Dimensional anisotropy during phase transformations in a chemically banded 5140 steel. Part I: experimental investigation Original Research Article

Dimensional anisotropy associated with chemical banding was investigated via quench dilatometry. The material used in this research was fabricated by roll bonding alternately stacked sheets of a standard 5140 steel and a modified 5140 with a higher manganese content. The resulting plate had a well defined manganese banding pattern with a known segregation bandwidth. Cylindrical dilatometer specimens were machined with the axial direction aligned parallel and perpendicular to the segregation planes. The banded steel was thermally cycled so that the material alternated between austenitic and martensitic structures. Results for multiple thermal cycles revealed that tensile plastic deformation occurs normal to the segregation plane and compressive plastic deformation occurs parallel to the segregation plane. An examination of the transformations associated with heating and cooling showed that an exaggerated apparent transformation strain was measured in the direction perpendicular to the segregation layers and a suppressed apparent transformation strain was measured parallel to the segregation layers.