Correlation of temperature and grain size effects in the ductile-brittle transition of molybdenum

Abstract

An experimental investigation of the effects of temperature and grain size on the tensile properties of high purity molybdenum showed that transitions from ductile to brittle behaviour occur with both decreasing temperature and increasing grain size. Based on the assumed temperature-independence of the critical stress criterion for cleavage fracture, both of these transitions were interpreted largely in terms of the plastic strain dependence of this critical fracture stress (σ_c). The grain size dependence of σ_c at constant strain was found to be of the form σ_c=σ_c ⁰ + k _c l-^1/2, in which σ_c ⁰ is strain dependent and k _c=2 × 10⁸ dyne-cm^−3/2.