The effect of solute additions on the steady-state creep behavior of dispersion-strengthened aluminum
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Abstract
The effect of solute additions on the steady-state creep behavior of coarse-grained dispersionstrengthened aluminum alloys was studied. Recrystallized dispersion-strengthened solid solutions were found to have stress and temperature sensitivities quite unlike those observed in single-phase solid solutions having the same composition and grain size. The addition of magnesium or copper to the matrix of a recrystallized dispersion-strengthened aluminum causes a decrease in the steady-state creep rate which is much smaller than that caused by similar amounts of solute in single-phase solid solutions. All alloys exhibited essentially a 4.0 power stress exponent in agreement with the model of Ansell and Weertman. This was observed even in alloys whose matrix shows a much lower stress exponent when tested as a single-phase solid solution. The activation energy for steady-state creep in dispersion-strengthened Al−Mg alloys, as well as the stress dependence, was in agreement with the physical model of dislocation climb over the dispersed particles. For the dispersion-strengthened Al−Cu alloys, the activation energy for steady-state creep suggested that the kinetics of dislocation climb may be related to the mobility of copper'atoms in the matrix. Electron microscopic examination of the dislocation structure present after steady-state creep had been reached suggested that few mobile dislocations are involved in the steady-state creep process at the stress levels employed in this investigation.
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