Deformation Mechanisms of Alpha-Uranium Single Crystals

The operative deformation elements in α-uranium single crystals under compression at room temperature have been determined as a function of the compression directions. The deformation mechanisms noted may be arranged with respect to their frequency of occurrence and ease of operation in the following order: 1—(010)-100] slip, 2—{130} twinning, 3—{~172} twinning, and 4—under special conditions of stress application, kinking, cross-slip, {~176} twinning, and {011} slip. The composition planes of the {172} and {176} systems were found to be irrational. Cross-slip was shown to be associated with the major (010) slip system, coupled with localized interaction of slip on the (001) planes. The mechanism of kinking was found to be similar to that observed in other metals in that it occurred chiefly when the compression direction was nearly parallel to the principal slip direction 100] and was associated with a lattice rotation about an axis contained in the slip plane and normal to the slip direction: the 001] in the uranium lattice. The resolved critical shear stress for slip on the (010)-100] system was found to be 0.34 kg per mm². In a single test it was shown that under compression in suitable directions twinning on the {130} also occurs at 600°C