Release of stored energy during low temperature annealing of some cold worked metals

Abstract

Recovery processes have been studied by measuring the release of stored energy in Cu, Ni, Ag and Au during annealing in the temperature range of stages II and III after deformation at − 195°C. Stage II recovery shows a fine structure, somewhat different for the different metals. In Cu and Ag, the energy released is about 2 per cent of the work done during deformation, practically independent of the degree of cold-work (40–70 per cent compression). Within the accuracy of the measurements (0.2 per cent) no influence of the annealing processes on the lattice specific heat could be observed. Comparison of the energy released to the decrease of electrical resistivity during annealing in stages II and III results in a value of the stored-energy/resistivity ratio for these stages: U Δ ϱ = 3.0–3.5 cal/g μΩcm . The influence of impurities (0.1 and 1 at.% Au and Ag, 0.1 at.% Be) on the recovery processes in Cu has been investigated. The total energy released between − 195°C and room temperature is not different from that in pure Cu within the accuracy of the measurements. The main effects of the Au and Ag solute atoms are: 1. (a) the release of energy is shifted to higher temperatures. 2. (b) the stage II fine structure is gradually vanishing with increasing solute concentration 3. (c) the recovery peak II ∗, which is weakly present in pure Cu, increases 4. (d) some new recovery peaks in the temperature range of stage III are observed. No influence was observed of 0.1 at.% Be in Cu The recovery processes in stages II and III are discussed in terms of di-interstitials and interaction of interstitials with impurities and dislocations.