Abstract
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Martensiteplates in �����1 shape memory alloys commonly form self-accommodating groups of four plate variants with habit plane normals clustered about a {1 1 0} pole of the parent phase. In the present work, the crystallography of martensitic transformation in a Cu-Al-Ni-Mn shape memory alloy has been investigated with particular emphasis on accurate habit plane determination. The characteristically high martensite start (Ms) temperature of �����1 alloys makes it impossible to analyse samples containing isolated plates within a ��1 grain at ambient temperature. However, the parent ��1 grain orientation has been determined in this work by means of a new method of junction plane trace analysis, which is based on the knowledge that the junction planes are precisely {1 1 0}��1 planes. The mutual consistency of the experimental results indicates that this technique of junction plane traces analysis is a viable method for determining the parent ��1 grain orientation. Habit plane normals were determined by two surface trace measurements and referred to the parent crystal basis by using the ��1 grain orientation matrix. The habit plane normal was determined to be close to {1 5 5}��1 with the scatter in a series of mean value determinations being less than �� 1.2��.