Influence of external stress on discontinuous precipitation behavior in a Cu-Ag alloy

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The influence of an applied stress on discontinuous precipitation (DP) has been nvestigated for a Cu-5 wt pct Ag alloy aged at 573 K. A tensile stress enhances the growth of DP cells in both the loading direction (LD) and transverse direction (TD), but the cell growth rate in the TD, vCT, is faster than that in the LD, vCL. A compressive stress suppresses the cell growth in the TD, but does not significantly influence it in the LD. The tensile or compressive stress tends to produce discontinuous silver precipitates elongated in a h110ia direction of the copper matrix in a DP cell, nearly perpendicular to or parallel to the LD. This result, along with the dependence of the cell growth rate on the sense of the applied stress, can be understood through the interaction energy between the external stress and the misfit strains of silver precipitates. An analysis of length-change easurement results has enabled estimation of the ratio of the growth rate of silver precipitates in the TD, vPT, to that in the LD, vPL, under tension or compression. The estimated values of vPT/vPL are in good agreement with the values of vCT/vCL, experimentally obtained, indicating that the anisotropy of the cell growth rate is determined by the growth behavior of silver recipitates. © The Minerals, Metals & Materials Society and ASM International 2010.