Contamination Hardening of SU-31 and FS-85 Columbium Alloys

Abstract

A study has been made of the contamination hardening of SU-31 and FS-85 columbium alloys which results when samples are exposed in air at temperatures of 1400 to 2600 F. Diffusion coefficients for the principal contaminant, calculated from the hardening profiles, are in good agreement with data previously reported for diffusion of oxygen in pure columbium. From that agreement it has been concluded that the hardening in the alloys is principally due to the absorption and diffusion of oxygen from the air. Activation energies measured were 22.5 kcal/mol for SU-31 and 20.3 kcal/mol for FS-85. Based on the measurements of this study, SU-31 has a higher resistance to contamination hardening than FS-85 by about a factor of two.