Development of Slip Bands in Single Crystals of Titanium and Its Alloys at 4.2 - 423 K

Abstract

The morphology and peculiarities of the surface traces of prismatic slip were studied on single crystals of titanium of different purity and the Ti-5.3% Al alloy, which were compressed at 4.2-423K. In titanium the quantitative parameters of slip bands and their formation at the temperature corresponding to an alteration of the rate controlling mechanisms and depending on the interstitial impurity concentration are observed to change essentially. At low temperatures the development of slip bands is governed by the motion of screw dislocations of the same sign generated by the near-surface sources. At higher temperatures slip bands are approximated by two groups of dislocations at both sides of the source. It is assumed that the structure of screw dislocation cores split simultaneously in the prism and pyramid planes plays a more important role in the plastic deformation of the Ti-5.3% Al alloy than to that of titanium. The slip takes place by means of the repeated sessile-glissile transformation of screw dislocations. The branchy character of slip is accounted for by the hindered thermally activated blocking-out of dislocations in the primary planes and by the possibility of transitions between different planes; as a result, their way consists of {1010} and {1011} portions.