Dislocation motion and multiplication in Cu-Ni single crystals

For Cu-2 and 5% Ni single crystals by pulse loading and double etching the stress dependences of the breakaway of grown-in dislocations, of the velocity of freshly multiplied dislocation, and of the multiplication of fresh dislocations are obtained. Only the latter clearly correlates with the critical resolved shear stress (CRSS) observed in macroscopic tensile experiments. Also the comparison of the parameters of the rate-controlling processes as determined from microscopic and macroscopic measurements indicates that the CRSS in the concentrated alloys is governed by the transfer process of slip into new slip planes rather than by simple movement of dislocations across the obstacle field. Between 2 and 5% Ni the slip pattern changes from a rather homogeneous to a heterogeneous one. This is discussed in terms of blocking of dislocation sources and change of obstacle structure by dislocations.