FEM Simulation of microstructure refinement during severe deformation

The majority of methods of severe plastic deformation (SPD) used for producing ultra-fine grained (UFG) and nano materials involve the non-uniform distribution of strains in the workpiece. To make the refinement of grains uniform, interlinked operations are used in which either the orientation of the workpiece or the type of SPD is changed in some sequence. Each operation has its own set of control parameters affecting the output result. As a result, the optimization of the total chain of operations becomes very difficult, especially taking into account that each stage of material processing comes from the previous one with a certain non-uniformity of the structure. To deal with such types of problems the capability of tracing the transformation of the microstructure and accounting for its effect on mechanical properties in finite element modeling (FEM) is required. There are a number of detailed physical models of grain refinement and texture formation, but very often they are too complicated for practical engineering simulations. The mechanics of SPD are also studied and simulated in many works, but normally it is assumed that material is uniform, isotropic and its properties don't change during deformation. In this paper a microstructurally-coupled FE model of the SPD process is proposed. The question of selection and verification of macroscopic and microscopic constitutive relations is discussed. The results of a simulation made in QForm are analyzed and compared with some initial experimental data.