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SYMT: Martensitic Transformations and Shape Memory Effect

SYMT 1: Basics

SYMT 1.5: Hauptvortrag

Mittwoch, 29. März 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.