24September2017

Materials and Electronics Engineering

Structure phase states formation of Ti-Y surface layer by electro explosion and electron-beam treatment

V.E. Gromov1*, K.V. Sosnin1, Yu.F. Ivanov2, 3, X.L. Wang4, M.S. Liu5, Y. Wu4, E.S. Ivanova1, S.A. Nevskii1

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1Siberian State Industrial University, Novokuznetsk, Russia
2Institute of High Current Electronics, SD RAS, Tomsk, Russia
3National Research Tomsk State University, Tomsk, Russia
4Research Institute, Northeastern University, Shenyang, China
5Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang, China

Materials and Electronics Engineering 20152:3

Publication Date (Web): October 8, 2015 (Article)

DOI:10.11605/mee-2-3

*Corresponding author. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Abstract

 


Figure 6 Lamellar eutectic formed in the adjacent region between Ti-rich and Y-rich zones.

A titanium-yttrium composite surface layer is formed on pure titanium surface by electro explosion and electron-beam treatments. The composite consists of titanium-rich and yttrium-rich eutectic microstructures. Both eutectics are in non-equilibrium state with their chemical constitution deviation from that in equilibrium phase diagram. The surface layer increases the surface hardness by three times, decreases the friction coefficient by 3 times and reduces the ware rate by 4 times in comparison with that of the surface of pure titanium.


 

Keywords

Surface layer, Electric explosion, Electron beam, Wear property

 

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Introduction

    According to the equilibrium titanium (Ti)-yttrium (Y) phase diagram [1], there is a miscibility gap in liquid state when the composition of yttrium (Y) in the solution is between 30 to 81 atomic %. And a phase separation in liquid would form two eutectic compositions. When the temperature is below 1155K, the material is presented by a mixture of two phases with α-Ti and α-Y. However, due to the low solubility of yttrium and titanium in solid state, the lattice constants of the hexagonal crystals of α-Ti and α-Y vary insignificantly in the alloys [1]. Thus, Ti-Y refers to the binary systems with negligible solubility and has no intermetallic compounds formable. On the basis of the available knowledge of this type of alloys, a significant research interests has been attracted to improve the mechanical properties of the alloys [2, 3]. One of the ideas is to fabricate the materials in which the solubility of one element into another phase can exceed the equilibrium limitation. This gives the possibility to fabricate the materials with notably high physical and mechanical properties [3, 4].

    Up to now, there have been many methods and treatments toward the modification and improvement of structure and property of surface layer of metals and alloys [5, 6]. Meanwhile, the duplex treatment including the electro explosion alloying (EEA) followed by electron-beam treatment (EBT) is of one of them. EEA helps to generate surface saturation using conductor explosion [5, 6]. EBT utilizes high intensity pulsed electron beams. It is possible to control and regulate the supply energy in EBT to generate a desirable energy distribution in the surface and subsurface of the material to achieve the desirable effect [7-10]. The high localized heating rate and subsequent high cooling rate enables the formation of amorphous, nanostructured and submicron structured crystalline surface layer [11]. Many properties, e.g. the fatigue life of stainless steels, have been found improved significantly by having surface with those microstructures [12-15]. The aim of this work is the analysis of structure-phase states and properties of technical pure Ti surface layer subjected to electro-explosive alloying by Y and following electron beam treatment.

Experiments

    Technically pure titanium with a grade name VT 1-0 (F£0.25 wt. %, C£0.07 wt. %, Si£0.04 wt. %, O£0.02 wt. %, and H£0.01 wt. %) is used as a base material [16]. The formation of Ti-Y surface layer is done by two stage processes. The first stage implements EEA [17]. A foil being made of 100 mg titanium VT 1-0 is selected as current-carrying materials to achieve electro explosion. 400 g yttrium powders whose dimensions are in nanometer scale are placed in the region of explosion. The plasma effect time on the sample surface is around 100 ms. The absorbed density of power on the axis of jet is around 5.5 GW/m2. The pressure in the near-surface layer is 12.5 MPa. The residual gas pressure in the working chamber is around 100 Pa. The plasma temperature at the outlet of nozzle is around 104 K. The surface alloy thickness is 30 mm. The thickness of heat effect zone is 50 mm. The second stage implements the high intensity pulse electron beam in SOLO-device for high-speed heat treatment of the alloy [7]. It is estimated that for the duration of electron beam acting on metal surface in 50-200 ms the heating and cooling rates at the modified layer are around 106 K/s. The irradiation parameters include energy of electrons 18 KeV, energy density of electron beam 20 J/cm2, pulse duration 150 ms, number of pulse 3, and pulse repetition frequency 0.3 Hz. The microstructure and chemical constitutions in phases are characterized by optical microscope, scanning electron microscope and X-ray diffractions [18]. The tribological properties of the surface are measured in dry friction using scheme disc-ball (counterbody-ball with of 3 mm diameter made by solid alloy WC-Co at loading-1H). The hardness is measured using a hardness tester PMT-3. 

Results and discussion

    After electro explosion, titanium surface is coated with titanium and yttrium elements. There are micro-drops, metal burrs, micro-pores and micro-cracks found on the surface. Figure 1 illustrates the surface microstructural morphology. The X-ray spectrum analysis of the coating reveals the presence of oxygen and carbon besides titanium and yttrium. This may be connected with the low vacuum condition in the processing. The microstructure and chemical constitution of the coating layer is presented in Figure 2. It reveals that the element distribution in the surface later, especially yttrium, is not uniformly.

Figure 1 Electron microscopic image for titanium surface after electro explosion.

Figure 1 Electron microscopic image for titanium surface after electro explosion.

Figure 2 The microstructure and chemical composition of the titanium surface after electro explosion alloying with yttrium powder. The frames in the images indicate the micro X-ray spectrum analysis regions.

Figure 2 The microstructure and chemical composition of the titanium surface after electro explosion alloying with yttrium powder. The frames in the images indicate the micro X-ray spectrum analysis regions.

    An analysis of the cross-sectional metallographic microstructure reveals significant non-uniform multilayers. There are 4 layers, as demonstrated in Figure 3. The top layer (designated by I in Figure 3) contains the most coarsening structure. The layer III has the most dispersed microstructure. Layer IV is in the substrate but is affected by the thermal effect in the processing.

Figure 3 The microstructures obtained from the cross section examination of the coating layer formed by electro explosion of yttrium. The labels represent the different microstructural layers. The images are in different scales.

Figure 3 The microstructures obtained from the cross section examination of the coating layer formed by electro explosion of yttrium. The labels represent the different microstructural layers. The images are in different scales.

    Application of high intensity EBT to the surface formed by electro explosion alloying causes the surface layer to melt. This treatment smoothens out the surface and eliminates micro-pores. However, the micro-cracks remain.  The microstructure of the surface after EBT treatment is demonstrated in Figure 4. Different structures can be detected from the electron microscope image. By the micro X-ray spectrum analysis, it can be found that the chemical composition of the matrix shown in Fig.4 is mainly yttrium-enriched phase. The large islands with 10-40 mm in dimension are the titanium-enriched phase. There are also some globular inclusions with dimensions between 100 and 300 nm. Table 1 shows the chemical constitutions.

Figure 4 a-The SEM image reveals the microstructure of surface layer after EBT; b and c present the micro X-ray diffraction spectrums in the frames indicated in (a).

Figure 4 a-The SEM image reveals the microstructure of surface layer after EBT; b and c present the micro X-ray diffraction spectrums in the frames indicated in (a).

    Figure 5 shows that the globular inclusions are located in an orderly fashion outlining the titanium regions. The titanium-enriched region is in grains with dimension between 0.5 and 1.5 mm. The region is form by eutectic transformation. The equilibrium predicts the eutectic composition of 30 at.% yttrium. It has been reported the possibility of form such eutectic microstructure at 18 at.% yttrium [19-21]. In table 1, 18 wt.% yttrium corresponds to 26.7 wt.% yttrium if C and O are excluded. This is equivalent to 18 at.% yttrium.

Table 1 Chemical compositions (weight %) in the areas indicated in Figure 4

table1

Figure 5 SEM image for titanium-enriched region treated after a-by the EBT, b-by the EEA.

Figure 5 SEM image for titanium-enriched region treated after a-by the EBT, b-by the EEA.

    In the adjacent region between Ti-rich islands and Y-rich matrix the microstructure is lamellar type. Figure 6 demonstrates it with more details. The inter-lamellar space is between 200-300 nm. The micro X-ray diffraction spectrum analysis reveals 85 at.% yttrium and 15 at.% titanium. It should be pointed out that at the equilibrium phase diagram predicted a eutectic composition with 80 at.% yttrium [1].

Figure 6 Lamellar eutectic formed in the adjacent region between Ti-rich and Y-rich zones.

Figure 6 Lamellar eutectic formed in the adjacent region between Ti-rich and Y-rich zones.

    EBT-induced surface melting affected not only the coating layer formed by EEA but a total 30 to 40 mm thick dispersion layer in the materials. A surface layer of 10-15 mm thickness is modified most significantly. This is demonstrated in Figure 7.

Figure 7 The microstructure in the cross-section of the material. The transition layer separating layers III and IV designated in Fig. 3 is the presented in (d).

Figure 7 The microstructure in the cross-section of the material. The transition layer separating layers III and IV designated in Fig. 3 is the presented in (d).

    The properties of the modified surface layer by the combination of EEA and EBT have been tested and the results are compared with that without EEA and EBT treatments. It has been found that the micro-hardness of the surface layer is increased by 3 times, the friction coefficient of the surface decreases by more than 3 times, and the wear rate is reduced by more than 4 times.

Conclusions

    A titanium-yttrium surface layer has been formed by electro explosion alloying and electron-beam treatment. The investigations to the microstructure, chemical and phase compositions, mechanical and tribological properties of the alloyed layer have been carried out. It has been shown that electro explosion alloying of titanium and yttrium is accompanied with the saturation of a surface layer oxygen and carbon, which lead to the formation of oxides and carbides of titanium and yttrium. The subsequent irradiation using electron beam is accompanied with the structure dispersion to nano and submicron scales, and the decrease of oxygen and carbon concentration in the surface layer. The formation of two types of eutectic has been revealed. It has been shown that the titanium-enriched eutectic structure has a globular shape and the yttrium-enriched eutectic has a lamellar structure. It has been established that the formation of the surface layer enriched by yttrium, carbides and oxides of titanium and yttrium enables significant increment of materials micro-hardness, reduction of surface friction coefficient and enhancement of wear resistance.

References

1. A.E. Vol, Structure and Properties of Binary Metallic Systems, Moscow: Gosfizmatlitizdat, vol. 2 1962).

2. B.I. Shapoval, B.M. Azhazha, B.M. Arzhavin, I.B. Dolya, et al., Some physico-mechanical properties of microcomposite Cu-Fe. Problems of atomic science and technology 1, 133-135 (2002).

3. M.A. Tikhonovsky, Investigation of directed phase transformations and development of microcomposite materials in research center of Rharkov Institute of Physics and Technology. Problems of atomic science and technology 6, 115 -127 (2004).

4. M.A. Tikhonovsky, V.T. Petrenko, V.S. Bezrodny, Structure imperfection and strength of highly deformed microcomposites (Leningrad: “Science, Mechanism of damage and strength of heterogeneous materials” 193p 1985).

5. Yu.F. Ivanov, S.V. Karpii, M.M. Morozov, V.E. Gromov, et al., Structure, phase composition and properties of titanium after electroexplosion alloying and electron-beam treatment (Novokuznetsk: Publishing house SibSIU 173p 2010).

6. V.E. Gromov, Formation of structural phase states of metals and alloys in electroexplosion alloying and electron-beam treatment (Novokuznetsk: Publishing house SibSIU 211p 2011).

7. J.C. Walker, J. W. Murray, M. Nie, et al., The effect of large-area pulsed electron beam melting on the corrosion and microstructure of a Ti6Al4V alloy. Applied surface science 311, 534-540 (2014).

8. Y.K. Gao, Surface modification of TC4 titanium alloy by high current pulsed electron beam (HCPEB) with different pulsed energy densities. Journal of Alloys and Compounds 572, 180-185 (2013).

9. X.D. Zhang, J. X. Zou, S. Weber, et al., Microstructure and property modifications in a near alpha Ti alloy induced by pulsed electron beam surface treatment. Surface & Coatings Technology 206, 295-304 (2011).

10. X.D. Zhang, S.Z. Hao, X.N. Li, et al., Surface modification of pure titanium by pulsed electron beam. Applied Surface Science 257, 5899-5902 (2011). 

11. V. Rotshtein, Yu.F. Ivanov, A. Markov, Surface treatment of materials with low-energy, high-current electron beams (Materials surface processing by directed energy techniques) (London: Elsevier, chapter 6 205p 2006).

12. Yu.F. Ivanov, V.E. Gromov, V.A. Grishunin, et al., Structure of surface layer and fatigue life of rail steel irradiated with high intensity electron beam. Physical mesomechanics 16, 47-52 (2013).

13. Yu.F. Ivanov, V.E. Gromov, V.V. Sizov, et al., Evolution of structure and phase composition of stainless steel 20Cr23N18 at cyclic deformation. Materialovedenie 4, 34-39 (2013).

14. Yu.F. Ivanov, N.N. Koval, S.V. Gorbunov, et al., Multicycle fatigue of stainless steel treated with high intensity electron beam: surface layer structure. Russian Physics Journal 54, 575 – 583 (2011). doi:10.1007/s11182-011-9654-8

15. Yu.F. Ivanov, D.A. Bessonov, S.V. Vorobiev, et al., Fatigue life of martensite class steel modified with high intensity electron beams (Novokuznetsk: “Inter-Kuzbass”, 259p 2011).

16. V.E. Gromov, Yu.F. Ivanov, V.A. Grishunin, et al., Scale levels of structural phase states and fatigue life of rail steel after electron-beam treatment. Uspehi Fiziki Metallov 14, 67- 83 (2013). 

17. Yu.F. Ivanov, K.V. Alsaraeva, V.E. Gromov, et al., Increase of fatigue life of silumin in treatment with high intensity pulse electron beam. Fundamental’nye problemy sovremennogo materialovedenia» («Basic Problems of Material Science» (BPMS)) 11, 281 - 284 (2014). 

18. Titanium alloys. Metallography of titanium alloys (M.: Metallurgy 464p 1980).

19. A.Ya. Bagautdinov, E.A. Budovskikh, Yu.F. Ivanov, V.E. Gromov, Physical foundations of electroexplosion alloying of metals and alloys (Novokuznetsk: Publishing house SibSIU 301p 2007).

20. L. Engle, G. Klingele, Scanning electron microscopy. Fracture: Reference book. Transl. from German (M.: Metallurgy 232p 1986).

21. W.P. Gong, T.F. Chen, D.J. Li, Y. Liu, Thermodynamic investigation of Fe-Ti-Y ternary system. Trans. Nonferrous Met. Soc. China 19, 199-204 (2009).

 

Acknowledgements

    This work was financially supported by projects RFFI 3 № 13-08-98084_r-a-siberia, № 13-02-12009 ofi-m and Ministry of Education and Science № 2708 and № 3.1496.2014/K of Russian.

References

1. A.E. Vol, Structure and Properties of Binary Metallic Systems, Moscow: Gosfizmatlitizdat, vol. 2 1962).
2. B.I. Shapoval, B.M. Azhazha, B.M. Arzhavin, I.B. Dolya, et al., Some physico-mechanical properties of microcomposite Cu-Fe. Problems of atomic science and technology 1, 133-135 (2002).
3. M.A. Tikhonovsky, Investigation of directed phase transformations and development of microcomposite materials in research center of Rharkov Institute of Physics and Technology. Problems of atomic science and technology 6, 115 -127 (2004).
4. M.A. Tikhonovsky, V.T. Petrenko, V.S. Bezrodny, Structure imperfection and strength of highly deformed microcomposites (Leningrad: “Science, Mechanism of damage and strength of heterogeneous materials” 193p 1985).
5. Yu.F. Ivanov, S.V. Karpii, M.M. Morozov, V.E. Gromov, et al., Structure, phase composition and properties of titanium after electroexplosion alloying and electron-beam treatment (Novokuznetsk: Publishing house SibSIU 173p 2010).
6. V.E. Gromov, Formation of structural phase states of metals and alloys in electroexplosion alloying and electron-beam treatment (Novokuznetsk: Publishing house SibSIU 211p 2011).
7. J.C. Walker, J. W. Murray, M. Nie, et al., The effect of large-area pulsed electron beam melting on the corrosion and microstructure of a Ti6Al4V alloy. Applied surface science 311, 534-540 (2014).
8. Y.K. Gao, Surface modification of TC4 titanium alloy by high current pulsed electron beam (HCPEB) with different pulsed energy densities. Journal of Alloys and Compounds 572, 180-185 (2013).
9. X.D. Zhang, J. X. Zou, S. Weber, et al., Microstructure and property modifications in a near alpha Ti alloy induced by pulsed electron beam surface treatment. Surface & Coatings Technology 206, 295-304 (2011).
10. X.D. Zhang, S.Z. Hao, X.N. Li, et al., Surface modification of pure titanium by pulsed electron beam. Applied Surface Science 257, 5899-5902 (2011). 
11. V. Rotshtein, Yu.F. Ivanov, A. Markov, Surface treatment of materials with low-energy, high-current electron beams (Materials surface processing by directed energy techniques) (London: Elsevier, chapter 6 205p 2006).
12. Yu.F. Ivanov, V.E. Gromov, V.A. Grishunin, et al., Structure of surface layer and fatigue life of rail steel irradiated with high intensity electron beam. Physical mesomechanics 16, 47-52 (2013).
13. Yu.F. Ivanov, V.E. Gromov, V.V. Sizov, et al., Evolution of structure and phase composition of stainless steel 20Cr23N18 at cyclic deformation. Materialovedenie 4, 34-39 (2013).
14. Yu.F. Ivanov, N.N. Koval, S.V. Gorbunov, et al., Multicycle fatigue of stainless steel treated with high intensity electron beam: surface layer structure. Russian Physics Journal 54, 575 – 583 (2011). doi:10.1007/s11182-011-9654-8
15. Yu.F. Ivanov, D.A. Bessonov, S.V. Vorobiev, et al., Fatigue life of martensite class steel modified with high intensity electron beams (Novokuznetsk: “Inter-Kuzbass”, 259p 2011).
16. V.E. Gromov, Yu.F. Ivanov, V.A. Grishunin, et al., Scale levels of structural phase states and fatigue life of rail steel after electron-beam treatment. Uspehi Fiziki Metallov 14, 67- 83 (2013). 
17. Yu.F. Ivanov, K.V. Alsaraeva, V.E. Gromov, et al., Increase of fatigue life of silumin in treatment with high intensity pulse electron beam. Fundamental’nye problemy sovremennogo materialovedenia» («Basic Problems of Material Science» (BPMS)) 11, 281 - 284 (2014). 
18. Titanium alloys. Metallography of titanium alloys (M.: Metallurgy 464p 1980).
19. A.Ya. Bagautdinov, E.A. Budovskikh, Yu.F. Ivanov, V.E. Gromov, Physical foundations of electroexplosion alloying of metals and alloys (Novokuznetsk: Publishing house SibSIU 301p 2007).
20. L. Engle, G. Klingele, Scanning electron microscopy. Fracture: Reference book. Transl. from German (M.: Metallurgy 232p 1986).
21. W.P. Gong, T.F. Chen, D.J. Li, Y. Liu, Thermodynamic investigation of Fe-Ti-Y ternary system. Trans. Nonferrous Met. Soc. China 19, 199-204 (2009).

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Additional Info

  • Type of Publishing: JOUR - Journal
  • Title:

    Structure phase states formation of Ti-Y surface layer by electro explosion and electron-beam treatment

  • Author: V.E. Gromov, K.V. Sosnin, Yu.F. Ivanov, X.L. Wang, M.S. Liu, Y. Wu, E.S. Ivanova, S.A. Nevskii
  • Year: 2015
  • Volume: 2
  • Issue: 3
  • Journal Name: Materials and Electronics Engineering
  • Publisher: Nicety Press Company Limited
  • ISSN: 2410-1648
  • URL: http://www.meej.org/volume-2/october-2015/item/373-structure-phase-states-formation-of-ti-y-surface-layer-by-electro-explosion-and-electron-beam-treatment
  • Abstract:

    A titanium-yttrium composite surface layer is formed on pure titanium surface by electro explosion and electron-beam treatments. The composite consists of titanium-rich and yttrium-rich eutectic microstructures. Both eutectics are in non-equilibrium state with their chemical constitution deviation from that in equilibrium phase diagram. The surface layer increases the surface hardness by three times, decreases the friction coefficient by 3 times and reduces the ware rate by 4 times in comparison with that of the surface of pure titanium.

  • Publish Date: Thursday, 08 October 2015
  • Start Page: 3
  • DOI: 10.11605/mee-2-3