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 'damag e'. Annealing is employed to restore the plasticity margin and thus to avoid damage. The exhaustion of the fatigue life of machine parts pro duced by deformation processes is also accompanied by such micro-disco ntinuities. 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 fati gue strength (low or zero damage) achieved by conventional heat-treatm ent and unconventional heat-treatment, i.e. heating under tri-axial co mpression, is reported. Experimental data indicative of the healing of micro-damage in some metals are adduced. Practical recommendations ar e given. (C) 1998 Elsevier Science S.A.