An investigation of superplasticity in a thermomechanically processed U-2Mo (α + δ) alloy

Abstract

A uranium-2 molybdenum (U-2Mo) alloy was shown to exhibit superplastic behavior over the [beta] + [gamma] two-phase field temperature regime and over a limited temperature span in the [alpha] + [gamma] field. At Oak Ridge, two distinct processes were developed that evolved microstructures conducive to superplasticity. These microstructures were shown to exhibit superplasticity (elongations [gt]500 pct) over a broad range of strain rates, from 2.5 x 10[sup [minus]4] to 1 x 10[sup [minus]2] s[sup [minus]1]. A maximum value of 700 pct elongation was reached at 695 C and a true constant strain rate of 2.5 x 10[sup [minus]3] s[sup [minus]1]. This study details the processing sequences, microstructures, strain-rate sensitivity, and maximum elongation data generated to characterize the superplastic U-2Mo alloy. In addition, the fracture and cavitation analyses conducted on constant strain-rate tensile test specimens are discussed.