Koji Tanoue1, Junichi Ishimaru2, Yoshihiro Takahara1 and Hidehiko Matsuda1
1Department of Metal Processing Engineering, Kyushu Institute of Technology, Kitakyushu
Measurements of the electrical resistivity and stress relaxation tests are made to clarify whether the two rate-controlling processes of the dislocation intersection and the shearing of GP zones by dislocations operate in parallel (parallel processes) or consecutively in series (consecutive processes) when Al-Zn alloys are plastically deformed at 77 K. The discrimination between parallel and consecutive processes is done by investigating the sign of dm*/dσ * derived from the assumption that the strain rates during stress relaxation depend on the effective stress in the same way as the Johnston-Gilman type equation of \dotε ∝ σ *m^*. All of the deformation belongs apparently to parallel processes except that the single process of the dislocation intersection rate-controlls the deformation in a dilute alloy with no maximum of electrical resistivity at the initial ageing and in any alloys at the final one. The single process changes to consecutive processes at about the stress level for deformation stagnancy after a full relaxation. This transition indicates the possibility that there exist small GP zones even in a dilute alloy or at the final stage of ageing.
rate-controlling process, parallel and consecutive processes, low temperature deformation, stress relaxation, aluminum-zinc alloys
Please do not copy without permission.