Characterization of Aging Behavior of Precipitates and Dislocations in Copper-based Alloys

The growth of precipitates in a deformed Cu Ni Si alloy with an aging treatment and the rearrangement of dislocations were investigated using X-ray scattering methods. A small angle X-ray scattering (SAXS) method was used for characterizing the growth behavior of the precipitates with aging. The results showed that the precipitates grew gradually to a few nanometers in radius in the alloy aged under the condition that the alloy exhibited a maximum of the hardness due to precipitation hardening. The growth rate was prompted by the onset of the over aging, where the hardness starts to decrease. The line profile analysis of copper diffractions using modified Williamson-Hall and modified Warren-Averbach procedures yielded a variation in the dislocation density of the alloy as a function of the aging time. The dislocation density of the alloy before the aging treatment was estimated to be 1.7 0 m, and its high value was held up to the peak-aging time. With the onset of the over aging, however, the dislocation density distinctly decreased by about one order, indicating that a large amount of the dislocation rearranged to release the alloy from the high dislocation-density state. It may be concluded that the massive rearrangement of dislocations was accompanied with coarsening of the precipitates.