Surface morphological study of the transformation strain of martensites and bainites in copper alloys

Transformation strain associated with martensites and bainites has been determined by surface relief measurements with an atomic force microscope. To this end, morphological data of transformation products have been combined with data on their crystallographic orientations, which have been determined by the electron back-scatter diffraction technique. The results have shown that the transformation strain of bainites has a comparable value to that of martensites in the same alloy. The orientation relationship between the transformation products and the parent crystal has also been determined. The relationship for bainites as well as martensites was consistent with the prediction of the phenomenological theory for the transformation. It was concluded that the transformation mechanism of bainites involves lattice shearing in a manner similar to that of the martensitic transformation. (orig.)