CORROSION OF REFRACTORY METALS BY LITHIUM

Technical Report · Sun Mar 01 00:00:00 EST 1964

DOI:https://doi.org/10.2172/4085481· OSTI ID:4085481

DiStefano, J. R.

ABS>The pure metals niobium, tantalum, vanadium, titanium, and zirconium exhibit excellent resistance to dissolutive attack by lithium at temperatures even in excess of 800 deg C. However, the presence of small quantities of oxygen in either niobium or tantalum can cause the rapid penetration of these metals by lithium over a wide range of temperatures. Vanadium, titanium, and zirconium, on the other hand, do not show this susceptibility to lithium penetration even at oxygen concentrations in excess of 2000 parts per million. Penetration of niobium or tantalum by lithium results in the formation of a complex corrosion product in grain boundaries or along certain crystallographic planes. This reduces both the tensile strength and ductility of niobium. Oxygen was gettered from niobium, tantalum, and vanadium by lithium in all the tests. In the case of titanium and zirconium, oxygen redistribution occurred; but the direction, from solid metal to liquid metal or vice versa, depended on initial concentrations in the solid and liquid metal. At oxygen concentrations above 500 parts per million, temperature and grain size were the most significant variables affecting depth of penetration. Low temperatures and large grain size favored penetration along certain crystallographic planes while high temperature and small grain size favored grain-boundary attack. In tests with single crystals, penetration was observed to decrease with increased temperature. This was shown to be related to the rate at which oxygen diffused out of the niobium and was gettered by the lithium. Other variables such as time, heat treatment, prior deformation, and lithium purity were also investigated but were not found to be signiflcant in the corrosion process. Possible solutions to this problem were afforded by the addition of alloying elements to niobium. It was shown that the addition of zirconium could be effective in eliminating lithium penetration. Alloys heat treated such that oxygen was tied up as the compound ZrO/sub 2/ did not corrode. Vanadium, on the other hand, was not effective in providing corrosion protection, presumably because it does not preferentially tie up oxygen present in the alloy. (auth)

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• DOE Contract Number: W-7405-ENG-26
• NSA Number: NSA-18-014409
• OSTI ID: 4085481
• Report Number(s): ORNL-3551
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-64
• Country of Publication: United States
• Language: English

Related Subjects

METALS, CERAMICS, AND OTHER MATERIALS
ADDITIVES
ADSORPTION
COMPLEXES
CONFIGURATION
CORROSION
CORROSION PROTECTION
CRYSTALS
DEFORMATION
DIFFUSION
DISTRIBUTION
DUCTILITY
GRAIN BOUNDARIES
GRAIN SIZE
HEAT TREATMENTS
HIGH TEMPERATURE
IMPURITIES
LATTICES
LIQUID METALS
LITHIUM
MATERIALS TESTING
MONOCRYSTALS
NIOBIUM
OXYGEN
REFRACTORIES
SOLIDS
STABILITY
TANTALUM
TEMPERATURE
TENSILE PROPERTIES
TITANIUM
VANADIUM
ZIRCONIUM
ZIRCONIUM OXIDES