The codeformation of Cu-Ag or Cu-Nb composite wires used for high field magnets has a number of important microstructural consequences, including the production of very fine scale structures, the development of very high internal surface area to volume ratios during the drawing and the storage of defects at interphase interfaces. In addition, the fabrication and codeformation of phases which differ in crystal structure, thermal expansion, elastic modulus and lattice parameter lead to the development of short wavelength internal stresses. These internal stresses are measured by neutron diffraction and transmission electron microscopy as a function of the imposed drawing strain. The internal stresses lead to important changes in elastic plastic response which can be related to both magnet design and service life and these aspects will be described in detail.
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