True Stress vs Temperature Diagram of Structural States for Polycrystalline bcc Metals

For the first time, a new type of a diagram of structural states is constructed for polycrystalline bcc metals. This true-stress-vs-temperature diagram is a regular collection of temperature dependences of critical stresses corresponding to successive changes in the type of dislocation structure from the onset of plastic deformation to fracture within the temperature range from completely brittle fracture to the formation of a new grain structure. On the basis of analysis of true-stress-vs-temperature diagrams for metals and alloys (Mo, Fe, and Fe–3%Si) with the help of the thermal activation analysis of the temperature dependences of critical stresses, we establish the regularities and distinctive features of the formation and behavior of the temperature–force boundaries and domains of existence of certain structural states and identify the mechanisms of plastic deformation within the limits of each of these domains.