Development of high strength pure copper wires by cryogenic deformation for magnet applications

A high strength pure copper conductor was fabricated by a cryogenic drawing process at 77 K where the dynamic recovery of copper was reduced. With thi s method, drawn pure copper wire achieved a strength level of 580 MPa and a conductivity of more than 96% IACS at room temperature. This strength leve l is about 45 % higher than that obtainable by an equivalent room temperatu re deformation of copper. The material had a strength level of 680 MPa at 7 7 K and the resistivity ratio was larger than six. The interesting new basi c science concerns the understanding of both strain hardening at low temper ature, the attainment of high strength due to the stable accumulation of ve ry high densities of dislocations, the change of the work hardening rate in duced by cryogenic deformation, and the texture development in cryogenic de formation. In addition, the methodology has the potential to link the devel opment of new approaches to materials selection and production to specific design needs in a variety of magnets. The potential of cryogenic deformatio n for the development of high strength conductors of pure copper is discuss ed in this paper.