Regensburg 2000 – scientific programme
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SYMT: Martensitic Transformations and Shape Memory Effect
SYMT 1: Basics
SYMT 1.5: Invited Talk
Wednesday, March 29, 2000, 15:50–16:20, H16
Surface Effects in Martensitic Transformations by X-Ray Scattering — •U. Klemradt1, G. Landmesser1, M. Aspelmeyer1, T.R. Finlayson2, J. Peisl1, and S.C. Moss3 — 1Sektion Physik und Center for Nanoscience, Ludwig-Maximilians-Universität München — 2On leave from Monash University, Clayton, Victoria 3168, Australia — 3Physics Department, University of Houston, TX, USA
Diffusionlesss transformations, despite their widespread use in functional materials, have continued to present challenges for basic research, including premonitory phenomena and the elusive nucleation process. Using recent data from Ni-Al and Ni-Mn-Ga alloys, we will show how in-situ surface x-ray scattering experiments (and the availability of synchrotron radiation) can be applied to shed new light on these issues. Surface relief has traditionally been used in evidence of martensite formation on macroscopic scales. Here we will discuss the complementary use of advanced x-ray scattering geometries to cover multiple length scales from the Ångstrom level up to mesoscopic lengths. Grazing-incidence diffraction studies of crystallographic aspects of the transformation will be discussed and compared to specular and diffuse reflectivity experiments, which probe with high sensitivity incipient changes of the surface morphology. The existence of surface precursors that are both qualitatively and quantitatively different from bulk precursor effects will be addressed.