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Effect of rare earth Dy addition on microstructure and martensitic transformation of polycrystalline Ni50Mn29Ga21−xDyx ferromagnetic shape memory alloys

School of Materials Science and Engineering, P.O. Box 405, Harbin Institute of Technology, Harbin 150001, China
Materials Science and Engineering: A 01/2006; DOI:10.1016/j.msea.2006.02.190

ABSTRACT The effects of rare earth Dy addition on microstructure and martensitic transformation of polycrystalline Ni50Mn29Ga21−xDyx (numbers indicate at.%) shape memory alloys were investigated by means of scanning electron microscopy, energy dispersive X-ray spectroscopy, differential scanning calorimetry and X-ray diffraction. The results show that the microstructure of Ni–Mn–Ga–Dy alloys consists of the matrix and Dy-rich phase. Small amounts of the Dy-rich phase with 0.1 at.% Dy disperse homogeneously in the matrix. With the increase of the Dy content, the Dy-rich phase becomes larger and trends to distribute along the grain boundaries. The one-step martensitic transformation is observed in Ni50Mn29Ga21−xDyx alloys. With increasing Dy content, the martensitic transformation temperatures of Ni50Mn29Ga21−xDyx alloys increase remarkably, whereas the martensite structure of the Dy-containing alloys appears to be unchanged exhibiting seven-layered martensite structures at room temperature.

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L. Gao