Effects of hydrogen and temperature on fatigue of vanadium. Annual report

Fatigue behavior of vanadium unalloyed and alloyed with 132, 400, and 1000 ppM hydrogen were determined in both stress control and strain control at room temperature. In addition, stress-control tests were conducted on vanadium and the 1000 ppM H2 alloy at 400 and 6000C in air. S-N data from stress-controlled tests revealed a pronounced improvement in fatigue life for hydrided vanadium, but little or no effect for 132 ppM H2 in solution. Similarly, strain-control tests showed no effects of hydrogen in solution on either cyclic hardening or fatigue life, in marked contrast to previous results for vanadium containing hydride particles. High-cycle fatigue tests on vanadium and the V-1000 ppM H2 alloy at room temperature as a function of test frequency showed a marked decrease in life for decreasing frequency for the alloy, but little effect for vanadium. These results furnish an explanation for previously reported anomalies between fatigue lives obtained in stress and strain control tests. Additional tests run as a function of oxygen content in low hydrogen alloys show that varying oxygen levels cannot account for observed changes in properties with hydrogen. Transmission microscopy was utilized to demonstrate differences in fatigue substructures obtained with hydrogen content. 6 figures