Correlation between microstructure and transformation behaviour in bulk and rapidly solidified shape memory alloys

The martensitic transformation is a structural phase transformation associa ted with a shape change of the unit cell. Although this shape change is min imized for thermoelastic martensitic transformation, it has to be accommoda ted by the surrounding material. As a consequence, the transformation chara cteristics strongly depend on the microstructure of the material. Designing the properties and characteristics of Shape Memory Alloys, requires a cont rol of its microstructure during processing. Different processing methods l eading to different characteristics of SMAs are examined in this investigat ion. in particular, the origin of the multiple martensitic transformation i s discussed in terms of dislocation cells or coherent precipitate distribut ion present according to the processing of the material.