時効後強圧延した銅-2.3%鉄合金の焼鈍による軟化挙動について

Abstract

A solution-treated specimen and four kinds of aged specimens of Cu-2.3 wt%Fe alloy, containing spherical coherent precipitates with smaller diameters than 430 Å, were cold-rolled 93.3%. The effects of the precipitate particles on the softening behaviour during isochronal annealing were studied by hardness measurement, and optical and transmission electron microscopy. The results obtained were summarized as follows. The hardness of this alloy increases remarkably and non-ferromagnetic γ-precipitates in the aged specimens transform to a ferromagnetic α-phase and lose coherency with the matrix by 93.3% cold-rolling.The softening of the aged specimens proceed gradually during annealing after rolling and the softening rates were much slower than that of the solution-treated specimen. The temperatures for 50% hardness drop in the aged specimens were higher than that of the solution-treated specimen by about 410°∼470°C.The differences of the softening rates among the aged specimens are small, but the softening rate of the specimen containing precipitate particles with a diameter of about 430 Å, is lower than that of the other specimens.The formation and the growth of recrystallization nuclei during annealing in the aged and rolled specimens proceed preferentially in the area with no or a few precipitate particles.It appears that the precipitate particles in the aged and rolled specimens retard the movement of dislocations, subgrain boundaries, recrystallized grain boundaries and old grain boundaries in the process of recovery and recrystallization.Recovery and recrystallization of the solution-treated and rolled specimen during annealing almost complete before precipitate particles come to reveal a retardation effect.