J. Phys. IV France 05 (1995) C2-105-C2-109
Magnetic Aspects of Martensitic Transformations in FeNi AlloysM. Acet, T. Schneider and E.F. Wassermann
Tieftemperaturphysik, Gerhard-Mercator-Universität, 47048 Duisburg, Germany
Fe100-xNix alloys for x<34 at% ie., up to the structurally stable Invar concentration, undergo a martensitic transformation. In the parent fcc-phase these alloys show a volume enhancement which is known as the anti-Invar effect. This effect disappears at a concentration at which the martensitic transformation also no longer takes place. In a narrow concentration range of about 30≤x≤34 at% Invar, anti-Invar and the martensitic transformation can be observed simultaneously. The Invar and the anti-Invar effects are understood to be due to the instability of the magnetic moment with respect to a volume change, i.e. the moment-volume instability. Using thermal expansion measurements on Fe100-xNix, with 0≤x≤34 at%, we determine critical volumes of the γ-phase at the martensitic transformations. Furthermore we show the existence of Invar behavior in the rest Austenite in Fe70Ni30.
© EDP Sciences 1995