Method and Apparatus for Making High Strength Metals with a Face Centered Cubic Structure
The invention comprises a method and apparatus for strengthening metals while limiting the dynamic recovery phenomenon and maintaining ductility. More precisely, this invention provides a process for increasing the strength of pure copper and other face-centered cubic (fcc) matrix alloys while maintaining good ductility. A material sample is first subjected to equal channel angular pressing to produce an ultra fine grain ("UFG") structure. The UFG structure is then subjected to cryogenic drawing to reduce the cross-section and increase the strain density. Finally, the sample is subjected to cryogenic rolling to reduce its thickness.
This method attains high strength through the stable accumulation of very high dislocation densities. The work hardening rate is changed by deforming the material under cryogenic conditions. The methodology can potentially be applied to many different materials which suffer dynamic recovery and consequent low strain hardening when deformed at room temperatures. The inventive method can also produce highly-aligned dislocations. If, as an example, the dislocations are aligned with the central axis of a copper wire, the dislocations will have a greatly-reduced effect on the wire's conductivity.