Texture Optimization in the Microstructure of Mg AZ31 Alloy to Encourage Twin Formation

Abstract

The microstructure of materials is often described by its texture which is the orientation distribution (ODF) of the individual grains. The nature of this distribution governs the properties of the grain boundary characteristics. These grain boundary characteristics are known to drive the various deformation modes within the microstructure. For Mg3AlZn, the prevalent deformation mode is the formation of twins. It has been found that certain grain boundary misorientation angles are favorable for twin creation. This project seeks to utilize optimization methods to maximise the grain boundary misorientation distribution (GBMD) that encourages twin formation for an initial texture. The arrangement of these unit cells will be governed by the ODF given and the GBMD will be obtained from the spread of misorientation between them. The optimization problem will then be stated as having an objective function of maximising the appropriate GBMD for a given texture that encourages twin creation by allowing the texture to be changed, limited to certain orientations. Further constraints, such as ensuring that necessary planes of unit cells always intersect so there are no voids formed in the optimized microstructure, will be developed and applied as necessary. A method for finding optimum texture for a given grain boundary characteristic is explained. A microstructure is optimized for misorientation spread that promotes twinning.