A possible source mechanism for non-basal <c+a> slip dislocations was proposed which was based upon the formation of an attractive junction between glissile and sessile dislocations. The driving force for junction formation, which arose from long-range elastic interactions between c and a dislocations, was relatively large in most hexagonal close-packed metals. However, Be (with its unusually low Poisson ratio) was an exception. The cross-slip process was energetically unfavorable in Mg and Ti, from the viewpoint of a change in anisotropic elastic line tension, but it became favorable in Ti at temperatures above 300C.

Non-Basal Slip Systems in HCP Metals and Alloys - Source Mechanisms. M.H.Yoo, S.R.Agnew, J.R.Morris, K.M.Ho: Materials Science and Engineering A, 2001, 319-321, 87-92