On the Strengthening Mechanism in Neutron Irradiated Copper Single Crystals. I. On Experiments Concerning Strain Rate Changes Critical Comments on the Preceding Paper of T. J. Koppenaal and R. J. Arsenault

Strain rate changes are used for analysing the flow stress of n‐irradiated copper crystals and lead to the following conclusions: a) The “active crystal length”, i. e. the number of simultaneously active slip planes, increases with the strain rate \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma $\end{document} , resulting in \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma $\end{document} not being proportional to ⋖ (cross‐head speed) [1]. b) The critical shear stress (css) varies with ⋖ more rapidly than is expected from theory [2]. In the preceding paper [3] arguments are advanced against both of these statements. All of these arguments will be invalidated. The proportionality \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma $\end{document} ∼ ⋖ is shown to represent a rather special case from an atomic point of view. By far more general is a non‐proportionality \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma $\end{document} ≁ ⋖. Taking this into accont one succeeds in describing straightforwardly the results of b). New experiments supporting our former statements are going to be reported. All conclusions drawn previously [4, 5, 6] on the strengthening mechanism in copper and based on a) and b) can be fully maintained [7].