Dai Xue-Fang

Electronic structures and magnetisms of the Co2TiSb1−xSnx (x = 0, 0.25, 0.5) Heusler alloys: A theoretical study of the shape-memory behavior*

The total energy, electronic structures, and magnetisms of the AlCu2Mn-type Co2TiSb1−xSnx (x = 0, 0.25, 0.5) with the different lattice parameter ratios of c/a are studied by using the first-principles calculations. It is found that the phase transformation from the cubic to the tetragonal structure lowers the total energy, indicating that the martensitic phase is more stable and that a phase transition from austenite to martensite may happen at a lower temperature. Thus, a ferromagnetic shape memory effect can be expected to occur in these alloys. The AlCu2Mn-type Co2TiSb1−xSnx (x = 0, 0.25, 0.5) alloys are weak ferrimagnets in the austenitic phase and martensitic phase.

Successive phase transformation in ferromagnetic shape memory alloy Co37Ni34Al29 melt-spun ribbons ⁄

The martensitic transformation in Co37Ni34Al29 ribbon is characterized in detail by means of in-situ thermostatic x-ray difiraction and magnetic measurements. The results show a structural transition from the body-centred cubic to martensite with a tetragonal structure during cooling. Comparison between the results of the difiraction intensity with the magnetic susceptibility measurements indicates that the martensitic transformation takes place in several difierent steps during cooling from 273 to 163 K. During heating from 313 to 873 K, the peak width becomes very wide and the intensity turns very low. The ∞-phase (face-centred cubic structure) emerges and increases gradually with temperature increasing from 873 to 1073 K.