The Plastic Deformation of Pure Single Crystals of Lead and Copper

Single crystals of 99.999 percent pure lead and copper were grown by the Bridgman method. A tensile creep apparatus is described. Measurements on copper at 23°C and at −190°C show that for resolved shearing stresses below 0.6 kg per mm2 the steady-state creep rate is negligible (i.e., less than 10−6 per minute). The resolved yield stress for copper is 219±21 g per mm2 at both the temperatures used. In the case of lead, for resolved shearing stresses below 0.13 kg per mm2 the steady-state creep is negligible at −190°C. The yield stress at that temperature is 96±8 g per mm2. Measurements were made on the steady-state creep of lead at 25°C and 110°C. The results produced by annealing were investigated.