Berlin 2005 – wissenschaftliches Programm
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DS: Dünne Schichten
DS 5: Optische, metallische und magnetische Schichten
DS 5.5: Vortrag
Freitag, 4. März 2005, 11:45–12:00, TU HS110
Gibbs-Thomson effect in reactive magnetron-sputtered stainless steel films — •Salvatore Cusenza, Christine Borchers, and Peter Schaaf — Universität Göttingen, II. Physikalisches Institut, Friedrich-Hund Platz 1, D-37077 Göttingen, Germany
Austenitic stainless steel (SS) has a face-centered cubic (γ) structure in contrast to magnetron-sputtered 316 SS films which exhibit body-centered cubic (α) structure or a mixture of α- and γ-phases.
In this work, the effect of the local environment on the hyperfine parameters, the influence of annealing, and the effect of carburizing were studied by Mössbauer spectroscopy, X-Ray diffraction (XRD), and Transmission Electron Microscopy (TEM). Vacuum annealed films were described by the kinetic model of Johnson-Mehl-Avrami. A phase transformation from α- to γ-phase with increasing substrate temperature is observed. Nickel content and substrate temperature are found as crucial factors for phase stability formation.
For carburized SS films, Mössbauer reveals a conversion of M3 C into M7 C3 Carbides (M = Fe, Cr, Ni) with increasing substrate temperature. In a small range of methane gasflow an amorphous and soft ferromagnetic phase is observed. Corrosion tests are indicating that the formation of thin oxide films on the surface are responsible for high microhardness.
The phase transformations in SS can be explained with the Gibbs-Thomson effect, where the grain boundary energy of the grain size raises the Gibbs’ free energy.