Skip to main content

Influence of Ultrafine-Grained Structure on the Kinetics and Fatigue Failure Mechanism of VT6 Titanium Alloy

Abstract

The kinetics and mechanism of fatigue failure of the VT6 titanium alloy (composition, wt %: 5.95 V, 5.01 Al, 89.05 Ti) in the initial (hot-rolled) coarse-grained (CG) state and after equal-channel angular pressing (ECAP) in the ultrafine-grained state (UFG) are investigated. ECAP is performed using billets of the mentioned alloy 20 mm in diameter and 100 mm in length preliminarily subjected to homogenizing annealing. Then, quenching in water is performed from 960°C with holding for 1 h, tempering at 675°C for 4 h, and ECAP at 650°C (route Bс, φ = 120°, number of passes n = 6). The fine alloy structure after ECAP is investigated by transmission electron microscopy at an accelerating voltage of 200 kV. To determine alloy hardness, a Time Group TH 300 hardness meter is used. Static tensile tests are performed for round samples 5 mm in diameter using a Tinius Olsen H50KT universal testing machine. The extension velocity is 5 mm/min. Fatigue tests are performed using prismatic samples 10 mm in thickness at 20°C according to the three-point bending test using an Instron 8802 installation. It is shown that, under the same loading conditions, the fatigue life of alloy samples (the number of cycles before failure) in the initial CG state is higher than that of the alloy samples in the UFG state. It is shown that the number of cycles before fatigue-crack nucleation was at a level of 19–23% of the total sample longevity, regardless the alloy state. The straight-linear segment in kinetic diagrams of the alloy fatigue failure is approximated by the Paris equation. It is revealed that the propagation rate of the fatigue crack in the alloy with an UFG structure is somewhat higher than in the alloy with a CG structure. The microrelief of fatigue cleavages of the VT6 alloy both in the CG and UFG state can be characterized as scaly with fatigue grooves on the scale surface. A low-relief region 4–6 μm in length can be observed in the failure region of the samples with an UFG structure. The microrelief of the rupture region is pit, irrespective of the alloy state.

This is a preview of subscription content, access via your institution.

Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.

REFERENCES

  1. 1

    Chung, C.S., Kim, J.K., Kim, H.K., and Kim, W.J., Improvement of high-cycle fatigue life in a 6061 Al alloy produced by equal channel angular pressing, Mater. Sci. Eng. A, 2002, vol. 337, pp. 39–44.

    Article  Google Scholar 

  2. 2

    Vinogradov, A., Nagasaki, S., Patland, V., Kitagawa, K., and Kawazoe, M., Fatigue properties of 5056 Al–Mg alloy produced by equal–channel angular pressing, Nanostruct. Mater., 1999, vol. 11, pp. 925–934.

    Article  Google Scholar 

  3. 3

    Furuya, Y., Matsuoka, S., Shimakura, S., Hanamura, T., and Torizuka, S., Effects of carbon and phosphorus addition on the fatigue properties of ultrafine-grained steels, Scripta Mater., 2005, vol. 52, pp. 1163–1167.

    Article  Google Scholar 

  4. 4

    Okayasu, M., Sato, K., Mizuno, M., Hwang, D.Y., and Shin, D.H., Fatigue properties of ultra-fine grained dual phase ferrite/martensite low carbon steel, Int. J. Fatigue, 2008, vol. 30, pp. 1358–1365.

    Article  Google Scholar 

  5. 5

    Meyer, L.W., Sommer, K., Halle, T., and Hockauf, M., Crack growth in ultrafine grained AA6063 produced by equal–channel angular pressing, J. Mater. Sci. Eng., 2008, vol. 43, pp. 7426–7431.

    Google Scholar 

  6. 6

    Meyer, L.W., Sommer, K., Halle, T., and Hockauf, M., Microstructure and mechanical properties affecting crack growth behaviour in AA6060 produced by equal–channel angular extrusion, Mater. Sci. Forum, 2008, vols. 584–586, pp. 815–820.

  7. 7

    Estrin, Y. and Vinogradov, A., Fatigue behaviour of light alloys with ultrafine grain structure produced by severe plastic deformation: An overview, Int. J. Fatigue, 2010, vol. 32, pp. 898–907.

    Article  Google Scholar 

  8. 8

    Goto, M., Yamamoto, T., Kitamura, J., Iwamura, T., Han, S.Z., Ahn, J.-H., Kim, S., and Lee, J., Crack growth rate of inclined and deflected surface-cracks in round-bar specimens of copper processed by equal channel angular pressing under cyclic loading, Eng. Fract. Mech., 2017, vol. 182, pp. 100–113.

    Article  Google Scholar 

  9. 9

    Estrin, Y. and Vinogradov, A., Extreme grain refinement by severe plastic deformation: A wealth of challenging science, Acta Mater., 2013, vol. 61, pp. 782–817.

    Article  Google Scholar 

  10. 10

    Mughrabi, H., Hoppel, H.W., and Kautz, M., Fatigue and microstructure of ultrafine-grained metals produced by severe plastic deformation, Scripta Mater., 2004, vol. 51, pp. 807–812.

    Article  Google Scholar 

  11. 11

    Wang, K., Tao, N.R., Liu, G., Lu, J., and Lu, K., Plastic straininduced grain refinement at the nanometer scale in copper, Acta Mater., 2006, vol. 54, pp. 5281–5291.

    Article  Google Scholar 

  12. 12

    Millett, P.C., Selvam, R.P., and Saxena, A., Stabilizing nanocrystalline materials with dopants, Acta Mater., 2007, vol. 55, pp. 2329–2336.

    Article  Google Scholar 

  13. 13

    Khalaj, G., Khalaj, M.J., and Nazari, A., Microstructure and hot deformation behavior of AlMg6 alloy produced by equal-channel angular pressing, Mater. Sci. Eng. A, 2012, vol. 542, pp. 15–20.

    Article  Google Scholar 

  14. 14

    Skryabina, N.E., Pinyugzhanin, V.M., and Frushar, D., Features of the deformation texture formation in the AZ31 magnesium alloy during equal-channel angular pressing, Perspekt. Mater., 2013, no. 1, pp. 33–42.

  15. 15

    Islamgaliev, R.K., Nesterov, K.M., Khafizova, E.D., Ganeev, A.V., Golubovskii, E.R., and Volkov, M.E., Strength and fatigue of the AK4-1 ultrafine-grained aluminum alloy, Vestn. UGATU, 2012, no. 8, pp. 104–109.

  16. 16

    Valiev, R.Z., Semenova, I.P., Latysh, V.V., Shcherbakov, A.V., and Yakushina, E.B., Nanostructural titanium for biomedical applications: new developments and prospects of commercialization, Ross. Nanotekhnol., 2008, nos. 9–10, pp. 80–89.

  17. 17

    Klevtsov, G.V., Valiev, R.Z., Botvina, L.R., Klevtsova, N.A., Semenova, I.P., Kashapov, M.R., Fesenyuk, M.V., and Soldatenkov, A.P., Kinetics of fatigue fracture of titanium in a submicrocrystalline state, Vestn. OGU, 2012, no. 9, pp. 123–125.

  18. 18

    Valiev, R.Z., Zhilyaev, A.P., and Langdon, T.G., Bulk Nanostructured Materials: Fundamentals and Applications, TMS-Wiley, 2014.

    Google Scholar 

  19. 19

    Valiev, R.Z., Raab, G.I., Gunderov, D.V., Semenova, I.P., and Murashkin, M.Yu., Development of methods of intense plastic deformation to form bulk nanostructured materials with unique mechanical properties, Nanotekhnika, 2006, no. 2, pp. 32–42.

  20. 20

    Klevtsov, G.V., Bobruk, E.V., Semenova, I.P., Klevtsova, N.A., and Valiev, R.Z., Prochnost’ i mekhanizmy razrusheniya ob’’emnykh nanostrukturirovannykh metallicheskikh materialov: Uchebnoe posobie (Durability and Destruction Mechanisms of Bulk Nanostructured Metal Materials: Textbook), Ufa: Ufimsk. Gos. Aviats. Tekh. Univ., 2016.

  21. 21

    Klevtsov, G.V., Botvina, L.R., Klevtsova, N.A., and Limar’, L.V., Fraktodiagnostika razrusheniya metallicheskikh materialov i konstruktsii (Fractography of Fracture of Metallic Materials and Constructions), Moscow: MISiS, 2007.

Download references

Author information

Affiliations

Authors

Corresponding authors

Correspondence to G. V. Klevtsov, R. Z. Valiev, I. P. Semenova, N. A. Klevtsova, V. A. Danilov, M. L. Linderov or S. V. Zasypkin.

Additional information

Translated by N. Korovin

About this article

Verify currency and authenticity via CrossMark

Cite this article

Klevtsov, G.V., Valiev, R.Z., Semenova, I.P. et al. Influence of Ultrafine-Grained Structure on the Kinetics and Fatigue Failure Mechanism of VT6 Titanium Alloy. Russ. J. Non-ferrous Metals 60, 253–258 (2019). https://doi.org/10.3103/S1067821219030088

Download citation

Keywords:

  • fatigue failure
  • titanium alloy
  • failure kinetics and mechanism
  • coarse-grained (CG) state
  • ultrafine-grained (UFG) state
  • ECAP
  • Paris’s equation