Orientation relationships of martensite variants determined by electron backscatter diffraction

Abstract

Orientation relationships between the parent phase and 2H type martensite, and between different variants in a plate group of martensite in the CuAlNi shape memory alloy were determined by electron backscatter diffraction. The result reveals clearly that the basal planes of different correspondence variants of the 2H martensite originate from different {110} P planes of the parent phase, and the [0 1 0] 2H axis of each correspondence variant originates from one of the 〈001〉 P axes of the parent phase. Our result reveals also the typical relationships of four habit-variants A, B, C and D in a martensite plate group, and that the habit-variants A and C (and equivalently B and D) are twin-related by an {121} 2H mirror plane, and the habit-variants A and D (and B and C) are twin-related by an {101} 2H mirror plane. Usually, variants A and C (and B and D) form spear morphology and variants A and D (and B and C) form fork morphology.