Effects of cryogenic equal channel angular deformation on copper 101

Abstract

Grain size in polycrystalline metallic materials significantly influences physical and mechanical properties. At room temperature, large grain size is generally associated with low strength, hardness and ductility. Fine grained microstructures show an increase in strength due to a larger grain boundary surface area per unit volume. One way to obtain fine grained microstructures is through cold working and recrystallization of the material. In this study, oxygen-free high-conductivity copper 101 was cold worked by being subjected to severe plastic deformation (SPD) at room temperature (23 °C) and at -196 °C under liquid nitrogen. Cold working was imparted by equal channel angular deformation (ECAD). Before extrusions were performed, a special ECAD tool was designed and built, which was capable of operating under the high loads resulting from forcing a billet through the die at -196 °C. Hardness, tensile strength, electrical resistivity and annealing experiments were performed following deformation along with optical microscopy and transmission electron microscopy (TEM) to observe changes in properties and grain morphology.