Magnetron sputtering of austenitic stainless steel AISI 316, which has a face-centred cubic structure
(γ), leads to films exhibiting a body-centred cubic
(α) structure
or a mixture of α- and γ-phases. The microstructure of the deposited films was studied by Mössbauer
spectroscopy, x-ray diffraction and transmission electron microscopy.
With increasing deposition temperature a phase transformation from
α- to
γ-phase was observed in these films. Instantaneous recording of the electromotive force
shows that nickel content and deposition temperature are crucial factors for phase stability
and phase formation. In room temperature deposited stainless steel films, the phase
transformation after vacuum annealing can be described by the Johnson–Mehl–Avrami
kinetic model. These phase transformations in stainless steel films during annealing can be
explained with the Gibbs–Thomson effect, where the grain boundary energy raises the
Gibbs free energy.
The high prevalence of cardiovascular disease (CVD) is largely attributable to the contemporary lifestyle that is often sedentary and includes a diet high in saturated fats and sugars and low ingestion of polyunsaturated fatty acids (PUFAs), fruit, vegetables, and fiber. Experimental data from both animals and humans suggest an association between increased dietary fiber (DF) intakes and improved plasma lipid profiles, including reduced low density lipoprotein cholesterol (LDL-C) concentrations. These observations underline that the intake of DF may protect against heart disease and stroke.
The distribution of carbon and nitrogen atoms on the octahedral interstitial sites of the
face-centred-cubic austenite phase in Fe–C and Fe–N alloys, especially in austenitic
stainless steel, is still causing controversy. In this work, results of Mössbauer experiments are
presented in order to advance the understanding of this interstitial occupation. Therefore,
laser carburized and laser nitrided austenitic stainless steel was investigated by means
of x-ray diffraction and Mössbauer spectroscopy. Three subspectra in terms of
different iron sites were resolved in the Mössbauer spectra for these iron–carbon
and iron–nitrogen austenites. The isomer shifts, the quadrupole splittings and in
particular the subspectra fractions depend on the type of the introduced atom and
undergo changes when increasing the carbon or nitrogen content. This is discussed
in connection with the existing ordering models for interstitial atoms. No clear
evidence could be found for a perfect random occupation, nor for a perfect ordered
occupation of the interstitials. Nevertheless, there seems to a tendency for a weak
attractive interaction for nitrogen interstitials, and for a stronger repulsive force
for the carbon interstitials in laser nitrided/carburized austenitic stainless steel.
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