Recovery of Electrical Resistivity of Pure Iron Deformed at the Liquid Nitrogen Temperature

Abstract

The motion of defects in hydrogen-treated Johnson-Matthey pure iron strained at −196°C has been studied in the temperature range between −120° and 260°C using electrical resistivity measurement. There appears to be five stages of recovery; the second and the third ones centred at −130°C and −60°C, with activation energies of 0.3 and 0.5 eV, and attributed to the motion of di-interstitials and of divacancies, respectively. The time law of the decay of the above-mentioned point defects are best interpreted in terms of the attraction model by the parallel dislocation group. The stage V recovery occurs above 80°C with a continuously increasing activation energy from 0.9 to 1.8 eV in the temperature range studied (80∼260°C). This stage is attributed to the recovery of dislocations, depending on the internal stress. Defect resistivities at −196°C are estimated as follows: ρp=24×10−6 Ωcm/at %, for point defects, and ρd=8×10−19 Ωcm/cm−2 for dislocations.