Seven Years of Uranium Alloy Development at Weldon Spring, 1959/1966. Page: 26 of 47
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beta temperature just above the alpha-beta transformation, the limit of solu-
bility for aluminum is believed to be less than 100 ppm whereas, near the beta-
gamma transformation, the beta uranium will dissolve approximately 600 ppm
aluminum. Obviously, in a binary system quenched from a temperature low in the
beta phase, much of the aluminum might have existed as UAla prior to the quench
and in all probability the particles would be:much too-coarse for
effective grain size control in any subsequent heat treatment.
The electron microprobe positively identified the uranium compounds in the
binary system as U3Si, UeFe, and UAl2, respectively. The compounds in these
binary systems were viewed as being stoichiometric since the additional trace
elements which undoubtedly existed in the compounds as substitutional impurities
were of a very low order of magnitude compared to the additive element in each
phase system. In most circumstances, each inter-metallic compound possessed a
characteristic shape and appearance and could be recognized by inspection once
the basic analysis had been performed. In the uranium-silicon system, however,
the peritectoid reaction between gamma uranium and U3Si2 below 9250C. to produce
gamma uranium plus U3Si offered the complication that the U3Si precipitate had
much the same appearance as the original U3Si2. In this circumstance, a specific
microprobe analysis was necessary to distinguish between the two compounds.
Ternary Alloy Systems
Aside from laying the groundwork for knowledge of the quaternary system, the
interest in exploring the ternary diagrams was two-fold. It was desirable to
learn on the one hand whether, with a three-element system, different and
additional compounds might exist and, on the other whether the binary compounds
which had been recognized in the two-element system would be appreciably altered
in composition or characteristics by the presence of a third element.
The work to datel4pl8,,2O,2,27,36, 5,57,5a,64 has discovered no new compounds
other than slight variations in those identified in the binary alloys due to
solubility of a third element. The three compounds U6Fe, U3Si, and UAl2 show
different solubilities for a third element in the sense that, with some
combinations, there has been almost no detectable additions In the remaining
cases, the limit of solubility has been modest but, nevertheless, easily
measured. In UeFe, for instance, aluminum has scarcely been detected, whereas
silicon has been found up to a level of approximately 0.5 weight percent. It
is interesting to note, in this case, that with the presence of silicon, the
iron level has been reduced to a corresponding degree, and calculated weight
percentages from a formula of U6oFe7Si3 match the analytical data remarkably
In a similar vein, U3Si will dissolve a modest quantity of aluminum (approxi-
mately 0.3 weight percent) but shows essentially no solubility for iron. Finally,
UAl2 will accept only an extremely low amount of silicon in a ternary alloy but
does dissolve iron up to a level of perhaps 2.25 weight percent. Here again,
the level of aluminum appears to have been reduced by the addition of the iron.
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Fellows, J. A. Seven Years of Uranium Alloy Development at Weldon Spring, 1959/1966., report, January 1, 1966; Weldon Spring, Missouri. (https://digital.library.unt.edu/ark:/67531/metadc1033773/m1/26/: accessed March 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.