COLUMBIUM (NIOBIUM) ALLOYS FOR STRUCTURAL APPLICATIONS.

This paper describes results of a test program in which four sheet columbium alloys have been evaluated. Tensile tests have been carried out on Cb752, FS85, SU31 and WC3015 from room temperature to 1427 degree C (2600 degree F) in a vacuum of 1. 33 - 7. 99 multiplied by 10** minus **3N/m**2 (1 minus 6 multiplied by 10** minus **5 torr). Bend transition temperature of the alloys in uncoated, coated and welded conditions also have been reported. From the overall strength and ductility standpoint, it is found that FS85 is superior for structural applications where creep rate is the principal material selection criterion, but CB752 being slightly superior to FS85 from tensile strength standpoint. The higher elevated temperature strength of SU31 is marred by its relatively high ductile-to-brittle transition temperature in welded conditions. WC3015 has been found to be unsuitable for sheet structural application.