Microstructures and Mechanical Properties of Steels and Alloys Subjected to Large-Strain Cold-to-Warm Deformation

Abstract

The effect of large-strain cold-to-warm deformation on the microstructures and mechanical properties of various steels and alloys is critically reviewed. The review is mainly focused on the microstructure evolution, whereas the deformation textures are cursorily considered without detailed examination. The deformation microstructures are considered in a wide strain range, from early straining to severe deformations. Such an approach offers a clearer view of how the deformation mechanisms affect the structural changes leading to the final microstructures evolved in large strains. The general regularities of microstructure evolution are shown for different deformation methods, including conventional rolling/swaging and special techniques, such as equal channel angular pressing or torsion under high pressure. The microstructural changes during deformations under different processing conditions are considered as functions of total strain. Then, some important mutual relationships between the microstructural parameters, e.g., grain size vs. dislocation density, are revealed and discussed. Particular attention is paid to the mechanisms of microstructure evolution that are responsible for the grain refinement. The development of an ultrafine-grained microstructure during large strain deformation is considered in terms of continuous dynamic recrystallization. The regularities of the latter are discussed in comparison with conventional (discontinuous) dynamic recrystallization and grain subdivision (fragmentation) phenomenon. The structure–property relations are quantitatively represented for the structural strengthening, taking into account various mechanisms of dislocation retardation.

Double strengthening induced by grain boundary segregation of solute elements in gradient nano Ni–Co alloys

“…During the process of strain increase, the alloy model, atomic energy, and grain morphology change. 31,32 In order to further observe the secondary strengthening mechanism of the composite structure with gradient and segregation during tensile deformation, Fig. 2(a)-(f) compare and show the structural deformation of the gradient structure and the gradient structure with segregation during deformation.…”

Effect of Friction Stir Welding and Tempering on the Microstructure and Strength of a Tempformed Low-Alloy Steel

“…The microstructures evolved in the tempformed steel were affected by a large strain warm rolling. The grain boundary misorientation distributions developed during large strain deformation are commonly characterized by a small peak against low-angle sub-boundaries superimposed over a flat-type distribution with almost the same fractions of various high-angle misorientations [26]. In the case of uniaxial deformation, like rolling or drawing, an increase in the total strain may be accompanied by an increase in the fraction of the high-angle boundaries with misorientations close to 60 • [27].…”

Analytical modeling of fatigue crack growth in plastically pre‐strained steels

“…During the cold-forming process, the metal is subjected to severe plastic deformation caused by slip and twinning processes at a microscopic level. 8 The dislocation network created by multiple slips and sequence of dislocation stacks at the grain boundaries prevents dislocation movement, increasing the flow stress and hardness through work hardening processes. 9 As a consequence, the mechanical properties of the metal are affected, resulting in an increase in strength and a decrease in ductility.…”