US2692823A - Uranium-nickel metal alloy - Google Patents

Description

M. E. CIESLICKI ET AL URANIUM Oct. 26, 1954 -NICKEL METAL ALLOY Filed Aug. 7, 1947 INVENToRs: J/e

Patented Oct. 26, 1954 URANIUM-NICKEL METAL ALLOY Marion E. Cieslicki, Mount Lebanon,

J'. Nelson, New Kensington, the United States of America and Benny Pa., assignors to as represented by the United States Atomic Energy Commission Application August 7, 1947, Serial No. 766,940

1 Claim. ll The present invention is concerned with uranium-base alloys and more particularly binary uranium-base alloys containing nickel.

An object of the present invention is to improve the corrosion resistance of uranium and uranium-base alloys.

Another object of this invention is to produce binary uranium-nickel alloys which are useful in the design and construction of neutronic reactors.

Still another object of this invention is directed toward the formation of new and novel uranium-nickel alloy compositions which are useful as additives in the formation of other metal alloys containing uranium and. nickel.

Other objects of the present invention will be apparent from the following description taken in connection with the accompanying drawing, in which the single gure is a phase equilibrium diagram dening the uranium-nickel system.

In accordance with the present invention it has been found that the corrosion resistance of uranium and uranium-rich alloys may be substantially improved by the incorporation of a quantity of nickel in such uranium or uraniumbase alloys. The amount of nickel which may be added to uranium metal is capable of variation extending through the phase diagram wherein four distinct intermetallic compounds have been identied. The formulae, UeNi, UNi, UNiz, and UNi5 have been assigned to these compounds on the basis of thermal, X-ray and microscopic evidence. y

In order to determine the possible compositions and usefulness of uranium-nickel alloys, the constitutional diagram of the system has been determined. In examining the microstructures of ascast uranium-nickel alloys, the effects of heat treatment upon the microstructures of the varying compositions were also observed.

The initial structure of a 1.1 atomic per cent nickel alloy of uranium in the as-cast structure consists of a eutectoid matrix with precipitated or peritectic compounds at the grain boundaries. Upon heating the as-cast structure to 705 C., the microstructure appears to spherodize the eutectic and the grain boundary composition to give a fairly uniform dispersion of UsNi particles in the uranium matrix. This alloy appears to be close to the eutectoid composition. The microstructures of these as-cast 2.6, 5.4, and 10.0 atomic per cent alloys of uranium-nickel showed primary gamma uranium solid solution in a network of peritectic compound, UsNi. The atomic per cent nickel alloy of uranium con- (Cl. 'l5-134) tainedA considerable eutectic as a result of theA incomplete peritectic reaction. All these alloys responded to heat treatment. The eutectic structure in the primary phase was not evident in the alloys which were water-quenched from 715 C. It appears that the peritectic reaction had gone to completion. There appeared to be no evidence of retained beta phase in these alloys and the thermal analysis showed a break at 754 C.

The microstructure of a 15.3 atomic per cent nickel alloy was cast and examined. It was found that slightly above the peritectic compound composition, the compound of simplest atomic ratio having a composition slightly less than 15.3 atomic per cent would be UsNi at 14.3 atomic per cent nickel. X-ray diffraction patterns of the 15.3 atomic per cent nickel alloys indicate that the compound UeNi has a face centered cubic lattice with a0=4.88

Upon increasing the atomic percentage of nickel in a nickel-uranium composition, it was found that upon examining the microstructure between a 30.5 atomic per cent nickel cast alloy and 41.7 atomic per cent nickel cast alloy, there was exhibited a primary phase eutectic, but the primary phase of the 30-.5 per cent nickel alloy appeared to be different than in the 41.7 atomic per cent nickel alloy. It was found that a eutec tic alloy containing 37.4 per cent nickel contained no primary phase and appeared to be entirely eutectic. Thermal analysis fixed the eutectic temperature of the rst eutectic of nickel-uranium alloy at 738 C.

As described above, the 41.7 atomic per cent nickel alloy showed a primary phase different from uranium, and thermal analysis ofalloys in the composition range of 45-66 atomic per cent nickel showed a break at 810 C. The microstructure of the 53 atomic per cent nickel alloy =was characterized by an incomplete peritectic reaction; and upon heat treatment, the peritectic reaction went to completion. It was found that these alloys in this composition range were extremely diflicult to produce and were subject to considerable segregation. 1n examining the phase diagram, it shall be noted that a peritectic reaction occurs at 810 C. in this composition range and that the microstructure analysis indicated that the peritectic compound formed was UNi.

A third peritectic compound UNZ was formed in alloys containing from about 67 to 80 atomic per cent nickel. Thermal arrests were obtained at 985 C. indicating the peritectic compound to atomic per cent nickel showt:`

tic and was well beyond thecopoindlc'pos tion. Thus the simplest compoundiformulawhich was consistent with these data was UNis at n y atomic per cent nickel. I 1t was found th`ait"Ul\T15uw melted at 1295 C. and was identified by a hexagonal'latticef-with ao=4i'7-OJ; adco'lM f1: iflhermalarrsts Yat' lllOfl" thevthermalfanalysishigh nickelv conte1'1'tura`` niumxalfl i i pei.- centfnickelf" 'lloysi-freveal'ed afieutectic'struc# ture pluslprimarym'ickel 'fIhefmicrostructire of the 9.0 atomictpercent nickel allo'yl showed4 the same atomic structure plusa primary phaselivhich may'befieitherfnickel orriUNitzf ff" I 'Hf These new uranium-nickel alloys may be conveniently Lpreparef'lr-by melting? 'li-n vacuo lfthe' required," amountsvfo'f .uraniumy andV nickel ii'n fa refractoryrcrucible',1 suchias be 1l' 'in oxtle linedAlundurnthirnble. `f-flMicroscc'pic'iexaminations VWere mad 'onthes'e alloys? iri the i aslc'ast conditions and some n were reeexaminedaiterfappropriate heat treatment; The specimens ffwere'polishedffmechanically Ivvithf aluminaandthen el'e'ctrolytically polished with a phosphoricacid-ethylenefglycoleth lil-alcohol solution-wf: y; ,fit .-1- The alloy of.. he;presentfinventionzare useful as. protective zc oatingsfpfor.:uraniumshapes which may be `"exposed to Ilv:corr-o sive;l actionf' of f :chemical reagents fThese furaniumrnickeltalloys mayfbe cast tinto pvarious @shapes nandfformsato i betused he: constructiongiofy rjneutrionic `frea'ctorsge and lhezaddition'fof nickeltozthefuraniummetalfde# creasesgftheHatesrof ;corr o'siorr.;by -Lclzier'nic'al-y rea# gent, tions, ,containing hydrogne peroxide; f. :It1 @was f oundfthat-zthe additioniofisas little? as 4 atomic per; cent Aof nickel ".to-:euraniuml metalz i' decreased the hot water corrosion rate; o'f-lur'anium: -byfa factor-cf ,approximatelystwentyl ,i It ,shall.,be-finotedflthat ath' :',inventionrisI prig `conc erned-A with :binar-yalloypcomp'o sitions Sinclar-uta# he1microstructure's" lof# 95 alto.

nium is an essential component in the construction of neutronic reactors, it is extremely important to substantially increase the corrosive resistance of uranium Without introducing a large 5 quantity of neutron absorbers other than the llOfatomic per cent nickel having a melting point f lilfCgTaorded a new and novel low melting pointalloyhaving a high percentage of ura- `iumx;{Ill/iisfeutecticralloy Was found to exhibit ,,extremely'high'resistance to oxidation; and the "t s eutectic alloy afforded a very suitable materialto be used as an alloying addcontaining alloys," such as those having a base metalgv-'as for example, vv steel, nickel, copper or 20 the like.

When the eutectic alloy is added to a ladle ,fof'moltemsteehnickelz or ,fcoppennit sinks rapidly andiV alloysgwith the bath-'without cexce'sfv sive oxidationndlosst-oi lthe nium. ;metal.-;- rthermoraq the f eutecticcompo- 3Q nickel alloys with or without the addition-@of @the elemental-constitute a, new andinovelseries 051011:v f-,resistant;zmateriels i:

of uraniummetale: d .nu tgiWil-lfbe;understood hatl he :partie va- `alloy co positions::described above f;- ishciuldi,A not-..2I be f Ihat isfgclairnedgis AQperitecticcomposition of :matter consisting 41,5 essentially of uranium andi nickel vrepresented-.by

the-f rmula;Y UeNi ,having faceacenteredflattice

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