A Study of Plastic Deformation Mechanisms Associated with Twin Variant Selection in Titanium

摘要

An interrupted "in situ" EBSD orientation measurement based on a split sample in channel die compression was proposed and performed in order to provide information on many issues associated with deformation twin, such as the formation and growth of twins, the interaction between variants and so on. With this method, we are able to obtain the timeresolved information on the occurrence of the twin variants, their growth, the interaction between variants and the interaction with the grain boundaries. Two different types of twinning were activated during the deformation: {10-12} tension and {11-22} compression twin. The formation and growth of these two types of twin are quite different. {1122} twin shows Multiple Variants System (MVS), which means it always exhibits three or four variants in one grain. This because the c axes of matrix are close to the compression load, thus the resolved shear stress applied on the six variants are close. In the opposite case ,{10-12} twin shows Predominant Variant System (PVS). It only exhibits one variant because the c axes of matrix are nearly perpendicular to the load, only one variant suffers very high resolved shear stress. This predominant variant thus grows fast through almost the whole matrix grain.