Deformation instability in crystalline alloys: Luders bands


A mechanism of localization of plastic deformation at high temperatures is investigated in the framework of the autowave model. A model of the formation and propagation of Luders bands is proposed. It is established that a Luders band is a wavefront of the plastic deformation rate. From this article's point of view, the conditions for the formation of a Luders band are decisive for the interpretation of the fluidity serration. The critical value of the deforming stress is determined, at which the homogeneous deformation becomes unstable with respect to the localized flow in the form of Luders bands. In the present consideration, we interpret the Luders band as a wave of switching of the plastic deformation rate. At low stresses, dislocations surrounded by clouds of impurity atoms move slowly and cannot provide a deformation comparable to that, which is produced by a testing machine. As the stress increases, the generation of "fast" dislocations begins, which are formed either due to the detachment of dislocations from the clouds of impurity atoms. As a result, this state, having arisen, propogates as a running front forming a shear band of "fast" dislocations.