- Email: [email protected]
The isothermal section of the Ti–Co–Zr ternary system at 773 K
Journal of Alloys and Compounds 482 (2009) 127–130
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom
The isothermal section of the Ti–Co–Zr ternary system at 773 K Jichao Jiang, Yongzhong Zhan ∗ , Zan Sun, Dan Peng, Guanghua Zhang Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004, PR China
a r t i c l e
i n f o
Article history: Received 26 November 2008 Received in revised form 17 April 2009 Accepted 17 April 2009 Available online 23 April 2009 Keywords: Metals and alloys Phase diagrams X-ray diffraction Scanning electron microscopy (SEM)
a b s t r a c t The phase equilibria of the Ti–Co–Zr ternary system at 773 K have been investigated mainly by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive analysis (EDX). The isothermal section consists of 16 single-phase regions, 31 two-phase regions and 16 three-phase regions. There are 11 binary compounds, i.e. CoZr3 , CoZr2 , CoZr, Co2 Zr, Co23 Zr6 , Co11 Zr2 , TiCo3 , h-TiCo2 , c-TiCo2 , TiCo, Ti2 Co in the system. The existence of two ternary compounds Co10 Ti7 Zr3 and Co66 Ti17 Zr17 has been confirmed at 773 K. Co2 Zr, CoZr3 and TiCo have a range of homogeneity. The solubilities of Ti in CoZr was determined to be up to 8.1 at.% Ti. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Titanium and cobalt are basic elements of many commercial and industrial alloys used for high-temperature, high performance, and in case of Ti, light-weight applications. In addition, due to its excellent biocompatibility, high corrosion resistance and low density, titanium and its alloys are widely used for dental and orthopedic implant applications. Zr and Co are among the more important alloying elements in structural high-temperature Ti-alloys. Cobalt has also been used in implant alloys in dentistry and medicine for many years [1]. Intermetallic compounds of Co–Ti system are of interest for their excellent mechanical strength, high hardness at elevated temperatures, high melting point, good oxidization and corrosion resistance and good phase stability [2]. Zirconium–tin alloys are of practical importance for nuclear industry. Partial substitution of Zr for Ti might give possibilities to control the properties of Zr alloys, particularly to decrease the weight of the parts of nuclear reactors. As a result, it is important to investigate the phase relationships of the Ti–Co–Zr ternary system. In Refs. [3,4], the Zr–Ti phase diagrams without compound was reported. A phase diagram of the Co–Zr binary system with six compounds was reported [5], which are Co11 Zr2 , Co23 Zr6 (Co4 Zr), Co2 Zr, CoZr, CoZr2 and CoZr3 . Among these, Co2 Zr and CoZr3 have a range of homogeneity. It is found that the Co2 Zr, CoZr, and CoZr2 phases melt congruently. The Co23 Zr6 and Co11 Zr2 phases form through peritectic reactions L + Co2 Zr ↔ Co23 Zr6 at 1452 ◦ C and L + Co23 Zr6 ↔ Co11 Zr2 at 1272 ◦ C. Four eutectic reactions, L ↔ (␥Co) + Co11 Zr2 , L ↔ Co2 Zr + CoZr, L ↔ CoZr + CoZr2
∗ Corresponding author. Tel.: +86 771 3272311; fax: +86 771 3233530. E-mail address: [email protected] (Y. Zhan). 0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2009.04.069
and L ↔ CoZr2 + (Zr), occur at 1232 ◦ C, 1312 ◦ C, 1061 ◦ C, and 981 ◦ C, respectively. A eutectoid reaction, (Zr) ↔ CoZr2 + (␣Zr), occurs at 834 ◦ C. At the Co-rich end, a eutectoid reaction (␥Co) ↔ Co11 Zr2 + (Co), occurs near 422 ◦ C. In the Co–Ti system, five intermetallic compounds, TiCo3 , h-TiCo2 , c-TiCo2 , TiCo and Ti2 Co occur besides the terminal solution phases i.e. ␣Ti, Ti, ␣Co and Co [6]. There are conflicting reports about the two variants of the Laves phase TiCo2 . References. [7,8] found only h-TiCo2 to be stable, however Ref. [9] found only c-TiCo2 to be stable. Many other groups found both variants [10–15]. The (␣Co) solid solution undergoes an allotropic martensitic transformation to form (Co) after cooling [16]. In Ref. [6], Two eutectic reactions, L ↔ (Ti) + Ti2 Co at 1020 ◦ C and L ↔ (h-TiCo2 ) + TiCo3 at 1170 ◦ C. Four peritectic reactions, L+ TiCo ↔ Ti2 Co, L + TiCo ↔ (c-TiCo2 ), L + (c-TiCo2 ) ↔ (hTiCo2 ), L + Co ↔ TiCo3 occur at 1058 ◦ C, 1235 ◦ C, 1210 ◦ C, and 1190 ◦ C, respectively. Eutectoid reaction (Ti) ↔ (␣Ti) + Ti2 Co occurs at 685 ◦ C. To our knowledge, two ternary compounds Co10 Ti7 Zr3 and Co66 Ti17 Zr17 in the Ti–Co–Zr systems are present [17]. The structural data for the intermetallic compounds in the Ti–Co–Zr systems are given in Table 1. Up to now, the phase diagram of the Ti–Co–Zr ternary system has not yet been reported. The purpose of the present work is to investigate experimentally the phase equilibria of Ti–Co–Zr system, mainly by the construction of an isothermal section at 773 K, so as to provide essential information for the design and fabrication of new-type polynary titanium or zirconium alloys. 2. Experimental methods The purities of zirconium, titanium, cobalt used in the work were all 99.99 wt.%. All samples weighing 2 g were prepared in an arc furnace and melted three times in an atmosphere of puri-
128
J. Jiang et al. / Journal of Alloys and Compounds 482 (2009) 127–130
Table 1 The structural data for the intermetallic compounds in the Ti–Co–Zr systems. Compound
Space group
Structure type
Ti2 Co TiCo2 (h) TiCo2 (c) TiCo TiCo3 Co23 Zr6 CoZr CoZr2 CoZr3 Co2 Zr Co66 Ti17 Zr17 Co10 Ti7 Zr3
¯ Fd3m P63/mmc ¯ Fd3m ¯ Pm3m ¯ Pm3m ¯ Fm3m ¯ Pm3m
Ti2 Ni MgNi2 Cu2 Mg ClCs AuCu3 Mn23 Th6 ClCs Al2 Cu BRe3 Cu2 Mg Cu2 Mg ClCs
I4/mcm Cmcm ¯ Fd3m ¯ Fd3m ¯ Pm3m
Lattice parameters (nm)
Reference
a
b
c
1.129 0.47333 0.6692 0.3002 0.3614 1.151 0.3181 0.6363 0.327 0.6951 0.6798 0.3060
– – – – – – – – 1.084 – – –
– 1.541 – – – – – 0.5469 0.895 – – –
[18] [18] [18] [18] [18] [19] [19] [19] [19] [19] [17] [17]
fied argon, then they were sealed in evacuated quartz tubes for homogenization annealing. The melted alloys were sealed in an evacuated quartz tube containing titanium chips as an oxygen getter. The tube was placed in a resistance furnace for homogenization treatment and then annealed at different temperatures in order to attain good homogenization. The heat treatment temperature of the alloys was determined by differential thermal analysis (DTA) results of some typical ternary alloys or based on previous work of the three binary phase diagrams. The alloys were homogenized at 1173 K for 480 h at first and then cooled down to 773 K for 240 h. Finally, all these annealed alloys were quenched in liquid nitrogen. X-ray powder diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive analysis (EDX) were used in the present investigation. Most homogenized alloy powders or buttons were investigated by X-ray diffraction, which was carried out on a Rigaku D/Max 2500 V diffractometer (CuK␣ monochromator) using JADE 5.0 software with analyzed angle ranging from 2 = 30–80◦ at a voltage of 40 kV, and a current of 200 mA.
3. Results and discussion 3.1. Binary system The present work has indicated that no binary compound exists in the Zr–Ti system, which agrees well with the results of Refs. [3,4]. A phase diagram of the Co–Zr binary system with six compounds was reported [5]. The present work confirms the existence of six binary compounds i.e. CoZr3 , CoZr2 , CoZr, Co2 Zr, Co23 Zr6 and Co11 Zr2 , in the Co–Zr binary system at 773 K. For the Ti–Co system, the previous binary phase diagram [6] shows 6 intermediate phases, they are TiCo3 , h-TiCo2 , c-TiCo2 , TiCo and Ti2 Co. By analyzing the XRD results, it is confirmed in this work that these binary compounds all exist at 773 K.
Fig. 1. The XRD pattern (a) and the SEM micrograph (b) of the equilibrated alloy containing 34 at.% Ti, 62 at.% Co and 4 at.% Zr.
3.2. Ternary phases The existence of ternary compounds Co10 Ti7 Zr3 and Co66 Ti17 Zr17 that reported in Ref. [17] can be confirmed in the 2 three-phase regions c-TiCo2 + TiCo + Co66 Ti17 Zr17 and Co2 Zr + TiCo + Co10 Ti7 Zr3 in this work. The equilibrated samples containing 34 at.% Ti, 62 at.% Co and 4 at.% Zr consists of c-TiCo2 , TiCo and Co66 Ti17 Zr17 , as shown in the XRD pattern of Fig. 1(a). As examined through SEM and EDX (illustrated in Fig. 1(b)), the three-phases can be clearly observed. For the equilibrated samples containing 32 at.% Ti, 54 at.% Co and 14 at.% Zr, the XRD pattern (shown in Fig. 2) clearly indicates the existence of three-phases, i.e. Co2 Zr, TiCo and Co10 Ti7 Zr3 .
Fig. 2. The XRD pattern of the equilibrated sample containing 32 at.% Ti, 54 at.% Co and 14 at.% Zr.
J. Jiang et al. / Journal of Alloys and Compounds 482 (2009) 127–130
129
Fig. 3. The experimental isothermal section of the Ti–Co–Zr ternary system at 773 K.
3.3. Isothermal section Based on the results of XRD, SEM and EDX, the phase relationships of the ternary Ti–Co–Zr system at 773 K was determined and it is shown in Fig. 3. This isothermal section consists of 16 singlephase regions, 31 two-phase regions, and 16 three-phase regions. Details of the three-phase regions and compositions of the typical alloys are given in Table 2. Fig. 4(a) illustrates the XRD pattern of the equilibrated samples containing 6 at.% Ti, 72 at.% Co and 22 at.% Zr. It is obvious that there are three-phases Co2 Zr, Co23 Zr6 and Co66 Ti17 Zr17 . Another equilibrated sample containing 60 at.% Ti, 26 at.% Co and 14 at.% Zr consists of three-phases Ti, Ti2 Co and CoZr2 , as indicated in the XRD pattern of Fig. 4(b). As a result, the 2 three-phase regions Co2 Zr + Co23 Zr6 + Co66 Ti17 Zr17 and Ti + Ti2 Co + CoZr3 can be confirmed in this system. The solid solubility ranges of all single-phases in this isothermal section were determined by X-ray diffraction using the phasedisappearing method and comparing the shift of the XRD pattern of the samples near the compositions of the binary phases and the ternary phases. The results showed that Co2 Zr, CoZr3 and TiCo have a range of homogeneity, i.e. 5.7 at.%, 7.1 at.% and 5.1 at.% for them, Table 2 Details of the three-phase regions and compositions of the typical alloys in the Ti–Co–Zr system at 773 K. Phase regions
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Alloy composition (at.%) Ti
Co
Zr
40 60 26 40 50 16 12 32 22 34 26 28 6 4 6 16
10 26 30 40 46 46 56 54 62 62 70 67 72 78 82 78
50 14 44 20 4 38 32 14 16 4 4 5 22 18 12 6
Phase composition
Ti + Zr + CoZr3 Ti + Ti2 Co + CoZr3 CoZr2 + Ti2 Co + CoZr3 CoZr2 + Ti2 Co + Co10 Ti7 Zr3 Ti2 Co + Co10 Ti7 Zr3 + TiCo CoZr2 + CoZr + Co10 Ti7 Zr3 Co2 Zr + CoZr + Co10 Ti7 Zr3 Co2 Zr + TiCo + Co10 Ti7 Zr3 Co2 Zr + TiCo + Co66 Ti17 Zr17 c-TiCo2 + TiCo + Co66 Ti17 Zr17 h-TiCo2 + TiCo3 + Co66 Ti17 Zr17 Co66 Ti17 Zr17 + c-TiCo2 +h-TiCo2 Co2 Zr + Co23 Zr6 + Co66 Ti17 Zr17 Co11 Zr2 + Co23 Zr6 + Co66 Ti17 Zr17 Co11 Zr2 + Co + Co66 Ti17 Zr17 TiCo3 + Co + Co66 Ti17 Zr17
Fig. 4. The XRD pattern of two equilibrated samples of Ti–Co–Zr ternary system: (a) Ti 6 at.%, Co 72 at.% and Zr 22 at.%; (b) Ti 60 at.%, Co 26 at.% and Zr 14 at.%.
respectively. The solubilitie of Ti in CoZr was determined to be up to 8.1 at.% Ti. None of the other phase found in this system has a remarkable homogeneity range at 773 K. 4. Conclusion The phase relationships of the Ti–Co–Zr ternary system at 773 K have been determined experimentally for the first time. The following three-phase equilibria were observed: Ti + Zr + CoZr3 , Ti + Ti2 Co + CoZr3 , CoZr2 + Ti2 Co + CoZr3 , CoZr2 + Ti2 Co + Co10 Ti7 Zr3 , Ti2 Co + Co10 Ti7 Zr3 + TiCo, CoZr2 + CoZr + Co10 Ti7 Zr3 , Co2 Zr + CoZr + Co10 Ti7 Zr3 , Co2 Zr + TiCo + Co10 Ti7 Zr3 , Co2 Zr + TiCo + Co66 Ti17 Zr17 , cTiCo2 + TiCo + Co66 Ti17 Zr17 , h-TiCo2 + TiCo3 + Co66 Ti17 Zr17 , Co66 Ti17 Zr17 + c-TiCo2 + h-TiCo2 , Co2 Zr + Co23 Zr6 + Co66 Ti17 Zr17 , Co11 Zr2 + Co23 Zr6 + Co66 Ti17 Zr17 , Co11 Zr2 + Co + Co66 Ti17 Zr17 , TiCo3 + Co + Co66 Ti17 Zr17 . The ternary compounds Co10 Ti7 Zr3 and Co66 Ti17 Zr17 are found in the ternary system at 773 K. The solubility of Ti in CoZr was determined to be up to 8.1 at.% Ti. Acknowledgements The authors wish to express thanks to the financial support from the National Natural Science Foundation of China (50761003, 50601006), the Key Project of China Ministry of Education (207085) and the Opening Foundation of State Key Laboratory of Powder Metallurgy (2008). References [1] L. Slokar, T. Matakovic, P. Matakovic, Metalurgija 43 (2004) 273–277. [2] C.L. Yeh, C.C. Yeh, J. Alloys Compd. 396 (2005) 228–232. [3] T.B. Massalski (Ed.), Binary Alloy Phase Diagrams, ASM International, 2nd ed., Metals Park, OH, 1990. [4] V.A. Saltykov, K.A. Meleshevich, A.V. Samelyuk, O.M. Verbytska, M.V. Bulanova, J. Alloys Compd. 495 (2008) 348–353. [5] S.K. Bataleva, V.V. Kuprina, V.V. Burnasheva, V.Y. Markiv, G.N. Ronami, S.M. Kurnetsova, Vestn. Mosk. Univ. Khim. 5 (1970) 557–611.
130
J. Jiang et al. / Journal of Alloys and Compounds 482 (2009) 127–130
[6] J.L. Murray, in: J.L. Murray (Ed.), Phase Diagram of Binary Titanium Alloys, ASM International, Materials Park, OH, 1987, pp. 59–68. [7] P. Duwez, J.L. Taylor, Trans. AIME 188 (1950) 1173. [8] R.W. Fountain, W.D. Forgeng, Trans. AIME 215 (1959) 98. [9] B. Uhrenius, K. Forsen, Z. Metallkd. 74 (1983) 610. [10] H.J. Wallbaum, Arch. Eisenhuttenwes 10 (1941) 521 (in German). [11] A.E. Dwight, Trans. AIME 215 (1959) 283. [12] T. Nakamichi, J. Phys. Soc. Jpn. 25 (1968) 1189. [13] T. Nakamichi, Y. Aoki, M. Yamamoto, J. Phys. Soc. Jpn. 28 (1970) 590.
[14] V.V. Pet’kov, M.V. Kireev, Metallofizika 33 (1971) 107 (in Russian). [15] P.J. Van der Straten, G.F. Basten, F.J. Van Loo, G.D. Rieck, Z. Metallkd. 67 (1976) 152. [16] W. Betteridge, Prog. Mater. Sci. 24 (1979) 51. [17] Z. Blazina, R. Trojko, J. Less-Common Met. 133 (1987) 277–286. [18] P. Villars, Pearson’s Handbook of Crystallographic Data, ASM International, Materials Park, OH, 1997, p. 1379–1380. [19] P. Villars, Pearson’s Handbook of Crystallographic Data, ASM International, Materials Park, OH, 1997, pp.1385.
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom
The isothermal section of the Ti–Co–Zr ternary system at 773 K Jichao Jiang, Yongzhong Zhan ∗ , Zan Sun, Dan Peng, Guanghua Zhang Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004, PR China
a r t i c l e
i n f o
Article history: Received 26 November 2008 Received in revised form 17 April 2009 Accepted 17 April 2009 Available online 23 April 2009 Keywords: Metals and alloys Phase diagrams X-ray diffraction Scanning electron microscopy (SEM)
a b s t r a c t The phase equilibria of the Ti–Co–Zr ternary system at 773 K have been investigated mainly by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive analysis (EDX). The isothermal section consists of 16 single-phase regions, 31 two-phase regions and 16 three-phase regions. There are 11 binary compounds, i.e. CoZr3 , CoZr2 , CoZr, Co2 Zr, Co23 Zr6 , Co11 Zr2 , TiCo3 , h-TiCo2 , c-TiCo2 , TiCo, Ti2 Co in the system. The existence of two ternary compounds Co10 Ti7 Zr3 and Co66 Ti17 Zr17 has been confirmed at 773 K. Co2 Zr, CoZr3 and TiCo have a range of homogeneity. The solubilities of Ti in CoZr was determined to be up to 8.1 at.% Ti. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Titanium and cobalt are basic elements of many commercial and industrial alloys used for high-temperature, high performance, and in case of Ti, light-weight applications. In addition, due to its excellent biocompatibility, high corrosion resistance and low density, titanium and its alloys are widely used for dental and orthopedic implant applications. Zr and Co are among the more important alloying elements in structural high-temperature Ti-alloys. Cobalt has also been used in implant alloys in dentistry and medicine for many years [1]. Intermetallic compounds of Co–Ti system are of interest for their excellent mechanical strength, high hardness at elevated temperatures, high melting point, good oxidization and corrosion resistance and good phase stability [2]. Zirconium–tin alloys are of practical importance for nuclear industry. Partial substitution of Zr for Ti might give possibilities to control the properties of Zr alloys, particularly to decrease the weight of the parts of nuclear reactors. As a result, it is important to investigate the phase relationships of the Ti–Co–Zr ternary system. In Refs. [3,4], the Zr–Ti phase diagrams without compound was reported. A phase diagram of the Co–Zr binary system with six compounds was reported [5], which are Co11 Zr2 , Co23 Zr6 (Co4 Zr), Co2 Zr, CoZr, CoZr2 and CoZr3 . Among these, Co2 Zr and CoZr3 have a range of homogeneity. It is found that the Co2 Zr, CoZr, and CoZr2 phases melt congruently. The Co23 Zr6 and Co11 Zr2 phases form through peritectic reactions L + Co2 Zr ↔ Co23 Zr6 at 1452 ◦ C and L + Co23 Zr6 ↔ Co11 Zr2 at 1272 ◦ C. Four eutectic reactions, L ↔ (␥Co) + Co11 Zr2 , L ↔ Co2 Zr + CoZr, L ↔ CoZr + CoZr2
∗ Corresponding author. Tel.: +86 771 3272311; fax: +86 771 3233530. E-mail address: [email protected] (Y. Zhan). 0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2009.04.069
and L ↔ CoZr2 + (Zr), occur at 1232 ◦ C, 1312 ◦ C, 1061 ◦ C, and 981 ◦ C, respectively. A eutectoid reaction, (Zr) ↔ CoZr2 + (␣Zr), occurs at 834 ◦ C. At the Co-rich end, a eutectoid reaction (␥Co) ↔ Co11 Zr2 + (Co), occurs near 422 ◦ C. In the Co–Ti system, five intermetallic compounds, TiCo3 , h-TiCo2 , c-TiCo2 , TiCo and Ti2 Co occur besides the terminal solution phases i.e. ␣Ti, Ti, ␣Co and Co [6]. There are conflicting reports about the two variants of the Laves phase TiCo2 . References. [7,8] found only h-TiCo2 to be stable, however Ref. [9] found only c-TiCo2 to be stable. Many other groups found both variants [10–15]. The (␣Co) solid solution undergoes an allotropic martensitic transformation to form (Co) after cooling [16]. In Ref. [6], Two eutectic reactions, L ↔ (Ti) + Ti2 Co at 1020 ◦ C and L ↔ (h-TiCo2 ) + TiCo3 at 1170 ◦ C. Four peritectic reactions, L+ TiCo ↔ Ti2 Co, L + TiCo ↔ (c-TiCo2 ), L + (c-TiCo2 ) ↔ (hTiCo2 ), L + Co ↔ TiCo3 occur at 1058 ◦ C, 1235 ◦ C, 1210 ◦ C, and 1190 ◦ C, respectively. Eutectoid reaction (Ti) ↔ (␣Ti) + Ti2 Co occurs at 685 ◦ C. To our knowledge, two ternary compounds Co10 Ti7 Zr3 and Co66 Ti17 Zr17 in the Ti–Co–Zr systems are present [17]. The structural data for the intermetallic compounds in the Ti–Co–Zr systems are given in Table 1. Up to now, the phase diagram of the Ti–Co–Zr ternary system has not yet been reported. The purpose of the present work is to investigate experimentally the phase equilibria of Ti–Co–Zr system, mainly by the construction of an isothermal section at 773 K, so as to provide essential information for the design and fabrication of new-type polynary titanium or zirconium alloys. 2. Experimental methods The purities of zirconium, titanium, cobalt used in the work were all 99.99 wt.%. All samples weighing 2 g were prepared in an arc furnace and melted three times in an atmosphere of puri-
128
J. Jiang et al. / Journal of Alloys and Compounds 482 (2009) 127–130
Table 1 The structural data for the intermetallic compounds in the Ti–Co–Zr systems. Compound
Space group
Structure type
Ti2 Co TiCo2 (h) TiCo2 (c) TiCo TiCo3 Co23 Zr6 CoZr CoZr2 CoZr3 Co2 Zr Co66 Ti17 Zr17 Co10 Ti7 Zr3
¯ Fd3m P63/mmc ¯ Fd3m ¯ Pm3m ¯ Pm3m ¯ Fm3m ¯ Pm3m
Ti2 Ni MgNi2 Cu2 Mg ClCs AuCu3 Mn23 Th6 ClCs Al2 Cu BRe3 Cu2 Mg Cu2 Mg ClCs
I4/mcm Cmcm ¯ Fd3m ¯ Fd3m ¯ Pm3m
Lattice parameters (nm)
Reference
a
b
c
1.129 0.47333 0.6692 0.3002 0.3614 1.151 0.3181 0.6363 0.327 0.6951 0.6798 0.3060
– – – – – – – – 1.084 – – –
– 1.541 – – – – – 0.5469 0.895 – – –
[18] [18] [18] [18] [18] [19] [19] [19] [19] [19] [17] [17]
fied argon, then they were sealed in evacuated quartz tubes for homogenization annealing. The melted alloys were sealed in an evacuated quartz tube containing titanium chips as an oxygen getter. The tube was placed in a resistance furnace for homogenization treatment and then annealed at different temperatures in order to attain good homogenization. The heat treatment temperature of the alloys was determined by differential thermal analysis (DTA) results of some typical ternary alloys or based on previous work of the three binary phase diagrams. The alloys were homogenized at 1173 K for 480 h at first and then cooled down to 773 K for 240 h. Finally, all these annealed alloys were quenched in liquid nitrogen. X-ray powder diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive analysis (EDX) were used in the present investigation. Most homogenized alloy powders or buttons were investigated by X-ray diffraction, which was carried out on a Rigaku D/Max 2500 V diffractometer (CuK␣ monochromator) using JADE 5.0 software with analyzed angle ranging from 2 = 30–80◦ at a voltage of 40 kV, and a current of 200 mA.
3. Results and discussion 3.1. Binary system The present work has indicated that no binary compound exists in the Zr–Ti system, which agrees well with the results of Refs. [3,4]. A phase diagram of the Co–Zr binary system with six compounds was reported [5]. The present work confirms the existence of six binary compounds i.e. CoZr3 , CoZr2 , CoZr, Co2 Zr, Co23 Zr6 and Co11 Zr2 , in the Co–Zr binary system at 773 K. For the Ti–Co system, the previous binary phase diagram [6] shows 6 intermediate phases, they are TiCo3 , h-TiCo2 , c-TiCo2 , TiCo and Ti2 Co. By analyzing the XRD results, it is confirmed in this work that these binary compounds all exist at 773 K.
Fig. 1. The XRD pattern (a) and the SEM micrograph (b) of the equilibrated alloy containing 34 at.% Ti, 62 at.% Co and 4 at.% Zr.
3.2. Ternary phases The existence of ternary compounds Co10 Ti7 Zr3 and Co66 Ti17 Zr17 that reported in Ref. [17] can be confirmed in the 2 three-phase regions c-TiCo2 + TiCo + Co66 Ti17 Zr17 and Co2 Zr + TiCo + Co10 Ti7 Zr3 in this work. The equilibrated samples containing 34 at.% Ti, 62 at.% Co and 4 at.% Zr consists of c-TiCo2 , TiCo and Co66 Ti17 Zr17 , as shown in the XRD pattern of Fig. 1(a). As examined through SEM and EDX (illustrated in Fig. 1(b)), the three-phases can be clearly observed. For the equilibrated samples containing 32 at.% Ti, 54 at.% Co and 14 at.% Zr, the XRD pattern (shown in Fig. 2) clearly indicates the existence of three-phases, i.e. Co2 Zr, TiCo and Co10 Ti7 Zr3 .
Fig. 2. The XRD pattern of the equilibrated sample containing 32 at.% Ti, 54 at.% Co and 14 at.% Zr.
J. Jiang et al. / Journal of Alloys and Compounds 482 (2009) 127–130
129
Fig. 3. The experimental isothermal section of the Ti–Co–Zr ternary system at 773 K.
3.3. Isothermal section Based on the results of XRD, SEM and EDX, the phase relationships of the ternary Ti–Co–Zr system at 773 K was determined and it is shown in Fig. 3. This isothermal section consists of 16 singlephase regions, 31 two-phase regions, and 16 three-phase regions. Details of the three-phase regions and compositions of the typical alloys are given in Table 2. Fig. 4(a) illustrates the XRD pattern of the equilibrated samples containing 6 at.% Ti, 72 at.% Co and 22 at.% Zr. It is obvious that there are three-phases Co2 Zr, Co23 Zr6 and Co66 Ti17 Zr17 . Another equilibrated sample containing 60 at.% Ti, 26 at.% Co and 14 at.% Zr consists of three-phases Ti, Ti2 Co and CoZr2 , as indicated in the XRD pattern of Fig. 4(b). As a result, the 2 three-phase regions Co2 Zr + Co23 Zr6 + Co66 Ti17 Zr17 and Ti + Ti2 Co + CoZr3 can be confirmed in this system. The solid solubility ranges of all single-phases in this isothermal section were determined by X-ray diffraction using the phasedisappearing method and comparing the shift of the XRD pattern of the samples near the compositions of the binary phases and the ternary phases. The results showed that Co2 Zr, CoZr3 and TiCo have a range of homogeneity, i.e. 5.7 at.%, 7.1 at.% and 5.1 at.% for them, Table 2 Details of the three-phase regions and compositions of the typical alloys in the Ti–Co–Zr system at 773 K. Phase regions
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Alloy composition (at.%) Ti
Co
Zr
40 60 26 40 50 16 12 32 22 34 26 28 6 4 6 16
10 26 30 40 46 46 56 54 62 62 70 67 72 78 82 78
50 14 44 20 4 38 32 14 16 4 4 5 22 18 12 6
Phase composition
Ti + Zr + CoZr3 Ti + Ti2 Co + CoZr3 CoZr2 + Ti2 Co + CoZr3 CoZr2 + Ti2 Co + Co10 Ti7 Zr3 Ti2 Co + Co10 Ti7 Zr3 + TiCo CoZr2 + CoZr + Co10 Ti7 Zr3 Co2 Zr + CoZr + Co10 Ti7 Zr3 Co2 Zr + TiCo + Co10 Ti7 Zr3 Co2 Zr + TiCo + Co66 Ti17 Zr17 c-TiCo2 + TiCo + Co66 Ti17 Zr17 h-TiCo2 + TiCo3 + Co66 Ti17 Zr17 Co66 Ti17 Zr17 + c-TiCo2 +h-TiCo2 Co2 Zr + Co23 Zr6 + Co66 Ti17 Zr17 Co11 Zr2 + Co23 Zr6 + Co66 Ti17 Zr17 Co11 Zr2 + Co + Co66 Ti17 Zr17 TiCo3 + Co + Co66 Ti17 Zr17
Fig. 4. The XRD pattern of two equilibrated samples of Ti–Co–Zr ternary system: (a) Ti 6 at.%, Co 72 at.% and Zr 22 at.%; (b) Ti 60 at.%, Co 26 at.% and Zr 14 at.%.
respectively. The solubilitie of Ti in CoZr was determined to be up to 8.1 at.% Ti. None of the other phase found in this system has a remarkable homogeneity range at 773 K. 4. Conclusion The phase relationships of the Ti–Co–Zr ternary system at 773 K have been determined experimentally for the first time. The following three-phase equilibria were observed: Ti + Zr + CoZr3 , Ti + Ti2 Co + CoZr3 , CoZr2 + Ti2 Co + CoZr3 , CoZr2 + Ti2 Co + Co10 Ti7 Zr3 , Ti2 Co + Co10 Ti7 Zr3 + TiCo, CoZr2 + CoZr + Co10 Ti7 Zr3 , Co2 Zr + CoZr + Co10 Ti7 Zr3 , Co2 Zr + TiCo + Co10 Ti7 Zr3 , Co2 Zr + TiCo + Co66 Ti17 Zr17 , cTiCo2 + TiCo + Co66 Ti17 Zr17 , h-TiCo2 + TiCo3 + Co66 Ti17 Zr17 , Co66 Ti17 Zr17 + c-TiCo2 + h-TiCo2 , Co2 Zr + Co23 Zr6 + Co66 Ti17 Zr17 , Co11 Zr2 + Co23 Zr6 + Co66 Ti17 Zr17 , Co11 Zr2 + Co + Co66 Ti17 Zr17 , TiCo3 + Co + Co66 Ti17 Zr17 . The ternary compounds Co10 Ti7 Zr3 and Co66 Ti17 Zr17 are found in the ternary system at 773 K. The solubility of Ti in CoZr was determined to be up to 8.1 at.% Ti. Acknowledgements The authors wish to express thanks to the financial support from the National Natural Science Foundation of China (50761003, 50601006), the Key Project of China Ministry of Education (207085) and the Opening Foundation of State Key Laboratory of Powder Metallurgy (2008). References [1] L. Slokar, T. Matakovic, P. Matakovic, Metalurgija 43 (2004) 273–277. [2] C.L. Yeh, C.C. Yeh, J. Alloys Compd. 396 (2005) 228–232. [3] T.B. Massalski (Ed.), Binary Alloy Phase Diagrams, ASM International, 2nd ed., Metals Park, OH, 1990. [4] V.A. Saltykov, K.A. Meleshevich, A.V. Samelyuk, O.M. Verbytska, M.V. Bulanova, J. Alloys Compd. 495 (2008) 348–353. [5] S.K. Bataleva, V.V. Kuprina, V.V. Burnasheva, V.Y. Markiv, G.N. Ronami, S.M. Kurnetsova, Vestn. Mosk. Univ. Khim. 5 (1970) 557–611.
130
J. Jiang et al. / Journal of Alloys and Compounds 482 (2009) 127–130
[6] J.L. Murray, in: J.L. Murray (Ed.), Phase Diagram of Binary Titanium Alloys, ASM International, Materials Park, OH, 1987, pp. 59–68. [7] P. Duwez, J.L. Taylor, Trans. AIME 188 (1950) 1173. [8] R.W. Fountain, W.D. Forgeng, Trans. AIME 215 (1959) 98. [9] B. Uhrenius, K. Forsen, Z. Metallkd. 74 (1983) 610. [10] H.J. Wallbaum, Arch. Eisenhuttenwes 10 (1941) 521 (in German). [11] A.E. Dwight, Trans. AIME 215 (1959) 283. [12] T. Nakamichi, J. Phys. Soc. Jpn. 25 (1968) 1189. [13] T. Nakamichi, Y. Aoki, M. Yamamoto, J. Phys. Soc. Jpn. 28 (1970) 590.
[14] V.V. Pet’kov, M.V. Kireev, Metallofizika 33 (1971) 107 (in Russian). [15] P.J. Van der Straten, G.F. Basten, F.J. Van Loo, G.D. Rieck, Z. Metallkd. 67 (1976) 152. [16] W. Betteridge, Prog. Mater. Sci. 24 (1979) 51. [17] Z. Blazina, R. Trojko, J. Less-Common Met. 133 (1987) 277–286. [18] P. Villars, Pearson’s Handbook of Crystallographic Data, ASM International, Materials Park, OH, 1997, p. 1379–1380. [19] P. Villars, Pearson’s Handbook of Crystallographic Data, ASM International, Materials Park, OH, 1997, pp.1385.