Investigation of high-temperature plastic deformation using instrumented microindentation tests. Part IThe deformation of three aluminum alloys at 473 K to 833 K

Constant-load indentation tests were performed on wrought-2024, P/M-2024, and wrought-1100 aluminum alloys to assess the capability of the microindentation testing technique for measuring the high-temperature deformation rate controlling parameters of these alloys. The three alloys all display threshold indentation stress σ_th below which the indentation strain rate ε_ind approaches zero. The nominal inter-obstacle spacing, ℓ*, calculated from σ_th, increases with temperature in a way that is consistent with the known temperature dependence of the inter-particle spacing and dislocation cell size. The measured activation energy ΔG_o of ɛ_ind increases with temperature but remains within the range that is typical of deformation that occurs by dislocation glide limited by weak particles or dislocation/dislocation interactions. The three alloys tested show different trends of ΔG_o versus ℓ* and the trends are consistent with the known temperature dependence of the obstacles to dislocation glide. This study demonstrates that high-temperature indentation tests are sufficiently precise to detect changes in the operative deformation parameters between different alloys of the same general composition. This lays the groundwork for the use of this technique as a general tool for studying the local high-temperature deformation of a wide range of metal-based systems.