MARTENSITIC TWINS REORIENTATION AND STRESS-STRAIN BEHAVIOR OF FERROMAGNETIC SHAPE MEMORY ALLOYS Ni-Mn-Ga SINGLE CRYSTALS
铁磁形状记忆合金Ni-Mn-Ga单晶的马氏体孪晶再取向应力应变行为

Ferromagnetic shape memory alloys Ni53Mn23.5Ga23.5, Ni54Mn23Ga23 and Ni50Mn27-Ga23 single crystals were prepared by zone-melting unidirectional solidification. The orientations of the cut single crystals were determined by X-ray diffraction method. The Ni-Mn-Ga crystal growth direction is along 100] with the deviation less than 5 circ. The martensitic twins reorientation process was detected by the stress-strain curves. The compression experiments along different directions were performed, respectively. The results show that the compression improves the texture of favorable martensitic variants and turns them into a single martensitic variant by martensite reorientation.