The twinning orientation relationship between A and B martensite variants in a Cu-Zn-Al shape memory alloy

In the Cu-Zn-Al shape memory alloy, the variants of thermoelastic martensites which are transformed from parent phase appear as a collection of the plate groups, each consisting of three fundamental combinations A:B, A:C and A:D type pairs. All of these combinations involve a twin orientation. Understanding the twinning orientation relationships between each pair is vital to further understanding of mechanism of self-accommodation between martensite plate variants and shape memory behavior. Direct evidence is given showing that A and B martensite variants are not related by a rotation of π about [10̄91]β′(1).