Effects of hydrogen on some mechanical properties of vanadium-titanium alloys
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I.
INTRODUCTION
E A S E of fabrication, excellent mechanical properties over a wide temperature range, and resistance to radiation damage are properties of refractory metals and alloys which make them desirable candidates for first wall material in controlled thermonuclear reactors. A problem exists, however, due to the presence of hydrogen and its isotopes within these reactors since they can cause severe embrittlement of these metals and alloys. The present study covers solid solution V-Ti alloys up to 30 at. pct Ti. Although the mechanical properties of V-Ti alloys have been assembled and documented in a review article by Harrod and Gold,~ little work has been done on the effects of hydrogen (and its isotopes) on these properties. Tanaka and Kimura 2 have examined the effect of increasing hydrogen content in V-Ti alloys up to 3.9 at. pet Ti. They determined that in these dilute alloys there was a critical hydrogen concentration that produced embrittlement for a specific Ti content and that embrittlement could be mitigated by further addition of titanium. These same authors also have determined the solubility and diffusion of hydrogen near room temperature for V-Ti alloys up to 19 at. pet Ti. 3 The purpose of the present paper is to examine the effects of hydrogen on the mechanical properties of selected V-Ti alloys and to characterize any embrittlement found. Although specific details of the embrittlement mechanism(s) are not quite clear at the present time, it should be pointed out that a similar study on V-Nb alloys 4 yielded results which are quite compatible with the present ones. The similarity of the effect of hydrogen on the low Ti alloy compared to the results obtained on pure V is also discussed.
II.
MATERIALS AND P R O C E D U R E S
The double-electro-refined vanadium used in this investigation was obtained from the U.S. Bureau of Mines in Boulder City. 5'6 Titanium in the form of 99.96 pet pure c.v. OWEN, Associate Metallurgist, and O. BUCK, Senior Metallurgist, are with AmesLaboratory,Iowa State University,Ames, IA 50011. T.J. ROWLANDis a Professor with the Metallurgy Department, University of Illinois, Urbana, IL 61801. Manuscript submitted February 13, 1984. METALLURGICALTRANSACTIONSA
EL-60 + 16 mesh sponge was purchased from the Titanium Metal Corporation. All material needed for alloy preparation was weighed under one atmosphere of helium since the electro-refined vanadium crystallites are known to be hygroscopic. Vanadium-titanium alloys of five different compositions were weighed out in this manner and then transferred rapidly to an inert gas arc-furnace where they were consolidated into finger-shaped ingots. These alloys are listed in Table I along with the chemical analysis for the Ti, O, and N content of each alloy. The alloy ingots, and an ingot of pure vanadium, were reduced to a final diameter of 2.54 mm by a controlled sequence of swaging at room temperature followed by intermediate vacuum annealing at 1123 K. The finished rod was cut into 50.8 mm lengths and a 25.4 mm gage length,
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