Crystallography and morphology of martensite in a Cu-11.8wt% A1-4.0wt% Ni-4.0wt% Mn shape memory alloy

This thesis reports an investigation of pi ( body centred cubic ) to pi'( monoclinic ) martensitic transformation in a Cu - 1 L8wt%Al - 4.0wt%Ni - 4.0wt%Mn shape memory alloy. In Part A of this thesis, a detailed review is presented of shape memory behaviour, applications of shape memory alloys, general properties of pi to Pi' martensitic transformation, the crystallography of martensitic transformation in copper - based shape memory alloys, and the phenomenological theory of the martensitic transformation. A summary is also given of published theoretical predictions and experimental results for the crystallographic features of Pi to pi' martensitic transformation in various copper - based alloys. The experimental work is presented in Part B. The investigation included : the relative frequencies of the crystallographically different kinds of junction planes m Pi martensite; the characteristics of the pi' to pi reverse transformation; and crystallographic features of Pi to Pi' martensitic transformation including the lattice parameters, pi grain orientation, habit junction plane normals and habit plane normals. Finally, the experimental results for the habit plane and habit junction plane normals are compared with the theoretical predictions of the phenomenological theory.