Anisotropy of Young's modulus,shear modulus,and Poisson's ratio for the B2-phase of a Ti50Ni48Fe2 single crystal under hydrostatic compression conditions up to 0.6 GPa

We present calculations of Young's modulus, the shear modulus, and Poisson's ratio as a function of direction in the (100) and (110) planes of the B2 phase of a Ti₅₀Ni₄₈Fe₂ single crystal. The calculations were done on the basis of our measurements of the velocities of transverse and longitudinal ultrasonic waves propagating in the indicated alloy at atmospheric pressure and for a hydrostatic pressure of 0.6 GPa at a temperature of 298 K. We have shown that in contrast to the effect of temperature, as the pressure is reduced along the pathway to the martensitic transformation B2 R, application of pressure to the alloy found in the same pretransitional state increases the anisotropy of the crystal lattice.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 45–49, March, 1995.     

Premartensitic and martensitic transformations in Ti49Ni51 single crystal: Ageing effect

The influence of isochronous annealing on the phase composition, long-range atomic-order parameter S in the B2 phase, premartensitic structure, and martensitic transformation sequence and temperatures in a Ti₄₉Ni₅₁ single crystal was studied by X-ray and neutron-diffraction. Ageing the test alloy was found to bring about concurrent changes in the type of the intermediate shear structure involved and in the sequence of martensitic transormations in the premartensitic temperature range studied. The increase in the order parameter for the B2 phase was most pronounced in passing from the zonal stage of ageing to the growth stage of the Ti₃Ni₄ precipitates, as revealed by X-ray diffraction. No apparent correlation between the type of the premartensitic structure, R-transformation temperature, and order parameter variations was observed. At the same time, the martensite start temperature into the B19′ phase was directly proportional to variations in S. Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences. Institute of Physics of Metals, Urals Division of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 64–70, July, 1999.     

Influence of aging on the temperature of the beginning of a martensitic transformation in the intermetallide TiNi

The influence of aging at 250°C on the temperature of the beginning of a martensitic transformation in the alloy Ti + 51 at.% Ni is investigated after tempering from 600 and 800°C, as well as after preliminary thermal cycling. The temperature dependence of the electrical resistivity, x-ray diffraction analysis, and low-angle neutron scattering (LNS) were used as investigation methods. It is detected that M_s varies along the curve with a minimum which is at 1.5 h of annealing. The total effect of reducing M_s threefold exceeds the influence of thermal cycling. The LNS is observed 1.5 h after annealing, which indicates the origination of concentration inhomogeneities in the alloy. The M_s reduction stage is related to formation of zones with insignificant disturbances of the crystalline lattice of the matrix, and the stage of its magnification is related to liberation of particles of new nickelenriched phase.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 11–16, October, 1982.     

Plastic deformation and fracture of polycrystalline Ni–Ti with stress concentrators of different scales

Stress concentrators of different scales inherent in polycrystals tend to form mesosubstructures under load. Television-optical images of displacements are obtained for the Ni–Ti alloy to study the deformation and fracture behavior. Discussed are similarity laws in connection with the formation of dissipative structures at the micro- and macro-scale level.