Development of Precipitation Strengthened Columbium Base Alloys
Final rept. Mar 1969-Sep 1970
WESTINGHOUSE ASTRONUCLEAR LAB PITTSBURGH PA
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A columbium base alloy composition, Cb-22W-4Hf-0.05C-0.05N designated C-6, was developed which can be thermally treated to alter its strength properties. In the as-solution annealed and aged condition, the 0.2 offset yield strength is 87,000 psi at 1400F and 82,000 psi at 2200F. Although developed primarily as a forging alloy, the composition can be processed to sheet with final rolling at 600F. The C-6 composition evolved from studies of Cb-22W base alloys with zirconium and hafnium additions in combination with carbon andor nitrogen. Zirconium additions were superior to hafnium at the 2 atom percent level in enhancing response to thermal treatment however, hafnium bearing compositions were more fabricable than those containing zirconium. Partial substitution of tungsten with molybdenum showed that on an atom for atom basis, molybdenum was half as effective as tungsten with respect to improving creep resistance but was equally detrimental in raising the ductile to brittle transition temperature.
- Metallurgy and Metallography