The interplay between deformation mechanisms in austenitic 304 steel during uniaxial and equibiaxial loading

The preferred deformation mechanisms with respect to the load path are studied in a medium stacking fault energy 304 austenitic stainless steel that exhibits both transformation induced plasticity and twinning induced plasticity. In situ neutron diffraction and post-mortem EBSD show that the transformation from gamma-austenite to alpha'-martensite is facilitated by equibiaxial loading rather than uniaxial loading. The results are discussed with respect to the evolving crystallographic texture, the presence of deformation twins and martensite under the different load paths. The evolving crystallographic texture under uniaxial loading favors the deformation twinning and delays the martensitic transformation. In contrast, under equibiaxial loading the strain is accommodated by slip along multiple slip planes, which provide nucleation sites for martensitic transformation. It is found that the preferred deformation mechanism is not only an inherent property related to the stacking fault energy, but it also greatly depends on the load path and the deformation texture.