| Popis: |
The structural features associated with easy glide in high-purity aluminum crystals have been studied by microscopic and X-ray methods. The temperature dependence of the phenonemon has been examined on identically oriented crystals over the range − 196°C to 200°C, while the influence of specimen-length has been studied at room temperature. An examination of the orientation dependence of the stress-strain curves of copper single crystals confirms the results of Rosi in so far as easy glide ends at a value of the resolved shear stress σ0 such that σ0 − τc (critical resolved shear stress) is constant. However, it is shown that the length of the easy-glide range varies because of the existence of a size factor, demonstrated by experiments on crystals of identical orientation, but of different sizes. The effect of thin electro-deposits and, in particular, of alloying additions on the extent of easy glide, has been investigated. The view is advanced that easy glide ends as a result of secondary slip arising prematurely in the vicinity of dislocation pile-ups. Examination of this model gives the result that τcσ0 is constant, in accord with the experimental results. The value of τc determines the extent of easy glide, and from this follows an explanation of the temperature dependence. Variation in the length of the slip path and consequently of the number of pile-ups, is put forward as an explanation of the orientation dependence of the phenomenon. |
