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Preparation of Al–Mo intermetallic powders by solid–liquid reaction ball milling
Journal of Alloys and Compounds 485 (2009) L9–L11
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom
Letter
Preparation of Al–Mo intermetallic powders by solid–liquid reaction ball milling Ding Chen a,∗ , Jianguo Cai a , Jianjun Fang b , Zhenhua Chen a a b
School of Material Science and Engineering, Hunan University, Changsha 410082, PR China College of Electromechanical Engineering, North China University of Technology, Beijing 100041, PR China
a r t i c l e
i n f o
Article history: Received 21 April 2009 Received in revised form 19 May 2009 Accepted 21 May 2009 Available online 28 May 2009 Keywords: Al–Mo alloy Intermetallic compound powder Solid–liquid reaction milling Mechanochemical effect
a b s t r a c t A series of Al–Mo intermetallic compound powders like Al12 Mo, Al5 Mo, Al22 Mo5 and Al17 Mo4 were been synthesized respectively at different temperatures by solid–liquid reaction ball milling, a novel mechanochemical approach. The as-milled products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show that single phase Al5 Mo and Al17 Mo4 intermetallic compound powders with an average diameter less than 100 nm may be obtained at 953 K after milling for 6 and 24 h, respectively. Finally, this paper discusses solid–liquid reaction mechanism and phase formation regularity in the milling process. © 2009 Elsevier B.V. All rights reserved.
1. Introduction The melting point and the density of molybdenum are 2896 K and 10.22 g/cm3 , respectively, and extremely different from those of aluminum which are 933 K and 2.70 g/cm3 . Obviously, the alloying of such two incompatible elements by melting process faces considerable challenges. These obstacles may be overcome by the formation of composite material using repeated fracture and cold welding of constituent powders. Some literatures on mechanical alloying of Al–Mo alloy system have been released in the past decades. Zdujic et al. reported annealing of mechanically alloyed Al73 Mo27 powders using methanol as a lubricant agent and found that intermetallic compound is formed at 973 K and may be evolved to single phase Al8 Mo3 by subsequent annealing treatment of 1373 K [1]. Meanwhile, Their works also showed that Al12 Mo and Al5 Mo phases can be obtained by annealing the mechanically treated Al90 Mo10 powders at 748 and 973 K, respectively, and Al4 Mo phase is formed by annealing the Al80 Mo20 powders. However, no intermetallic compound but the nanocrystalline structure and amorphous phase were synthesized in their studies, even when the milling time was extended to 1000 h [2]. Monagheddu et al. found that the annealing of mechanically treated Al75 Mo25 powders actually produced icosahedral–quasicrystalline phase which is a lower order structure than Al–Mo intermetallic compound phases which were not obtained at milling time up to 57 h [3]. These lit-
∗ Corresponding author. Tel.: +86 731 8821648; fax: +86 731 8821648. E-mail address: [email protected] (D. Chen). 0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2009.05.113
eratures show it is difficult to directly prepare the intermetallic phases of Al–Mo binary alloy system using common mechanical alloying method. In general, the post-annealing process is necessary to obtain a full intermetallic compound phase powders. Recently, a novel mechanochemical approach called solid–liquid reaction ball milling has been introduced by Chen and Chen [4]. A series of single intermetallic compound powders, like Fe13 Sn, Fe11 Zn40 , FeSb, Cu3 Sn, TiAl3 , Al4 W, Al13 Cu4 Fe and Al8 Fe2 Si, have been successfully obtained by this novel approach [5–9]. The average size of these intermetallic powders is less than 100 nm. In this paper, some Al–Mo intermetallic compound powders, such as Al12 Mo, Al5 Mo, Al22 Mo5 and Al17 Mo4 , are synthesized using this approach.
2. Experiment The solid–liquid reaction milling process is conducted at selected temperature in a solid–liquid reaction milling device in which a sealed milling cylinder with a diameter of 300 mm rotates in a resistance heated furnace equipped with a thermostatic system. Both balls and milling cylinder are made of the same original material to prevent melting from contamination. Mo–Al system was investigated in this paper. Al is served as the reactant due to its lower melting point. The milling cylinder is vacuumed and then filled with pure inertial gas (argon) to avoid oxidation of metals during milling at high temperature. The total mass of reactant is 50 g. The mass ratio of balls to reactant is 14:1 and rotation speed of the cylinder is 80 rpm. The temperature of milling is higher than melting point of Al to keep it at a molten state. The experimental detail has been previously described in Ref. [5].
L10
D. Chen et al. / Journal of Alloys and Compounds 485 (2009) L9–L11 Table 1 The as-milled production of Al–Mo alloy system for solid–liquid reaction ball milling. Temperature (K)
943 993 1073
Milling (time/h) 6
12
24
Al12 Mo, Al5 Mo Al5 Mo Al5 Mo, Al22 Mo5 , Al17 Mo4
Al5 Mo (mostly), Al22 Mo5 Al5 Mo, Al17 Mo4 Al17 Mo4 (mostly), Al5 Mo
Al17 Mo4 (mostly), Al5 Mo Al17 Mo4 Al17 Mo4
X-ray diffraction (XRD) measurement was performed using a diffractometer with Cu K␣ radiation. The morphologies and microstructures of the as-synthesized samples were observed by scanning electron microscopy (SEM, JSM-6700F) and transmission electron microscopy (TEM, JEM-3010). 3. Results and discussion 3.1. X-ray diffractometry and morphology The XRD results of the Al–Mo alloy system produced by solid–liquid reaction ball milling process under various conditions are shown in Table 1. It can be concluded that Al12 Mo, Al5 Mo,
Al22 Mo5 and Al17 Mo4 intermetallic phases were synthesized with different milling time at different temperatures. For instance, single phase Al5 Mo, the mixture of Al5 Mo and Al17 Mo4 , and single phase Al17 Mo4 were obtained at 993 K by milling 6, 12 and 24 h respectively. Fig. 1 shows the XRD patterns of the as-milled products of Al–Mo system at 993 K at different milling time. The milling temperature and milling time affect the component of the as-milled products based on XRD results. Al–Mo intermetallic compound powders with a higher Mo content can be formed more easily at higher temperature and longer milling time. The typical morphology of Al–Mo intermetallic compound powders obtained by solid–liquid reaction ball milling is shown in Fig. 2. The average size of particles is less than 100 nm. 3.2. Mechanism of solid–liquid reaction ball milling
Fig. 1. XRD pattern of as-milled products of Al–Mo system at 993 K after different milling time.
As mentioned above, Al–Mo intermetallics are difficult to synthesize by common process. Generally, the metals must be heated to certain temperatures above their melting points and then cooled down for the preparation of intermetallics. However, some Al–Mo intermetallic compounds were obtained by solid–liquid reaction ball milling process at a temperature far lower than the melting point of molybdenum, indicating that its mechanism for the formation of intermetallic phases is different from the traditional mechanism. The possible mechanism is discussed as follows. Based on the principle of mechanochemistry, the continuous collisions between the milling balls and liquid during milling process can induce chemical reactions on the surface of the milling balls. The reaction product can be immediately peeled off from the ball surface and enters into liquid to form ultrafine particles. Because there are a number of fine crystals in the liquid at the same time due to fracturing effect of milling, it is not easy for agglomeration of particles in the melt. That is the reason why the ultimate product of solid–liquid reaction milling is ultrafine pow-
Fig. 2. Typical morphology of Al–Mo intermetallic compound powder (Al5 Mo) obtained by solid–liquid reaction ball milling: (a) SEM image and (b) TEM image.
D. Chen et al. / Journal of Alloys and Compounds 485 (2009) L9–L11
L11
lic phases are only observed in few alloy systems. Relatively, the solid–liquid reaction milling process is a more effective technique for formation of intermetallic compounds. 4. Summary Pure Al5 Mo, Al17 Mo4 and some other Al–Mo intermetallic compound powders which cannot be produced by the conventional mechanical alloying under a similar condition have been successfully synthesized by solid–liquid reaction ball milling. Acknowledgements
Fig. 3. The schematic diagram of formation mechanism for nano-size intermetallic compound powder by solid–liquid reaction ball milling.
The authors are grateful to the National Natural Science Foundation of China (Project 50574039) and the Doctorate Fund granted by Ministry of Education of China (20070532016) for financial support of this research. References
ders. Schematic diagram describing the formation mechanism of nano-size intermetallic compound powder is shown in Fig. 3. As a reaction milling process, the novel approach shows a significant difference from the conventional mechanical alloying, such as high-energy ball milling and tumbler milling. The former involves a direct reaction while the latter mainly involves the kneading of powders and the diffusion of atoms. Consequently, solid–liquid reaction ball milling possesses a higher reaction rate than the traditional mechanical alloying. Furthermore, when the alloy systems with intermetallic phases in the phase diagrams are treated by the traditional high-energy ball milling, amorphous phase rather than intermetallics are preferable and the direct formation of intermetal-
[1] M. Zduji, K.F. Kobayashi, P.H. Shingu, J. Mater. Sci. 26 (1991) 5502–5508. [2] M. Zduji, D. Poleti, L. Karanovi, K.F. Kobayashi, P.H. Shingu, Mater. Sci. Eng. A 185 (1994) 77–86. [3] M. Monagheddu, F. Delogu, L. Schiffini, R. Frattini, S. Enzo, Nanostruct. Mater. 11 (1999) 1253–1261. [4] Z.H. Chen, D. Chen, Mechanical Alloying and Solid–Liquid Reaction Ball Milling, Chemistry Industry Press, Beijing, 2006 (in Chinese). [5] D. Chen, J.H. Chen, H.G. Yan, Z.H. Chen, Mater. Sci. Eng. A 444 (2007) 1–5. [6] Z.H. Chen, D. Chen, G. Chen, H.G. Yan, P.Y. Huang, J. Alloys Compd. 307 (2004) 43–46. [7] D. Chen, G.L. Chen, N. Song, G. Chen, H.G. Yan, Z.H. Chen, J. Alloys Compd. 457 (2008) 292–295. [8] D. Chen, Z.H. Chen, J.H. Chen, P.Y. Huang, J. Alloys Compd. 376 (2004) 89– 94. [9] D. Chen, Z. Chen, J.G. Cai, Z.H. Chen, J. Alloys Compd. 461 (2008) L23–L25.
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom
Letter
Preparation of Al–Mo intermetallic powders by solid–liquid reaction ball milling Ding Chen a,∗ , Jianguo Cai a , Jianjun Fang b , Zhenhua Chen a a b
School of Material Science and Engineering, Hunan University, Changsha 410082, PR China College of Electromechanical Engineering, North China University of Technology, Beijing 100041, PR China
a r t i c l e
i n f o
Article history: Received 21 April 2009 Received in revised form 19 May 2009 Accepted 21 May 2009 Available online 28 May 2009 Keywords: Al–Mo alloy Intermetallic compound powder Solid–liquid reaction milling Mechanochemical effect
a b s t r a c t A series of Al–Mo intermetallic compound powders like Al12 Mo, Al5 Mo, Al22 Mo5 and Al17 Mo4 were been synthesized respectively at different temperatures by solid–liquid reaction ball milling, a novel mechanochemical approach. The as-milled products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show that single phase Al5 Mo and Al17 Mo4 intermetallic compound powders with an average diameter less than 100 nm may be obtained at 953 K after milling for 6 and 24 h, respectively. Finally, this paper discusses solid–liquid reaction mechanism and phase formation regularity in the milling process. © 2009 Elsevier B.V. All rights reserved.
1. Introduction The melting point and the density of molybdenum are 2896 K and 10.22 g/cm3 , respectively, and extremely different from those of aluminum which are 933 K and 2.70 g/cm3 . Obviously, the alloying of such two incompatible elements by melting process faces considerable challenges. These obstacles may be overcome by the formation of composite material using repeated fracture and cold welding of constituent powders. Some literatures on mechanical alloying of Al–Mo alloy system have been released in the past decades. Zdujic et al. reported annealing of mechanically alloyed Al73 Mo27 powders using methanol as a lubricant agent and found that intermetallic compound is formed at 973 K and may be evolved to single phase Al8 Mo3 by subsequent annealing treatment of 1373 K [1]. Meanwhile, Their works also showed that Al12 Mo and Al5 Mo phases can be obtained by annealing the mechanically treated Al90 Mo10 powders at 748 and 973 K, respectively, and Al4 Mo phase is formed by annealing the Al80 Mo20 powders. However, no intermetallic compound but the nanocrystalline structure and amorphous phase were synthesized in their studies, even when the milling time was extended to 1000 h [2]. Monagheddu et al. found that the annealing of mechanically treated Al75 Mo25 powders actually produced icosahedral–quasicrystalline phase which is a lower order structure than Al–Mo intermetallic compound phases which were not obtained at milling time up to 57 h [3]. These lit-
∗ Corresponding author. Tel.: +86 731 8821648; fax: +86 731 8821648. E-mail address: [email protected] (D. Chen). 0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2009.05.113
eratures show it is difficult to directly prepare the intermetallic phases of Al–Mo binary alloy system using common mechanical alloying method. In general, the post-annealing process is necessary to obtain a full intermetallic compound phase powders. Recently, a novel mechanochemical approach called solid–liquid reaction ball milling has been introduced by Chen and Chen [4]. A series of single intermetallic compound powders, like Fe13 Sn, Fe11 Zn40 , FeSb, Cu3 Sn, TiAl3 , Al4 W, Al13 Cu4 Fe and Al8 Fe2 Si, have been successfully obtained by this novel approach [5–9]. The average size of these intermetallic powders is less than 100 nm. In this paper, some Al–Mo intermetallic compound powders, such as Al12 Mo, Al5 Mo, Al22 Mo5 and Al17 Mo4 , are synthesized using this approach.
2. Experiment The solid–liquid reaction milling process is conducted at selected temperature in a solid–liquid reaction milling device in which a sealed milling cylinder with a diameter of 300 mm rotates in a resistance heated furnace equipped with a thermostatic system. Both balls and milling cylinder are made of the same original material to prevent melting from contamination. Mo–Al system was investigated in this paper. Al is served as the reactant due to its lower melting point. The milling cylinder is vacuumed and then filled with pure inertial gas (argon) to avoid oxidation of metals during milling at high temperature. The total mass of reactant is 50 g. The mass ratio of balls to reactant is 14:1 and rotation speed of the cylinder is 80 rpm. The temperature of milling is higher than melting point of Al to keep it at a molten state. The experimental detail has been previously described in Ref. [5].
L10
D. Chen et al. / Journal of Alloys and Compounds 485 (2009) L9–L11 Table 1 The as-milled production of Al–Mo alloy system for solid–liquid reaction ball milling. Temperature (K)
943 993 1073
Milling (time/h) 6
12
24
Al12 Mo, Al5 Mo Al5 Mo Al5 Mo, Al22 Mo5 , Al17 Mo4
Al5 Mo (mostly), Al22 Mo5 Al5 Mo, Al17 Mo4 Al17 Mo4 (mostly), Al5 Mo
Al17 Mo4 (mostly), Al5 Mo Al17 Mo4 Al17 Mo4
X-ray diffraction (XRD) measurement was performed using a diffractometer with Cu K␣ radiation. The morphologies and microstructures of the as-synthesized samples were observed by scanning electron microscopy (SEM, JSM-6700F) and transmission electron microscopy (TEM, JEM-3010). 3. Results and discussion 3.1. X-ray diffractometry and morphology The XRD results of the Al–Mo alloy system produced by solid–liquid reaction ball milling process under various conditions are shown in Table 1. It can be concluded that Al12 Mo, Al5 Mo,
Al22 Mo5 and Al17 Mo4 intermetallic phases were synthesized with different milling time at different temperatures. For instance, single phase Al5 Mo, the mixture of Al5 Mo and Al17 Mo4 , and single phase Al17 Mo4 were obtained at 993 K by milling 6, 12 and 24 h respectively. Fig. 1 shows the XRD patterns of the as-milled products of Al–Mo system at 993 K at different milling time. The milling temperature and milling time affect the component of the as-milled products based on XRD results. Al–Mo intermetallic compound powders with a higher Mo content can be formed more easily at higher temperature and longer milling time. The typical morphology of Al–Mo intermetallic compound powders obtained by solid–liquid reaction ball milling is shown in Fig. 2. The average size of particles is less than 100 nm. 3.2. Mechanism of solid–liquid reaction ball milling
Fig. 1. XRD pattern of as-milled products of Al–Mo system at 993 K after different milling time.
As mentioned above, Al–Mo intermetallics are difficult to synthesize by common process. Generally, the metals must be heated to certain temperatures above their melting points and then cooled down for the preparation of intermetallics. However, some Al–Mo intermetallic compounds were obtained by solid–liquid reaction ball milling process at a temperature far lower than the melting point of molybdenum, indicating that its mechanism for the formation of intermetallic phases is different from the traditional mechanism. The possible mechanism is discussed as follows. Based on the principle of mechanochemistry, the continuous collisions between the milling balls and liquid during milling process can induce chemical reactions on the surface of the milling balls. The reaction product can be immediately peeled off from the ball surface and enters into liquid to form ultrafine particles. Because there are a number of fine crystals in the liquid at the same time due to fracturing effect of milling, it is not easy for agglomeration of particles in the melt. That is the reason why the ultimate product of solid–liquid reaction milling is ultrafine pow-
Fig. 2. Typical morphology of Al–Mo intermetallic compound powder (Al5 Mo) obtained by solid–liquid reaction ball milling: (a) SEM image and (b) TEM image.
D. Chen et al. / Journal of Alloys and Compounds 485 (2009) L9–L11
L11
lic phases are only observed in few alloy systems. Relatively, the solid–liquid reaction milling process is a more effective technique for formation of intermetallic compounds. 4. Summary Pure Al5 Mo, Al17 Mo4 and some other Al–Mo intermetallic compound powders which cannot be produced by the conventional mechanical alloying under a similar condition have been successfully synthesized by solid–liquid reaction ball milling. Acknowledgements
Fig. 3. The schematic diagram of formation mechanism for nano-size intermetallic compound powder by solid–liquid reaction ball milling.
The authors are grateful to the National Natural Science Foundation of China (Project 50574039) and the Doctorate Fund granted by Ministry of Education of China (20070532016) for financial support of this research. References
ders. Schematic diagram describing the formation mechanism of nano-size intermetallic compound powder is shown in Fig. 3. As a reaction milling process, the novel approach shows a significant difference from the conventional mechanical alloying, such as high-energy ball milling and tumbler milling. The former involves a direct reaction while the latter mainly involves the kneading of powders and the diffusion of atoms. Consequently, solid–liquid reaction ball milling possesses a higher reaction rate than the traditional mechanical alloying. Furthermore, when the alloy systems with intermetallic phases in the phase diagrams are treated by the traditional high-energy ball milling, amorphous phase rather than intermetallics are preferable and the direct formation of intermetal-
[1] M. Zduji, K.F. Kobayashi, P.H. Shingu, J. Mater. Sci. 26 (1991) 5502–5508. [2] M. Zduji, D. Poleti, L. Karanovi, K.F. Kobayashi, P.H. Shingu, Mater. Sci. Eng. A 185 (1994) 77–86. [3] M. Monagheddu, F. Delogu, L. Schiffini, R. Frattini, S. Enzo, Nanostruct. Mater. 11 (1999) 1253–1261. [4] Z.H. Chen, D. Chen, Mechanical Alloying and Solid–Liquid Reaction Ball Milling, Chemistry Industry Press, Beijing, 2006 (in Chinese). [5] D. Chen, J.H. Chen, H.G. Yan, Z.H. Chen, Mater. Sci. Eng. A 444 (2007) 1–5. [6] Z.H. Chen, D. Chen, G. Chen, H.G. Yan, P.Y. Huang, J. Alloys Compd. 307 (2004) 43–46. [7] D. Chen, G.L. Chen, N. Song, G. Chen, H.G. Yan, Z.H. Chen, J. Alloys Compd. 457 (2008) 292–295. [8] D. Chen, Z.H. Chen, J.H. Chen, P.Y. Huang, J. Alloys Compd. 376 (2004) 89– 94. [9] D. Chen, Z. Chen, J.G. Cai, Z.H. Chen, J. Alloys Compd. 461 (2008) L23–L25.