Precipitation in CuCrZr Composites

Subjecting conductors to cold-deformation usually increases their hardness but decreases their conductivity. When we deformed solution-treated samples of Cu0.66at.%Cr0.05at.%Zr wires, however, we were able to increase hardness by ~100% while also increasing conductivity by 24%. We attribute this simultaneous enhancement of hardness and conductivity to the formation of disc-shaped, semi-coherent precipitates, less than a nanometer in thickness, during cold deformation. The driving force for this deformation-induced coherent precipitation was the presence in the matrix of 78% of total alloying elements in supersaturated solid solution. (During solution-treatment, the remaining 22% formed irregular micron-scale particles, mostly scattered distributed, that contributed only marginally to hardness.) The post- deformation aging of our samples further increased their hardness by 27%~38% and their conductivity by as much as 80%, despite the fact that the total Cr content in aging-induced coherent precipitates was only ~0.33 at.% (0.24 wt.%). These precipitates were only a couple of nanometers in thickness, but their Cr content (1.2-8.4 at.%) was relatively greater than that of deformation-induced precipitates