Motion of screw dislocations under stress in a model B.C.C. lattice

Using a model b.c.c. lattice, the behaviour of the screw dislocation under various types of the shear stress at 0 °K has been investigated by computer simulation. The dislocation core moved in a zigzag way changing its slip plane alternately on two {110} planes so that the resultant slip trace was along the twinning {112} plane for every type of the shear stress. Calculated Peierls stresses were 0.0025, 0.0015, and 0.0027 μ for the shear on {110} plane, on {112} plane in the twinning direction, and on {112} plane in the anti-twinning direction, respectively, where μ is the shear modulus. These results agree semi-quanti-tatively with the experimental results on refractory b.c.c. metals at low temperatures, which indicates strongly that the plastic anisotropy in b.c.c. metals is the result of the characteristic behaviour of the screw dislocations in overcoming the Peierls potential.