Stress relaxation in cobalt between 15 and 300 K

Abstract

The slope of the logarithmic stress–relaxation curve for a well-annealed cobalt polycrystal of 99·999% purity has been measured as a function of the initial stress level from which relaxation at constant strain was allowed to start at a given temperature between 15 and 300 K. A pronounced undulation was observed in the plot of the relation between the inverse of the stress sensitivity of the relaxation rate and temperature, with a maximum and a minimum at about 75 and 50 K, respectively. The ‘classically unexpected’ behaviour below about 80 K seems to arise from the progressive inhibition of dynamic recovery process as T→0 K, which necessitates the use of stresses higher than that applied in the basic equations describing the mode of deformation.