Martensites, anisotropy and meso-scale interfaces in pseudoelastic NiTi shape memory alloys

10:00 AM - 11:00 AM
Martin F.-X. Wagner, Ph.D., Chemnitz University of Technology, Chemnitz, Germany
Materials Science & Technology Division
Building 4515, Conf Room 265

Email: Dr. Amit Shyam

This talk highlights some recent theoretical and experimental results on different types of interfaces in pseudoelastic NiTi shape memory alloys. It is first discussed how ab initio methods can be used to study the elastic anisotropy of an individual B19’ NiTi martensite variant. Then, the effect of twin boundaries and the generation of elastic compatibility stresses in finely twinned, martensitic microstructures is studied in a simple micro-mechanical framework. These basic results are also discussed in the light of nanoindentation results obtained from indenting single austenite grains, where the interaction of stress-induced martensitic transformation and plastic deformation by dislocation slip needs to be analyzed taking elastic anisotropy into account. Finally, on a more macroscopic scale, a localized mode of pseudoelastic deformation (formation of martensite bands under uniaxial loading) is discussed based on local strain field measurements and complementary Finite Element analysis, providing a detailed analysis of strains, phase fractions and stresses in the transition regions between fully austenitic and fully martensitic bands.

Additional Information

Dr. Wagner is Chair of Materials Engineering in the Institute of Materials Science & Engineering.


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