Abstract
Strips of 99.95 at.% Mo polycrystals annealed at 700 °C as well as the ones annealed and then aged for 6 months at room temperature were deformed in tension at various strain-rates in the range 2.1 × 10−4 to 4.2 × 10−3 s−1 till fracture. It is found that natural aging of the annealed specimens for 6 months leads to 20-30% reduction in the yield stress (YS), 18-22% reduction in the ultimate tensile strength (UTS), and 72-76% reduction in the ductility, i.e. the tensile strain emax corresponding to UTS, depending on the value of \( \dot{\upvarepsilon } \) in the tensile strain-rate range referred to. Data analysis in terms of the kink-pair nucleation model of flow stress shows that the reduction in YS of the aged Mo specimens is a consequence of lowering of the Peierls energy per interatomic spacing along the length of screw-dislocation segments trapped in the Peierls valleys on the migration of point defects to the dislocation cores during the course of natural aging. The reduction in UTS and emax is attributed to the variation in the relative contribution of the processes of dislocation multiplication and annihilation together with the reduction in the Peierls stress of the metal.
Published Version
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