Фазовая диаграмма системы Pu-U

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Pu-U (Plutonium-Uranium) D.E. Peterson and E.M. Foltyn The assessed Pu-U phase diagram is based primarily on the work of [59Ell]. The maximum solubilities of U in Pu allotropes are (aPu),<0.2 at.% U; (bPu), 2 at.% U; (gPu), 0.7 at.% U; and (dPu), 0.3 at.% U [59Ell]. [61Ell] determined the maximum solubility of U in (d›Pu) to be 1.5 at.% U. [63Par] found that the addition of Pu to U lowers the allotropic transformation temperature, thus confirming the extent of the (aU) and (bU) regions determined by [59Ell]. A minimum in the liquidus-solidus curves occurs at 12 at.% U and 610 C. Pu and U form two intermediate phases: h, which exists at high temperatures, and z, which is stable at room temperature. The h phase is formed by a peritectoid reaction, (ePu,gU) + (bU) = h, at 70 at.% U and 705 C. The homogeneity range extends from the peritectoid composition to 2 at.% U and 320 C. The h phase decomposes eutectoidally, h = (bPu) + z, at about 3 at.% U and 278 C. The z phase forms by a peritectoid reaction, h + (bU) = z, at about 72 at.% U and 590 C. The z field widens toward the Pu-rich composition with decreasing temperature, reaching a maximum at 25 at.% U and 278 C and then narrowing to 31 at.% U below 278 C. [59Ell] observed that an 85 at.% U alloy quenched from the (bU) field is retained as bU at room temperature, whereas the same composition quenched from the (ePu,gU) field transforms to (aU). The h and (bPu) phases containing up to 17 at.% U can be quenched out to room temperature. The extent of (bPu) stabilization at room temperature is more pronounced for Pu-U alloys than for unalloyed Pu. 59Ell: F.H. Ellinger, R.O. Elliott, and E.M. Cramer, J. Nucl. Mater., 3, 233- 243 (1959). 61Ell: R.O. Elliott and A.C. Larson, The Metal Plutonium, A.S. Coffinberry and W.N. Miner, Ed., The University of Chicago Press, Chicago, 265-280 (1961). 63Par: H. Paruz, Comm. Energie At. Report CEA-2321 (1963) in French; TR: Argonne National Laboratory ANL-TRANS-98 (1964). Published in Bull. Alloy Phase Diagrams, 10(2), Apr 1989. Complete evaluation contains 1 figure, 5 tables, and 24 references. Special Points of the Pu-U System