract

Structural changes occurring during annealing and precipitation in cold-worked iron–1.23 wt.-% copper have been followed by transmission electron micro-scopy. After recovery at 600° C spherical precipitates are observed on dislocations and at sub-boundaries, the size and distribution of precipitates being related to the dislocation density and size of individual sub-grains. Growth of precipitate particles is thought to be assisted by mobile line and planar defects acting as collectors. On annealing at 750° C with a slow heating rate, the time for complete recrystallization is greater than when the heating rate is rapid owing to atmosphere locking of dislocations. The heating rate has a marked effect on the shape of precipitates, slow heating producing spheres while fast heating, in which less precipitate growth occurs when substructures are present, results in rods.