The Influence of Dislocation Arrangements in Austenite on the Course of Diffusionless Transformation in Cu-Based Shape Memory Alloys

摘要

The transformation behaviour of shape memory alloys is influenced by lattice defects. Due to these defects the characteristic temperatures and mode of transformation can be varied. To examine the effect of dislocations on the transformation behaviour, CuZnAl and CuAINi alloys were deformed plastically by different amounts in the stable austenitic and in the martensitic state. The induced dislocations can be arranged as random dislocation forests, dislocation groupings, subgrain boundaries, tangles and cell walls. LM and TEM investigations connected with DSC measurements were conducted to characterize changes in microstructure and functional properties. A critical amount of plastic deformation promotes a premartensitic solid-solid state reaction even in Cu-based SMA and retards or inhibits the martensitic transformation.