The effect of grain boundaries on plastic deformation of TiAl

Abstract
The phenomena involving the grain boundaries of two types are discussed for polysynthetically twinned TiAl. The interfaces separating parallel lamellae are special twist boundaries and their influence on plastic deformation is treated on the mesoscopic level. The boundaries between differently oriented lamellae colonies are grain boundaries in a common sense. Their effect on plastic deformation is studied in a model for calculation of compatibility stresses in elastic continuum. Deformation behaviour is examined for crystals composed of parallel lamellae prepared by directional solidification in the <101> direction (so called Al orientation). A chosen bicrystal has the grain boundary parallel to the growth axis and the misorientation of 90°. The effects caused by the stress redistribution and those derived from the properties of crystal defects are compared.