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SYMT: Martensitic Transformations and Shape Memory Effect
SYMT 1: Basics
SYMT 1.1: Invited Talk
Wednesday, March 29, 2000, 14:00–14:20, H16
Introduction — •E.F. Wassermann — Tieftemperaturphysik, Gerhard-Mercator-Universität Duisburg, D-47048 Duisburg, Germany
We briefly define what is a martensitic phase transformation and what are the characteristic features. We then focus on metallic elements and systems, where we distinguish between those in which the high temperature austenitic phase has the more open bcc lattice structure while the martensite is close packed fcc-like (Hume-Rothery systems), and vice versa those systems, in which the austenite has fcc structure and the martensite is bcc or bct (Fe-based systems). Differences in the characteristic phonon softening of the TA1-phonons as well as electronic reasons for the occurence of fcc - bcc martensitc transitions are discussed. Finally, we present in brief a definition of the shape memory effect and give some reasoning for why and when this behavior is observed in an alloy.