每年出版 4 期
ISSN 打印: 2572-4258
ISSN 在线: 2572-4266
Indexed in
CALCULATION OF THE INTERGRANULAR ENERGY IN TWO-LEVEL PHYSICAL MODELS FOR DESCRIBING THERMOMECHANICAL PROCESSING OF POLYCRYSTALS WITH ACCOUNT FOR DISCONTINUOUS DYNAMIC RECRYSTALLIZATION
摘要
Many of the existing constructions and parts from metals and alloys, used in various fields of technology and industry, undergo thermomechanical processing. This allows forming a grained and defect (internal) structure of the material in order to obtain the desired physical and mechanical properties. As a consequence, simulation of evolution of the internal structure of metals during plastic treatment at different temperatures is a relevant problem. For this purpose, the most advanced is the approach based on multilevel simulation and physical theories of plasticity, which explicitly describe the mechanisms of inelastic deformation and their carriers, as well as the processes that accompany plastic deformation. This approach includes two classes of models, namely, direct and statistical models. Statistical models consider the representative macrovolume of material (macropoint) as an aggregate of individual crystallites, combined in a polycrystal by the hypothesis of equality of strains (Voigt) or stresses (Reuss). Direct models are divided into two types. The first type of models considers explicitly the grain structure of the material and is applied only to the calculation of a small number of grains of the representative volume, given the existing computational restrictions. The second type of models is "hybrid" and uses numerical methods (for instance FEM). In this case, each point of integration is assigned a finite set of crystallites and polycrystalline aggregate response is determined using a statistical model. The purpose of the work is to create a two-level statistical model to describe the inelastic deformation of the representative volume of the polycrystal in a wide range of temperatures. The developed model can be integrated into a direct model of the second type. Elevated temperatures of deformation lead to the activation of the elastic stress relaxation processes, i.e., dynamic recovery and dynamic recrystallization. The first process occurs due to reconstruction of dislocation substructures; the description of the second process requires consideration of changes in the morphology and structure of the grains and their boundaries. In the present paper we consider the approach to the description of discontinuous dynamic recrystallization, which is based on the mechanism of the movement of the initially existing polycrystal boundaries. To solve this problem the Bailey-Hirsch criterion is used. This criterion is based on comparing the difference between the energy stored in the neighboring grains and the surface energy of the boundary between them. The method for determining the grain boundary energy is the basis of the Schober-Balbuffi ratio and the modified model of coincidence site lattice. The results are compared with experimental data and allow judging about the applicability of this approach to the problem.
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