Plastic Flow in bcc3He

The plastic flow in bcc 3 He was investigated by the same method as that used for hcp 4 He in a previous paper. The flow stress in bcc 3 He is smaller than that of hcp 4 He roughly by an order of magnitude. In contrast to hcp 4 He it is difficult to observe the yield drop at the initial stage of the plastic deformation in bcc 3 He. The observed results are analysed as shear flow of polycrystalline aggregates. At high strain rates the shear flow takes place by the operation of three pencil glide systems, and below a certain strain rate it proceeds by the pencil glide on two systems and climb of the dislocations of the systems. The strain rate dependence of the flow stress suggests that dislocations move at a constant velocity independent of the flow rate.