ULTRAHIGH-VACUUM CREEP BEHAVIOR OF COLUMBIUM AND TANTALUM

Icreep tests of 1000 hours and greater were conducted at 20000 and 22000 F on six commercially available refractory alloyegIt pressures of 10 8 to 10- _ to The creep behavior of three columbium allo • FS-85 (Gb + 28Ta + lOW + 1Zr), (Cb. • 10W + 1Zr + 0. 1C), and Cb-752 (Cbti- 1OW + 2. 5Zr), and three tantalum alloys, T-22•Ta +9.6W + 2.4Hf +0.01,T-lTa + 8W + 2Hf), and Ta-ý10 (90Ta + 10W) was determined at stress-to-density ratios of 2. 6x104 and 1. 3X10 inches, respectively, at 20000 and 22000 F omp rison of creep behavior on the density-compensated basis shows that the tantaluma T-222 was the most creep resistant material evaluated. A total creep strain of only 0. 1 percent resulted from testing this alloy for 5000 hours at 20000 F at a stress of 15 900 pounds per square inch; while at 22000 F and 8000 pounds per square inch, 0. 65-percent strain occurred in 5000 hours. The relative order of creep resistance, on a density-compensated basis, was the same for the materials evalu