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A series of vacuum-anneals at temperatures from 900 to 100{degrees}C for 1 to 4 h was carried out on small heats of vanadium alloys with Cr and Ti contents ranging from 2 to 6wt. %. The alloys examined on this work were V-3Cr-3Ti, V-4Cr-4Ti, V-5Cr-5Ti, V-6Cr-3Ti, and V-6Cr-6Ti. Optical miscroscopy, TEM, and microhardness testing were conducted. Variation in Cr and Ti over the range of 3 to 6 wt% had no discernible effect on recovery/recrystallization behavior. The hardness of both recovered and recrystallized structures increased with total (CR + Ti) content. In order to study the effect of Cr and Ti content on mechanical properties, Charpy impact testing and tensile testing were carried out on small heats of compositional variants. The V-4Cr-4Ti-Si alloy, in a fully recrystallized conditions, exhibited a high level of resistance to cleavage failure with a DBTT at {approx} 190{degrees}C. The alloy containing higher concentrations of Cr and Ti, in a fully recrystallized condition, exhibited a DBTT around -100{degrees}C, whereas the V-3Cr-3Ti alloy failed by pure ductile shear at liquid nitrogen temperature without any ductile-to-brittle transition. Tensile testing was conducted on SS-3 tensile specimens punched from 0.762-mm-thick plates of V-3Cr-3Ti and V-6Cr-6Ti. The tests were done inmore » air at temperature at strain rates ranging from 10{sup -3} to 2x10{sup -1}/s. For V-6Cr-6Ti, both the 0.2% yield stress (YS) and the ultimate tensile strength (UTS) were higher than those for V-3Cr-3Ti at all strain rates. Both YS and UTS showed a similiar trend in incremental increase with strain rate for the two alloys. In the same token, both alloys exhibited an identical behavior of almost no change in uniform and total elongation up to a strain rate of 10{sup -1}/s and a decrease with further increase in strain rate.« less |
