STRUCTURAL INVESTIGATION OF BCC-304 STAINLESS-STEEL

A detailed structural study of b.c.c. stainless steel (SS) films prepared by ion beam sputtering of a commercial grade 304 SS is presented. The as-sputtered state is first studied using several techniques, namely transmission electron microscopy and X-ray microanalysis, secondary ion mass spectrometry, X-ray photoelectron spectroscopy, conversion electron Mossbauer spectroscopy (CEMS) while the magnetic properties are also evaluated using a vibrating sample magnetometer. The material is found to be magnetically soft with a magnetization of 0.1085 T at room temperature. The second stage of the work is devoted to the film stability as a function of temperature. A good stability is found up to about 700 K. At higher temperature, we observe the alpha (b.c.c.) --> gamma (f.c.c.) phase transformation. An interesting point of the study is an increase in Fe-57 hyperfine field after annealing for 1 h at 773 K owing to the precipitation of chromium rich carbides. An isothermal kinetic conducted using the CEMS technique has also allowed the index n in the Johnson-Mehl-Avrami semi-empirical law to be determined as n almost-equal-to 0.5.