Estimation of Local Plastic Deformation of Polycrystalline Materials

Abstract

Final properties of formed steel or another alloy pieces are affected even by plastic deformation of material. Therefore it is needful to know detail structure changes of material under conditions of plastic deformation caused by forming, grinding, drilling etc. Estimation of the deformation based on its observable macroscopic effects doesn’t correspond fully with microscopic structural changes in whole volume of deformed parts and such estimation is quite impossible in case if only surface layers are deformed. It is possible to obtain value of strain by measurement of grain boundary deformation. Effect of grains boundaries self-orientation caused by grains deformation can be identified on metallographic cut. Stereological measurement of degree of grain boundary orientation is relatively simple if axes of orientation are known (as it is in most of deformation processes). Preferred direction of grains boundaries orientation is the same as direction of deformation; however orientation is not the same thing as deformation. Therefore model of conversion of degree of grain boundary orientation to deformation based on an idealized shape of grains has been proposed. This conversion model is independent on an initial grain size – strain depends only on the shape of the grain and does not depend on its dimension. It allows experimental estimation of local plastic deformation by means of measurement of grain boundary orientation in various areas of plastically deformed parts.