Structural and calorimetric investigations during recrystallization of rolled copper

Abstract

Polycrystalline copper was irradiated with neutrons up to integrated doses of 6·3×10²⁰ncm⁻² (>0·1Me V), then rolled to a reduction in cross-section of 97%. Single crystals of selected orientations, doped with foreign elements, were rolled up to cross-section reductions of >99%. Some of the undoped rolled crystals were irradiated with neutrons up to integrated doses of 5×10¹⁹ ncm⁻² (>0·1Me V). The heat released during heating of the rolled samples was measured. For the case of the irradiated samples, the recrystallized grain structure, the recrystallization texture, and the migration velocity of individual grain boundaries were determined after various heat treatments. Irradiation with neutrons has the effect of accelerating the overall recrystallization process. The velocity of a given grain boundary increases with increasing neutron irradiation for unimpeded grains. The microstructure, on completion of primary recrystallization, becomes increasingly finely grained with increasing irradiation, but the texture remains unchanged. Also, the recrystallization heat remains unchanged. The effect of the foreign elements on the heat of recrystallization, and on the recrystallization temperature, can be divided into two groups according to their distribution coefficient k: (a) in which the heat of recrystallization is decreased by doping and the recrystallization temperature is increased, and (b) in which the reverse is true. Elements with k<1 belong to the first group, whereas all elements of the second group have k>1. For the case of the pure copper crystals the heat of recrystallization and the recrystallization temperature change considerably with the original orientation of the crystals. The observed results are interpreted in terms of current theoretical knowledge.