FEATURES OF THE B2 PHASE STRUCTURE CHANGE IN THE NiTi SURFACE LAYER AFTER PULSED ELECTRON-BEAM IMPACT

By X-ray diffraction, optical, scanning and transmission electron microscopy methods the structural-phase state of NiTi surface layers affected by low-energy high-current electron beams have been investigated. It was found that during treatment in recrystallized layer thickness of 8 – 10 μm a nonequilibrium single-phase structural state forms, which is characterized by a deformed B2 based phase structure, textured in a direction close to the <410>. The downstream with depths ranging from 10 to 20 μm layer except B2 phase with insignificant distortions of the crystal lattice contains a small volume fracture (up to 5 vol. %) of martensitic phase with В19′ structure. As a result of electron-beam treatment the modified layer chemical composition has changed to titanium enrichment due to Ti2Ni phase particles melting. At the same time intervals of martensitic transformations are shifted to higher temperatures thus even at room temperature can be expected that in the present layer the main structural state is martensitic. Using transmission electron microscopy the studies have showed that in the modified layer the martensitic phase is not observed. The assumption, explaining the created by a pulsed electron beam impact on the NiTi surface structure-phase state is expressed.

1. Ivanov Yu.F., Tsellermaer I.B., Rotshtein V.P., Gromov V.E. Electron-beam modifi cation of hardened steel. Fizicheskaya mezomekhanika. 2006. Vol. 9, no. 5, pp. 107–114. (In Russ.).

2. Zhang K.M., Zou J.X., Grosdidier T. etc. Journal of Alloys and Compounds. 2007, no. 434–435, pp. 682–685.

3. Meisner L.L. Mechanical and physico-chemical properties of alloys based on NiTi thin surface layers, modifi ed streams of charged particles. Fizicheskaya mezomekhanika. 2004. Vol. 7, no. 2. Spec., pp. 169–172. (In Russ.).

4. Meisner L.L., Lotkov A.I., Mironov Yu.P., Neiman A.A. Hindawi Publishing Corporation. Journal of Nanotechnology. 2010. Vol. 2010, pp. 1–8.

5. Uglov V.V., Kuleshov A.K., Soldatenko E.A., Koval N.N., Ivanov Yu.F., Teresov A.D. Surface and Coatings Technology. 2012. Vol. 206, no. 11–12, pp. 2972–2976.

6. Grosdidier T., Zou J.X., Bolle B., Hao S.Z., Dong C. Journal of Alloys and Compounds. 2010. Vol. 504, pp. 508–511.

7. Neiman A.A., Meisner S.N., Lotkov A.I., Meisner L.L. Increase of microhardness and fracture in the surface layers of NiTi by changing the parameters of electron-beam exposure. Perspektivnye materialy. 2007. Spec. issue. Vol. 2, pp. 429–431. (In Russ.).

8. Takayuki Yoneyama, Shuichi Miyazaki. Shape memory alloys for biomedical applications. CRC Press, Cambridge, England, 2009. 378 p.

9. Meisner L.L., Lotkov A.I., Sivoha V.P., Turova A.I., Barmina E.G. Effects of surface modifi cation, structure and phase composition on corrosion properties of TiNi based alloys. Fizika i khimiya obrabotki materialov. 2003. Vol. 1, pp. 83–89. (In Russ.).

10. Meisner L.L., Nikonova I.V., Lotkov A.I. Razdorskii V.V., Kotenko M.V. Effect of ion-and electron-beam surface modifi cation on the corrosion properties and biocompatibility NiTi experiments in vivo. Perspektivnye materialy. 2008, no. 3, pp. 15–27. (In Russ.).

11. Meisner L.L., Lotkov A.I., Rotshtein V.P., Mironov Yu.P., Meisner S.N. Neiman A.A. Formation of alloyed layers with nano- and submicrocrystalline structure on the surface of NiTi upon irradiation with pulsed electron beams. Fizika i khimiya obrabotki materialov. 2011, no. 4, pp. 36–43. (In Russ.).

12. Il’inyh N.I., Kulikova T.V., Moiseev G.K. Sostav i ravnovesnye kharakteristiki metallicheskikh rasplavov binarnykh sistem na osnove zheleza, nikelya i alyuminiya [Composition and equilibrium characteristics of metal melts of binary systems based on iron, nickel and aluminum]. Ekaterinburg: UrO RAN, 2006. 235 p. (In Russ.).

13. Me isner L.L., Lotkov A.I., Ostapenko M.G., Gudimova E.Yu. Analy sis by X-ray diffraction of the gradient of the internal stresses in titanium nickelide after electron beam surface treatment. Fizicheskaya mezomekhanika. 2012. Vol. 15, no. 3, pp. 79–89. (In Russ.).

14. Meisner L.L., Lotkov A.I., Ostapenko M.G., Gudimova E.Yu. Appl. Surf. Science. 2013. Vol. 280, pp. 398–404.

15. Testardi L., Veger M., Gol’dberg I., Gor’kov L.P. Sverkhprovodyashchie soedineniya so strukturoi β-vol’frama [Superconducting compounds with β-tungsten structure]. Moscow: Mir, 1977. 435 p. (In Russ.).

16. Kornilov I.I., Belousov O.K., Kachur E.V. Nikelid titana i drugie splavy s effektom “pamyati”. [Titanium nikelide and other alloys with a “memory” effect]. Moscow: Nauka, 1977. 177 p. (In Russ.).

17.