Study of variable elongations in the uranium-0.75 weight percent titanium alloy

Tensile specimens cut from the same gamma-quenched-and-aged, 32-mm-thick plate of U-0.75 wt percent Ti (U-0.75 Ti) alloy exhibited elongations that varied between 9.4 and 17.2 percent. Results of microhardness, electron microprobe, chemical analysis, scanning electron microscopy, transmission electron microscopy, ion microprobe analysis, optical microscopy, heat-transfer calculations, and quenching-rate studies led to the conclusion that the variable ductilities were caused by quenching rates from the gamma phase that were too slow and were different across the thickness of the plate. Work of others is cited to support this conclusion. Their work showed that quenching rates of 8 to 500C/s produced a duplex microstructure of α' and α + U2Ti phases in the U-0.75 Ti alloy, with ductilities between 7 and 26 percent, respectively. Two solutions to the problem are suggested: (1) add a third element to the alloy to slowdown the γ → α + U2Ti transformation so that titanium is retained in solution in the martensitic α'phase, or (2) substantially improve the heat-transfer coefficients in the quenching bath. The latter suggestion is the near-term solution, whereas the former suggestion is the long-range and better solution