Strain induced martensite formation in stainless steel

Abstract

The Conversion Electron and X-ray Mössbauer studies of the surface of Type 316 stainless steel at 400 K, 300 K, and 100 K show that both the substitutional and interstitial elements perturb the cubic symmetry at the iron site. The single peak of austenite is a superposition of at least five quadrupole split doublets whose magnitudes and intensities depend on the type and concentration of the impurity elements. However, when the surface of the stainless steel is plastically deformed, a layer of martensite about 5000 Å thick is formed on the austenite base. This layer consists of a mixture of 31 pct martensite with the rest being the original austenite. The magnetic environment of the iron in this martensite is controlled by the concentration of alloying elements, and the distribution of the hyperfine fields is determined by the number of nearest and next nearest neighbor impurity atoms. The magnetic field decreases linearly at first as the number of nearest neighbors increases and then follows a nonlinear trend for a number of nearest neighbors. The temperature dependence of the sublattice magnetization is different for each number of neighbors, and a Curie temperature has been estimated for each site.