Influence of prior strain history on the tensile properties and structures of high-purity copper

Abstract

Tensile tests were made at room temperature on oxygen-free high-conductivity (OFHC) copper initially as annealed, as cold-drawn different amounts, and as prestrained in creep at 110°, 250°, and 300° F. The shape of the true stress-strain curves obtained on copper cold-drawn 34-, 40-, and 70percent reduction in area indicate a strain aging effect in the specimens when subjected to stresses in the vicinity of the maximum load. This phenomenon of strain aging is usually more closely associated with alloys of the ferrous type than with a high-purity nonferrous metal. The present results show that the strength, ductility, and hardness of the copper is markedly affected by its prior strain history. The test conditions are correlated with the tensile properties, hardness, necking characteristics, formation of microcracks, and substructures.