This paper focuses on the processes of the occurrence of magnetization during structure formation in samples of Ni51Ti49 alloy under deformation conditions. The possibility of the existence of a phase with an FCC (face-centered cubic) lattice in titanium nickelide has been demonstrated by electron microscopy and electron diffraction. It has been discovered that the interplanar distances of BCC110 (body-centered cubic), FCC111, and HCP002 (hexagonal close packed) in the alloy under study have similar values, which indicates the possibility of their mutual polymorphic transformation. Based on the modular self-organization, a scheme of martensitic transformations in titanium nickelide from the B2 structure (BCC lattice) to the B19’ structure (HCP lattice) through an intermediate phase with an FCC lattice is proposed. It is shown that lenticular crystals appear in the Ni51Ti49 alloy under tensile deformation until rupture, which is accompanied by the onset of ferromagnetism. The effect of magnetization in Ni51Ti49 samples when immersed in liquid nitrogen has been also discovered. In this case, the reason for the appearance and disappearance of magnetization can be associated with microdeformation processes caused by direct and reverse martensitic transitions that occur during cooling and heating of the samples.
1 August 2008 in Bulletin of the Russian Academy of Sciences: Physics
The structure of intergranular interlayers in the 110G13L steel have been investigated. An increase in the lattice volume and occurrence of magnetization under dynamic load of samples quenched to austenite have been revealed.
Samples of Ni51Ti49 alloy subjected to plastic deformation have been studied. The microstructure was studied by transmission electron microscopy and microdifraction on a Hitachi 7700 microscope. The phase composition of the samples was determined by X-ray diffraction in a Bruker diffractometer. Magnetometric measurements were performed in an induction petlescope. Lenticular crystals (of the Ni2Ti3 phase containing bend–extinction contours indicating a significant curvature of the crystal lattice appearing in the localization zones of plastic deformation) were found in the deformation localization zones. It was revealed that the samples are non-magnetic before deformation, but after plastic deformation, they have non-zero magnetization, which is associated with the emergence of new phases. Under conditions of local curvature of the crystal lattice, special structural states arise in zones of increased interatomic distances, which increase the number of degrees of freedom in the deformable solid and thus contribute to the redistribution of the components of the initial solid solution and the appearance of new phases. It was shown that the crystalline structure of lenticular crystals is a phase constructed of a spinel structural type with a crystal lattice parameter of 11.53 ± 0.03 Å.