Study of the retention of metastable phases in quenched uranium--niobium--zirconium ternary alloys

A metastable or transitional phase diagram for the uranium-rich section of the U--Nb--Zr ternary system was proposed for alloys quenched from 8500C. A review of those alloys having a bcc and a displaced bcc structure revealed a linear relation between the bcc lattice parameters and alloy content, which approximately obeys Vegard's Law over the range of compositions investigated. The monoclinic angle, γ, was found to be linearly related to the Nb and Zr contents. Metallographic examination of the samples having a monoclinic structure indicated that these samples had a Widmanstatten structure. The DPH hardness of all alloys regardless of crystal structure was found to be related to the niobium and zirconium contents by the following equation: DPH = 44.9 + 0.45 Nb2 + 8.8 Zr. (25 figures) (U.S.)