Quenched-in stresses in FeCu(5%) alloy

Abstract

Quenched-in internal stresses have been determined in precipitated Cu grains in FeCu(5%) alloy as a function of the quenching temperature. The (1 1 1) reflection of Cu was considered, with attention paid to the line broadening. Significant differences are recognized in the developing stresses in the range of 850–200°C quenching temperature. The Cu grains are under tension in increasing degree with the quenching temperature. The line broadening also shows a peculiar behaviour in this temperature region. In contrast with the elastic stresses determined from the peak shift, these changes can be connected to plastic stresses or to the excess precipitations that gradually appear below the solubility limit of Cu in Fe. During the homogenizing treatment (850°C, 3 h) only the Cu amount above the solubility limit precipitates on the grain boundaries of the Fe grains. At lower temperature further Cu precipitates, but within the grains. These new and growing Cu grains with sizes up to ∼1–2 μm contribute to the line broadening. These two processes, precipitation of Cu on the grain boundaries and within the grains, are responsible for the peculiarity of the broadening.