Effect of titanium alloying on the structure, the phase composition, and the thermoelastic martensitic transformations in ternary Ni-Mn-Ti alloys

摘要

The behavior and the properties of Ni50Mn50-y Ti (y) (y = 5, 10, 15, 25, 30) alloys are studied by electrical resistivity measurements, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction over a wide temperature range. It is found that the martensite transformation temperature of the complex alloys can be significantly lower than the transformation temperature range of binary Ni50Mn50 and Ni49Mn51 alloys. Apart from tetragonal L1(0) martensite, a complex multilayer (10M) crystal lattice is revealed in the alloys. Martensite is shown to have a predominant morphology in the form of hierarchic packets of thin coherent plates of nanoand submicrocrystalline crystallites, which have plane habit boundaries. In the case of tetragonal L1(0) and 10M martensite, these boundaries are close to {011} (B2) and are pairwise twinned along one of the 24 equivalent twinning shear systems.