Effect of copper addition and heat treatment on the depth dependence of the nanoindentation creep of aluminum at 300 K

Constant-load indentation creep tests were performed on pure aluminum and aluminum 4wt% copper at 300K to assess the influence of indentation depth, copper addition, and heat treatment upon the indentation creep rate. The stress dependence of the average indentation creep rate could be expressed for all the samples tested in terms of a mechanism of obstacle-limited dislocation glide. The calculated activation energy showed the same dependence upon indentation stress for all the conditions investigated. We therefore conclude that the indentation creep rate is limited by dislocation/dislocation interactions regardless of indentation depth, copper addition, or heat treatment. The presence of 4 wt% copper and heat treatment, however changes, the dislocation density, and hence the spacing of the dislocation-dislocation interactions. (C) 2008 Elsevier B.V. All rights reserved.