Electron Backscattered Diffraction Study of epsilon /alpha Martensitic Variants Induced by Plastic Deformation in 304 Stainless Steel

摘要

The electron backscattered diffraction (EBSD) technique has been used to assess crystallographic features of the residual y phase and the strain-induced el a' martensites in a 304 stainless steel, tensile tested to 10 pet strain at T = - 60 deg C. The martensitic transformation rate varies according to the gamma-grain orientation against the applied stress and the y-grain size. The alpha-transformation textures as well as the gamma-misorientation spreads observed in specific gamma-grain orientations have been analyzed. Large misorientation spreads are observed in the less-transformed y grains. This reveals an important crystallographic slip activity, even if less strain-induced martensite has been formed. A strong gamma-- >alpha variant selection was detected in the cube- and Goss-oriented y grains for which the transformation is less developed. For the {110}<111> and copper-oriented gamma grains, the amount of a' martensite is significantly higher and the gamma-- >alpha variant selection is less pronounced. This variant selection is then analyzed on at a local scale and is related to the presence of {111 }localized deformation bands on which further epsilon/alpha martensites have nucleated.