SEGMENTED TWIN BOUNDARIES IN 10M MODULATED Ni-Mn-Ga MARTENSITE

摘要

Different configurations of type I and type II twin boundaries in five-layered modulated(10M)Ni-Mn-Ga martensite were analyzed by electron backscatter diffraction in the scanning electron microscope. Based on precise monoclinic structure data direct experimental identification of all possible variants in 10M martensite was possible revealing a complex microstructure of 10M martensite. Beside type I and type Ⅱ twin boundaries {100)compound twin boundaries separating regions with different modulation directions were observed. Such boundaries provide an additional interface giving rise to characteristic segments in macro twin boundaries. Detailed analysis of Ni-Mn-Ga single crystals reveals all possible {100)compound twin boundaries adjacent to macro twin boundaries. Different configurations of them are presented and discussed.