On the Aging Process of Cu-Fe Alloy

Abstract

Precipitation processes during isothermal aging and step-annealing of Cu-2.46, 0.99. 0.52%Fe alloys were investigated mainly by electrical resistivity measurement, hardness test and transmission electron microscopy.
The principal results obtained were as follows:
(1) The clustering or precipitation reaction occured during quenching were drastic, especially in the alloy of high Fe content. (2) The anomalous electrical resistivity increase due to reversion of quenching clusters was observed during the isothermal aging of 0.52%Fe alloy at relatively high temperatures. The resistivity increment increased as the aging and solution temperatures rised, the quenching rate slowed down and the size of specimens became larger. (3) The precipitation process during step-annealing were sub-divided into two stages by an intermediate reversion process of clusters. The apparent activation energy for the initial precipitation in 2.46%Fe alloy was 216 kJ/mol and nearly equal to that for impurity diffusion of Fe in copper. The energy was lowered as Fe content decreased. (4) The growth of γ-Fe particles was expressed by the t^1⁄3 law of Ostwald ripening after completion of precipitation. The coherency contrast of spherical γ-Fe particles was still maintained even under the complete over-aging condition.