M. A. Khusainov, Yaroslav the Wise Novgorod State University, Velikiy Novgorod, Russia; V. A. Andreev, Industrial center "MATEKS", Moscow, Russia; A. B. Bondarev, Industrial center “MATEKS”, Moscow, Russia
The researches were carried out at the alloy-wire of Ti-50,8 àò% Ni after cold drawing.
The thermomechanical processing (TMP) included the deformation of the through-pass tubular furnace at 500-700°Ñ, and then at 300-400°Ñ. The first batch of wire-samples, after TMP, was tested on the fatigue according to the one-sided bend scheme. The second group of the samples deformed after TMP on the base of the plateau-shaped part of the phase flowability with partial discharges. They were also tested at the room-temperature fatigue (18-22)°Ñ. Pseudoelasticity effect was estimated by the amount of full pseudoelastic return deformation (epe).
It is ascertained that TMP provided epe = 8-9% and 2010 cycles before destroying without any processing of the wire surface. After TMP and preliminary mechanical cycling by e = 4% during 15-25 cycles (at the first stage), the durability (ïF) was increasing till 2275 cycles, while after 50 cycles it decayed markedly (ïF = 1820 ö). Thermomechanical processing and following stressing along with partial discharging intensified pseudoelastic return of deformation, stimulating the formation of the expressed pseudoelasticity of the swinging-vane type on the level e = 9-10% by the durability of 2614 cycles. The results of the systematic researches at the given issue are presented in the paper.
Summary: After cold wire drawing the thermomechanical treatment (TMT) was carried out for the purpose of forming the straightness and pseudoelasticity. On the first operation the wire was subjected to the double deformation by tensile at 500-700°Ñ and 300-400°Ñ. The full pseudoelastic deformation return was provided at the level 8-9% and the number of cycles till the fracture (ïF = 2010 ö). Then preliminary mechanical cycling according to the asymmetrical bend scheme by E = 4% during 15-25 cycles was carried out. The process was finished with testing for the fatigue at Eèçã = 5%, ïF = 2275 ö.
On the second operation the wire after TMP was subjected to the loading along with partial unloading. As a result, pseudoelastic deformation has increased till 9-10%, and durability – till 2614 cycles.
