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.