Quenching effect on creep of polycrystal nickel at 1.5-4.2 K

Stepwise creep of vacuum-remelted nickel of 99.996% purity at temperatures of 1.5; 2.2 and 4.2 K in the initial and hardened state was studied. It has been established that excess concentration of vacancies reduced the creep rate, especially at low applied stresses (sigma < 0.4 sigmasub(B)) due to the increased number of barriers controlling the motion of dislocations in this temperature range. As the stress applied increases, this difference reduces, and at sigma > 0.4 sigmasub(B) (T=const) the creep characteristics only slightly depend on the specimen prehistory. The creep of hardened and initial specimens in the investigated temperature range is of an athermal nature up to sigma <= 0.8 sigmasub(B), but at higher stresses an increase in temperature from 1.5 to 4.2 K increases the rate of nonstationary creep of both initial and hardened specimens. The causes for the regularities observed are discussed