Cold worked Cu-Fe-Cr alloys

The aim of this project was to investigate the properties of copper rich Cu -Fe-Cr alloys for the purpose of developing a new cost effective, high-stre ngth, high-conductivity copper alloy. This paper reports on the influence o f cold work. The age hardening response of the Cu-0.7%Cr-2.0%Fe alloy was m inimal, but the resistance to softening was superior to that reported for a ny commercial high-strength, high-conductivity (HSHC) copper alloy with com parable mechanical and electrical properties. For example, an excess of 85% of the original hardness of the 40% cold worked alloy is retained after ho lding at 700 degreesC for 1 hour, whereas commercial HSHC Cu-Fe-P alloys ha ve been reported to soften significantly after 1 hours exposure at less tha n 500 degreesC. The Cu-0.7Cr-2.0Fe alloy would therefore be expected to be more suitable for applications with a significant risk of exposure to eleva ted temperatures. Optical microscope examination of cold worked and aged mi crostructures confirmed the high resistance to recrystallization for Cu-0.7 %Cr-2.0%Fe. The Zener-Smith drag term, predicting the pinning effect of sec ond phase particles on dislocations in cold worked microstructures, was cal culated using the precipitate characteristics obtained from TEM, WDS and re sistivity measurements. The pinning effect of the precipitate dispersions i n the peak-aged condition was determined to be essentially equivalent for t he Cu-0.7%Cr-0.3%Fe and Cu-0.7%Cr-2.0%Fe alloys. A lower recrystallisation temperature in the Cu-0.7%Cr-0.3%Fe alloy was therefore attributed to faste r coarsening kinetics of the secondary precipitates resulting from a higher Cr concentration in the precipitates at lower iron content. (C) 2001 Kluwe r Academic Publishers.