G. Eggeler, Ruhr-University Bochum, Bochum, Germany; M. J. Mills, The Ohio State University, Columbus, OH
Shape memory researchers have always been more interested in crystallography, in martensite variants
and in phase transition temperatures than in dislocations. But dislocations are important in three respects.
They are created during thermo mechanical processing of NiTi shape memory alloys to adjust certain
properties (like tube or wire drawing followed by annealing). They are introduced when a SMA
undergoes training for the two way effect. And they play a role during the martensitic
transformation itself where they accomodate internal stresses (lattice invariant accomodation).
The present contribution to SMST 2009 starts with an overview on these three different areas
of overlap between dislocation plasticity and shape memory behavior. It then focuses on how
dislocations multiply during the martensitic transformation in NiTi alloys. And it finally
outlines what effects dislocations can have on functional fatigue of shape memory alloys.
Areas in need of further work are highlighted.
Summary: Shape memory researchers have always been more interested in crystallography, in martensite variants and in phase transition temperatures than in dislocations. But dislocations are important in three respects. They are created during thermo mechanical processing of NiTi shape memory alloys to adjust certain properties (like tube or wire drawing followed by annealing). They are introduced when a SMA undergoes training for the two way effect. And they play a role during the martensitic transformation itself where they accomodate internal stresses (lattice invariant accomodation). The present contribution to SMST 2009 starts with an overview on these three different areas of overlap between dislocation plasticity and shape memory behavior. It then focuses on how dislocations multiply during the martensitic transformation in NiTi alloys. And it finally outlines what effects dislocations can have on functional fatigue of shape memory alloys. Areas in need of further work are highlighted.
