M. A. Khusainov, N. V. Petrov, Yaroslav the Wise Novgorod State University, Velikiy Novgorod, Russia; A. B. Bondarev, Industrial center “MATEKS”, Moscow, Russia; V. A. Andreev, Industrial center "MATEKS", Moscow, Russia
It is shown that heat of the wire (Ø 0,4 mm) deformed by drawing causes strain relief (6-7%), so the length of the sample decreases. The behavior can be explained by formation of the oriented stress-assisted martensite at cold drawing, which influences the ability of the alloy to restore its shape at heating. The applied tensile stress to 150-200 MPa (σ > σM) does not cause stretching of the sample. So it is impossible to create the conditions of deformation by means of the plasticity of the wire.Repeated mechanical-thermal treatment (RMTT) of the wire samples with realization of the effect of generation of reactive voltage at deformation 6-8% and subsequent pulse heating causes on the one hand enhanced strain accumulation along the line of the applied load, and on the other hand it causes development of the two-way effect on cooling. Pulse heating to 800-900oC with a partial relaxation of internal stresses causes narrowing of the interval of the martensitic transformation. The effect of the reversibility of deformation caused by martensitic reaction force B2 ↔ B19′, is initiated by small values of the applied stresses (σ = 25-50 MPa).
As a result the optimum regiment of RMTT is found out, under which the reversible SME is formed and it is reproduced invariably at thermal cycling.
Summary: Repeated mechanical-thermal treatment (RMTT) of the wire samples causes enhanced strain accumulation along the line of the applied load, and the development of the two-way effect on cooling.
