EBSD-Based Crystallographic Study on a Ni-Mn-Ga Alloy with Incommensurate 7M Structure
Our recent work on EBSD-based characterization of incommensurate 7M modulated martensite in a polycrystalline Ni50Mn30Ga20 alloy were summarized. The 7M martensitic plates were revealed to be self-accommodated in colonies, where each colony consisted of four types of variants that were twin related. All the pairs of variants can be categorized into three twinning modes, i.e. type-I, type-II and compound twins. The twin interface planes were in coincidence with the respective twinning planes. Using the measured orientations of adjacent martensitic variants, the orientations of parent austenite grains were calculated under the assumed orientation relationships for the austenite to martensite transformation. The energetically favorable orientation relationship between austenite and martenstie for the martensitic transformation was identified to be the Pitsch relation.
Asim Tewari, Satyam Suwas, Dinesh Srivastava, Indradev Samajdar and Arunansu Haldar
Z. B. Li et al., "EBSD-Based Crystallographic Study on a Ni-Mn-Ga Alloy with Incommensurate 7M Structure", Materials Science Forum, Vols. 702-703, pp. 530-535, 2012