DEFORMATION OF LEAD ALLOYS - AGING VS REC RYSTALLIZATION

Immediately after cold-rolling, non aged lead alloys exhibit a higher hardness. During the subsequent aging treatment at 20 degrees C the st ructure changes due to an recrystallization effect. The driving force of the transformation lies both in the oversaturation of the matrix an d in the cold work energy. The end result is the product of two mechan isms, a softening mechanism (recrystallization), and a hardening mecha nism (continuous or discontinuous transformation). Cold work always in duces an increase in transformation kinetics. Conversly, if rolling is performed after hardening, a slightly harder structure is obtained, B ut this hardness increase is very ephemeral. With high rolling ratios, recrystallization occurs during the rolling process. After static or dynamic recrystallization the final hardness is always lower than that of unrolled specimens.