Influence of temperature, strain rate and thermal aging on the structure/property behavior of uranium 6 wt% Nb

Abstract
A rigorous experimentation and validation program is being undertaken to create constitutive models that elucidate the fundamental mechanisms controlling plasticity in uranium-6 wt.% niobium alloys (U-6Nb). These models should accurately predict high-strain-rate large-strain plasticity, damage evolution and failure. The goal is a physically-based constitutive model that captures 1) an understanding of how strain rate, temperature, and aging affects the mechanical response of a material, and 2) an understanding of the operative deformation mechanisms. The stress-strain response of U-6Nb has been studied as a function of temperature, strain-rate, and thermal aging. U-6Nb specimens in a solution-treated and quenched condition (ST/Q) and after subsequent aging at 473K for 2 hours were studied. The constitutive behavior was evaluated over the range of strain rates from quasi-static (0.001 sec ^{- 1}) to dynamic (2000 sec ^{- 1}) and temperatures ranging from 77 to 773K. The yield stress of U-6Nb was exhibited pronounced temperature sensitivity. The strain hardening rate is seen to be less sensitive to strain rate and temperature beyond plastic strains of 0.10. The yield strength of the aged material is less significantly affected by temperature and the work hardening rate shows adiabatic heating at lower strain rates (1/s).