Splat cooling of some actinide alloys

Several new metastable actinide alloys were produced by rapidly quenching small specimens from the melt. Among these are: (1) the high temperature bcc phases of Pu (epsilon-phase) and Np (γ-phase) which have been retained at room temperature by splat cooling alloys with Ti or Ga, (2) eta-Pu(Ga), an ordered cubic phase of the substoichiometric CsCl type; this phase exists under equilibrium conditions at high temperatures over the composition range from about 20 to 40 at. percent Ga; its previously unknown structure was determined from the diffraction patterns of splat-cooled alloys, (3) delta1-Pu(Ga), a tetragonal phase of the β-Np type containing 12.5 to 20 at. percent Ga and (4) a continuous series of fcc solid solutions across the solubility gap in the Pu--Ce system. Metastable delta-Pu(Ti) and delta-Pu(Ga) solid solutions were produced at 200C in alloys containing about 25 at. percent or less of Ti or Ga, and a metastable α-Np(Ga) solid solution was produced in alloys with less than 10 at. percent Ga. These new actinide alloy phases are reviewed and the anomalous increase in atomic volumes of α-Np(Ga), γ-Np(Ga) and epsilon-Pu(Ga) concentrated solid solutions with increasing Ga content is discussed. (U.S.)