Quenching Experiments with High‐Purity Iron

Iron wire of very high purity was quenched in a helium cryostat. Changes in electrical resistivity were used to measure the recovery during isochronal and isothermal annealing in the temperature range 4.2 to 1000 °K. Two sharp recovery stages were observed (first stage: 300 °K < T < 400 °K, second stage: 400 °K < T < 520 °K). The activation energy was determined by the change in slope and the Meechan‐Brinkman test (first stage: 0.48 to 0.51 eV, second stage: 1.05 to 1.1 eV). Both recovery processes follow a first‐order kinetic law. These two stages are observed after cold work as well. The first stage is attributed to the migration of carbon atoms alone and paired with vacancies, the second stage corresponds to the migration of vacancies. The recovery spectrum exhibits in three different temperature ranges a resistivity increase and a final recovery stage in the range 850 to 1000 °K. The last increase and recovery stage may be due either to the redissolution of carbon atoms or to Bloch wall motion.