Regensburg 2004 – scientific programme

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MA: Magnetismus

MA 23: Hauptvortr
äge - Symposium Magnetic Shape Memory Alloys (zusammen mit M)

MA 23.1: Invited Talk

Thursday, March 11, 2004, 10:15–10:45, H23

Martensite: Introductory Remarks — •E.F. Wassermann — Experimentalphysik,Universität Duisburg-Essen, D-47048 Duisburg,

As a general introduction to the field of magnetic shape memory alloys (MSMA), we briefly define what is a martensitic phase transformation (MPT) in general and what are the characteristic features. We then focus on the metallic elements and systems, where we distinguish between Fe-based systems, in which the austenite has fcc structure and the martensite is bcc (or bct), and the Hume-Rothery systems, in which the opposite structural behavior is observed. Typical for the latter systems is the phonon softening occurring at certain q-vectors of the Brillouin Zone at temperatures above Ms. We will briefly discuss these precursor effects and their relevance to MPTs. We will then highlight in general the shape memory behavior, the one way-, the two way- and the all round-effect, and briefly touch the present microscopic knowledge of these effects. Finally, a short overview of practical applications of SMA will be given.