Influence of oxygen concentration on mechanical properties and fracture features of V–Me (Cr,W)–Zr-system vanadium alloys at different temperatures

Abstract

A comparative study of the influence of the concentration of oxygen introduced during chemical-heat treatment and the temperature of final annealing on the mechanical properties and fracture features of low-activation vanadium alloys of the V–Me (Cr,W)–Zr system at different temperatures was carried out. It was found that the Zr-containing vanadium alloys studied in this work demonstrate an increase in the values of the yield strength with an increase in the concentration of introduced oxygen, while the maximum level of strength properties is achieved near the stoichiometric ratio СO/СZr = 2. In all cases, an acceptable level of ductility of the studied alloys is observed. The study of the thermal stability of the structural-phase state and mechanical properties of alloys was carried out depending on the chemical-heat treatment regimes. It was found that the activation of the processes of coagulation and phase transformation of ZrO2 particles occurs at a temperature of 1200°С (0.67 Tmelt). It is shown that an increase in the strength values at elevated temperatures of tension is provided by dispersion strengthening according to the Orowan mechanism, for the effective implementation of which it is sufficient to transform only a part of the ZrO2 particles into the nanosized state. The influence of the oxygen concentration on the fracture features of the studied alloys at different tensile temperatures is revealed. It was found that by effectively fixing the grain boundaries, fine ZrO2 particles contribute to the embrittlement of V–Cr–W–Zr alloy even at high tensile temperatures.