| Abstract |
This paper describes the results of a study that looked at the microstructure, phase composition and mechanical properties of a binary powder alloy of TiNi (55.5 % (wt) Ni) at different stages of deformation induced by helical rolling at 1,000 oC . Inconsistent sectional grain structures were found in the specimens with the following degrees of deformation — ε = 0.09, 0.3 and 0.6: The surface layers would form finer grains while the core would have a coarser grain structure. In the specimens that were subjected to sintering and slight deformation (ε = 0.09; 0.3; 0.6), pores were found of a close-to-spherical shape. Deformation (ε = 0.8) helps cure bigger pores. At the same time, it leads to smaller ellipsoidal pores occurring in the core layers. Durometric and metallographic studies showed that, before ε = 0.3, the relative density of the alloy rose while its porosity decreased. However, as the reduction degree grew to ε = 0.8, the core of the specimens would form a porous structure. Deformation to ε = 0.3 does not lead to any significant change in the average grain size compared with the as-sintered state. Finer grains were not observed until the deformation reached ε = 0.6, and when the deformation is further increased to ε = 0.8, a consistent grain structure is formed with the average grain size of 64 μm. It is shown that the structure of the powder alloy of NiTi after deformation includes a B2 austenitic phase, and the deformation of ε = 0.8 can result in up to 10 % of R-martensite formed, which is probably caused by a shift of the martensitic transformation points towards the high temperature region. The deformation of ε = 0.8 leads to increased strength and ductility of the alloy compared with the as-sintered state. However, the resultant ductility does not meet the TU 1-809-394–84 specification applicable to the ТН1 alloy grade. So, the deformation of ε = 0.8 by helical rolling produces a consistent sectional grain structure but creates localized porosity in the core, which is one of the causes of low ductility. In order to improve ductility, it is recommended to apply higher degrees of deformation and optimised regimes of helical rolling. This could help form finer grains and eliminate porosity in the core thus improving ductility. The results of implementing the above recommentations are described in the second part of the research paper.
This research was funded by the Russian Foundation for Basic Research (Project No. 17-03-00360 А). |
| References |
1. Van Humbeeck J. Non-medical applications of shape memory alloys. Materials Science and Engineering. 1999. Vol. 273–275. pp. 134–148.
2. Otsuka K., Ren X. Recent developments in the research of shape memory alloys. Intermetallics. 1999. Vol. 273–275. pp. 134–148.
3. Otsuka K., Ren X. Physical metallurgy of Ti–Ni-based shape memory alloys. Progress in Materials Science. 2005. No. 50. pp. 511–678.
4. Yamada K., Matsui R. Improvement of Corrosion Fatigue Strength for TiNi Shape Memory Alloy. Key Engineering Materials. 2017. Vol. 725. pp. 389–393.
5. Soba R., Tanabe Y., Yonezawa T., Umeda J., Kondoh K. Effect of Shape Memory Heat Treatment on Microstructures and Mechanical Properties of Powder Metallurgy TiNi Shape Memory Alloy. Materials Transactions. 2018. Vol. 59. pp. 805–810.
6. Misochenko A. et al. Microstructure Evolution and Mechanical Behavior in Shape Memory Nanostructured TiNi Alloy. Defect and Diffusion Forum. 2018. Vol. 385. pp. 169–174.
7. Song G., Ma N., Li H.-N. Applications of shape memory alloys in civil structures. Engineering Structures. 2006. Vol. 28. pp. 1266–1274.
8. Hartl D., Lagoudas D., Mabe J., Calkins F. Use of a Ni60Ti shape memory alloy for active jet engine chevron application: I. Thermomechanical characterization. Smart Materials and Structures. 2009. Vol. 19. pp. 15–20.
9. Makino E., Mitsuya T., Shibata T. Fabrication of TiNi shape memory micropump. Sensors and Actuators A: Physicals. 2001. Vol. 88. pp. 256–262.
10. Abadie J., Chaillet N., Lexcellent C. Modeling of a new SMA microactuator for active endoscopy applications. Mechatronics. 2009. Vol. 19. pp. 437–442.
11. Sheng J., Desai J. P. Design, modeling and characterization of a novel mesoscale SMA-actuated torsion actuator. Smart Materials and Structures. 2015. Vol. 24. pp. 105005.
12. Ibrahim M. K., Hamzah E., Saud S. N., Nazim E. M. Powder Metallurgy Fabrication of Porous 51(at.%)Ni-Ti Shape Memory Alloys for Biomedical Applications. Shape Memory and Superelasticity. 2018. Vol. 4. pp. 327–336.
13. Kuribayashi K., Tsuchiya K., You Z. et al. Self-deployable origami stent grafts as a biomedical application of Ni-rich TiNi shape memory alloy foil. Materials Science and Engineering: A. 2006. Vol. 419. pp. 131–137.
14. Ilyin A. A., Kollerov M. Yu., Khachin V. I., Gusev D. A. Medical instruments and implants from titanium nickelide: Metals, technology, application. Metally. 2002. No. 3. pp. 105–110.
15. Kollerov M. Yu., Ilyin A. A., Polkin I. S., Faynbron A. S., Gusev D. E., Khachin S. V. Structural aspects in the production of semi-finished products from titanium nickelide alloys. Metally. 2007. No. 5. pp. 77–85.
16. Zhang Z. et al. Vacuum Induction Melting of TiNi Alloys Using BaZrO3 Crucibles. Materials Science Forum. 2013. Vol. 765. pp. 316–320.
17. Badakhshan Raz S., Sadrnezhaad S. K. Effects of VIM frequency on chemical composition, homogeneity and microstructure of NiTi shape memory alloy. Materials Science and Technology. 2004. Vol. 20. pp. 593–598.
18. Kotsar M. L., Kaplenkov V. N., Alekberov Z. M. Obtaining the high-pure titanium based alloys. Investigation of their composition and properties. Tsvetnye Metally. 2017. No. 6. pp. 84–93.
19. McNeese M. D., Lagoudas D. C., Pollock T. C. Processing of TiNi from elemental powders by hot isostatic pressing. Materials Science and Engineering: A. 2000. Vol. 280. pp. 334–348.
20. Terayma A., Kyogoku H., Sakaruma M., Komatsu S. Fabrication of TiNi Powder by Mechanical Alloying and Its Shape Memory Characteristics of Sintered Alloy. Journal of the Japan Institute of Metals and Materials. 2005. Vol. 69. pp. 523–529.
21. Hey J. C., Jardine A. P. Shape memory TiNi synthesis from elemental powders. Materials Science and Engineering: A. 1994. Vol. 188. pp. 291–300.
22. Che H. Q., Ma Y., Fan Q. Ch. Investigation of the mechanism of selfpropagating high-temperature synthesis of TiNi. Journal of Materials Science. 2011. Vol. 46. pp. 2437–2444.
23. Yang Y., Zhang C., Yang Y., Chen L. Laser induced self-propagating high-temperature synthesis of TiNi alloy. Chinese Optics Letters. 2005. Vol. 3. pp. 35–37.
24. Shiva S., Palani L. A., Mishra S. K., Paul C. P., Kukreja L. M. Investigations on the influence of composition in the development of Ni – Ti shape memory alloy using laser based additive manufacturing. Optics & Laser Technology. 2015. Vol. 69. pp. 44–51.
25. Haberland C., Elahinia M., Walker J. M., Meier H., Frenzel J. On the development of high quality NiTi shape memory and pseudoelastic parts by additive manufacturing. Smart Materials and Structures. 2014. Vol. 23. pp. 104002.
26. Shishkin S. V., Makhutov N. A. Design of load carrying structures made from shape memory alloys. Izhevsk : NITS Regulyarnaya i khaoticheskaya dinamika, 2007. 412 p.
27. Shuytsev A. V. The structure and performance of the TiNi intermetallic compound produced by sintering of calcium hydride powders: thesis of Dissertation ... of Candidate of Chemical Sciences. Moscow, 2015. 19 p.
28. Kasimtsev A. V., Markova G. V., Shuytsev A. V., Levinsky Yu. V., Sviridova T. A., Alpatov A. V. Structural changes during consolidation of TiNi calcium hydride powders. Metallurg. 2014. No. 11. pp. 108–114.
29. Kasimtsev A. V., Levinsky Yu. V. Calcium hydride powders of metals, intermetallic and heat-resistant compounds and composites. Moscow : MITKhT, 2012. 247 p.
30. Markova G. V., Kasimtsev A. V., Shuytsev A. V., Sviridova T. A. Structural patterns of sintered TiNi intermetallic compound. Materialovedenie. 2015. No. 3. pp. 31–35.
31. Kasimtsev A. V., Markova G. V., Shuytsev A. V., Levinsky Yu. V., Sviridova T. A., Alpatov A. V. Powdered calcium hydride TiNi intermetallic compound. Izvestiya vuzov. Poroshkovaya metallurgiya i funktsionalnye pokrytiya. 2014. No. 3. pp. 31–37.
32. Polukhin P. I. Technology of metals and other structural materials. Moscow : Vysshaya shkola, 1997. 464 p.
33. Derevyagina L. S., Gordienko A. I., Pochivalov Yu. I., Smirnova A. S. Modification of the Structure of Low-Carbon Pipe Steel by Helical Rolling, and the Increase in Its Strength and Cold Resistance. Physics of Metals and Metallography. 2018. Vol. 119. pp. 83–91.
34. Wang Q., Wang Q., Xiao J. Study on the method for groove design in the helical rolling of steel balls. Journal of Materials Processing Technology. 1995. Vol. 55. pp. 340–344.
35. Prokoshkin S. D., Brailovskii V., Khmelevskaya I. Yu. et al. Creation of substructure and nanostructure in thermomechanical treatment and control of functional properties of Ti – Ni alloys with shape memory effect. Metal Science and Heat Treatment. 2005. Vol. 47. pp.182–187.
36. Lotkov A., Grishkov V., Kashin O., Baturin A., Timkin V., Zhapova D. The Influence of Warm Deformation on the Structure and Martensitic Transformations in TiNi-Based Alloys. AIP Conference Proceedings. 2014. Vol. 1623. pp. 355–358.
37. Kolobova A. Yu., Ryklina E. P., Prokoshkin S. D., Inaekyan K. E., Brailovskii V. Study of the Evolution of the Structure and Kinetics of Martensitic Transformations in a Titanium Nickelide upon Isothermal Annealing after Hot Helical Rolling. Materials Science and Engineering: A. 2018. Vol. 734. pp. 445– 452.
38. GOST 5639–82. Steels and alloys. Methods of measuring the grain size (incl. Revision No. 1). Moscow : Izdatelstvo standartov, 1983. 21 p. Introduced: 01.01.1983.
39. GOST 9450–76. Measurements microhardness by diamond instruments indentation. Moscow : Izdatelstvo standartov, 1976. 32 p. Introduced: 01.01.1977.
40. GOST 18898–89 (ISO 2738–87). Powder products. Methods for determination of density, oil content and porosity. Moscow : Izdatelstvo standartov, 1990. 10 p. Introduced: 01.01.1990.
41. GOST 1497–84. Metals. Methods of tension test (incl. Revisions No. 1, 2, 3). Moscow : Standartinform, 2008. 22 p. Introduced: 01.01.1986. |
