Effect of external stress on discontinuous precipitation in a Cu–2.1 wt % Be alloy

Abstract

The influence of an applied stress on discontinuous precipitation (DP) in a Cu-2.1wt%Be alloy aged at 300ºC has been examined. A compressive stress accelerates the growth of DP cells, consisting of lamellae of the precipitated γ phase and the solute-depleted α phase, but a tensile stress does not essentially change it. The cell growth rates along the loading direction under the compressive and tensile stress are identical to those along the direction perpendicular to the loading direction under the same. Both the compressive and tensile stress have no influence on the incubation time to initiate DP. From measurements of the specimen length-change and investigations of the distribution of γ variants in cells in a particular case, specific γ variants among crystallographically equivalent ones are found to be formed, depending on the sense of the applied stress. This result, together with the dependence of the cell growth rate on the sense of the applied stress, can be well understood through the interaction energy between the external stress and the misfit strains of discontinuous γ precipitates.

Tensile-stress-induced growth of ellipsoidal ω-precipitates in a Ti–20wt%Mo alloy

“…These results indicate that the creep strain due to dislocation motion does not contribute to the length change. The specimen 12 length-change ε T along any direction can be represented as functions of the average misfit strain along a direction caused by the misfit strains of precipitates along the direction, the volume fraction f of the precipitates, and the dimensional change due to the change in solute atoms in the solid solution [11,15].…”

“…2 and 3, in a diffusion-controlled reaction, a linear dimension of the growing product region is proportional to the square root of the growth time, whereas, in 15 an interface-controlled reaction, it is linearly proportional to the time. Thus, an interfacecontrolled boundary of a very small product region may become diffusion-controlled as the region grows larger [16].…”

The effect of aging process on the microstructure and mechanical properties of a Cu–Be–Co–Ni alloy

“…During the NA process, the alloy was maintained at an elevated temperature (aging at 320°C for 180 min). According to Monzen et al [18], precipitates in the Cu-Be-Co-Ni alloy tended to nucleate at the grain boundaries of α phase (solid solution phase). When the alloy reaches the peak aging, those grain boundary precipitates have already coarsened due to the Ostwald ripening [19].…”

Recent Developments on Discontinuous Precipitation

“…The influence of applied stress on the DP reaction in a Cu-2.1wt % Be alloy aged at 300°C was examined by Monzen et al [40]. A compressive stress accelerated the growth of DP cells, which consisted of lamellae of the new γ phase and the solute-depleted α phase, but a tensile stress did not essentially change it.…”