The restoration of the margin of metal plasticity after cold deformation

Cold plastic deformation of metals is accompanied by the appearance of discontinuities on the micro-level, hereinafter referred to as `damage'. Annealing is employed to restore the plasticity margin and thus to avoid damage. The exhaustion of the fatigue life of machine parts produced by deformation processes is also accompanied by such micro-discontinuities. Unfortunately, however, methods for increasing the fatigue life of such machine parts by a treatment that can restore the metal properties degraded during their production are not widely applied. In this paper a more intensive restoration of plasticity margin and fatigue strength (low or zero damage) achieved by conventional heat-treatment and unconventional heat-treatment, i.e. heating under tri-axial compression, is reported. Experimental data indicative of the healing of micro-damage in some metals are adduced. Practical recommendations are given.