High temperature deformation of austenite: Texture and anisotropy effects

The deformation of low carbon steels at high temperature in austenite is technologically important but its study is complicated by the decomposition of austenite upon cooling which does not allow for direct characterization of the microstructure. In this study, the grain size and crystallographic texture of austenite were assessed by reconstruction of the prior austenite grains from the ambient temperature bainite. The austenite microstructure was found to consist of nearly equiaxed grains with annealing twins and a texture similar to copper deformed in plane strain. This texture was rationalized by visco-plastic self-consistent (VPSC) simulations. The presence of a non-random texture was predicted to lead to an anisotropic plastic response which was confirmed by experiments. A constitutive model for the high temperature flow stress was established in the Kocks-Mecking framework for work hardening and fit to experiments. The model described the experiments well and was validated by independent compression tests. Finally, the work hardening behaviour was assessed in comparison to other FCC metals. Its behaviour was found to fall between copper and silver, closer to copper.