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A new fabrication method to improve metal matrix composite dispersibility
Materials Letters 89 (2012) 279–282
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
A new fabrication method to improve metal matrix composite dispersibility Yun-Soo Lee a,b, Byeong-Hoon Yeon a,c, Soong-Keun Hyun a,n, Ki-Ju Kang d a
Division of Materials Science and Engineering, Inha University, Incheon 402-751, Korea Light Metal Division, Korea Institute of Materials Science, Changwon 642-831, Korea Functional Material R&D Team, Heesung Metal Ltd., Incheon 405-310, Korea d School of Mechanical Systems Engineering, Chonnam National University, Gwangju 500-757, Korea b c
a r t i c l e i n f o
abstract
Article history: Received 18 May 2012 Accepted 24 July 2012 Available online 1 August 2012
A new type of periodic cellular metal called wire-woven bulk Kagome (WBK) was used as a precursor for creating the composite materials with improved dispersibility. Preheated and non-preheated preforms were placed into molds, and then molten aluminum was poured into them to fabricate composites. The effects of preheating on the wettability and interfacial reaction between the aluminum matrix and the WBK preform were then investigated. The preheated preform composite had good wettability compared to the non-preheated preform composite. Interfacial phenomena between the aluminum matrix and the WBK preform were observed. Our research offers a new avenue for solving the problem of composite material dispersibility. & 2012 Elsevier B.V. All rights reserved.
Keywords: Aluminum matrix composites Wire-woven bulk Kagome Dispersibility Preform
1. Introduction Metal matrix composites (MMCs) have attracted much attention due to their unique properties such high specific strength, specific modulus, stiffness, wear resistance and lower coefficient of thermal expansion [1–3]. These properties make them attractive for a variety of applications, such as in the aerospace, military and automotive industries. However, these properties cannot be conferred to an entire composite since it has not been possible to distribute reinforcement evenly throughout it’s entirely. One method for improving MMC dispersiblity is to use preform [4–7]. Marchi et al. [4] examine Al2O3–Al interpenetrating-phase composites that can be created by using 3-D periodic Al2O3 preform fabricated by robotic deposition. Asano et al. [5] fabricated aluminum alloy composites reinforced with short potassium titanate fiber preform by improving squeeze casting. Kang et al. [8–10] fabricated successfully a new type of periodic cellular metal named wire-woven bulk Kagome (WBK) using continuous helical wires. This structure has high specific strength and periodicity. Furthermore, the volume fraction of a WBK structure can be controlled easily to change its wire pitch and diameter. In this study, WBK structures were used as a preform to improve composite dispersibility, which is a pressing problem with respect to manufacturing quality. Stainless steel SUS 304 wires were selected for the WBK preform because their interfacial adhesion with aluminum is good. The microstructure, wettability n
Corresponding author. Tel.: þ82 32 860 7547; fax: þ82 32 862 5546. E-mail address: [email protected] (S.-K. Hyun).
0167-577X/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2012.07.096
and interfacial reaction between the aluminum matrix and the WBK preform were examined in detail.
2. Material and methods 2.1. WBK preform WBK preform was fabricated using continuous helical wires. Stainless steel SUS 304 wires 0.78 mm in diameter were twisted until plastic deformation occurred. They were then assembled methodically in six different directions according to a previously described procedure [8]. In brief, the fabrication of WBK preform is a continuous process comprising a series of plastic deformation of wire (fabrication of helical wires), and in-plane assembly and out-of-plane assembly stages. The assembled WBK preforms were preheated at 623 K for 30 min to examine the effect of preheating on wettability between the matrix and the preform. 2.2. Al-WBK composites For each composite, pure aluminum (99.9 wt% Al) was melted at 973 K by using medium wave frequency induction melting furnace. At the same time, an SS400 steel mold was preheated for dehydrating using a gas torch. The parting agent was applied to the inside of the mold, and then the WBK preform was placed into the mold. Molten aluminum was poured into the mold to fabricate the Al-WBK composites in the open air. At this time, the temperature of the preheated mold was 523 K. The fabrication processes are summarized in Fig. 1(a).
280
Y.-S. Lee et al. / Materials Letters 89 (2012) 279–282
Fig. 1. (a) Schematic of fabrication process, (b) surface wettability between aluminum matrix and non-preheated preform and (c) surface wettability between aluminum matrix and preheated preform at 624 K for 30 min.
The Al-WBK composites were cut using a precision cut-off machine (Accutom-50, Struers GmbH, Copenhagen, Denmark). Each specimen was polished using a series of emery papers. The microstructure and wettability between the aluminum matrix and the WBK preform were observed using an optical microscope (VHX-200, KEYENCE Co., Japan). The chemical elements near the interface were determined using an energy dispersive X-ray spectroscope attached to scanning electron microscope (JSM5500, JEOL Co., Japan). Hardness measurements were performed using a micro-Vickers hardness tester (HM-124, Akashi Co., Japan) under a load of 25 g for 10 s.
3. Results and discussion 3.1. Interface wettability We first examined the effect of preheating on the wettability of the aluminum matrix and WBK preform interface. When the wires were in intimate contact in the non-preheated preform, the exterior region had good wettability but the interior region had poor wettability associated with large voids as shown in Fig. 1(b). For the preheated preform, the exterior and interior regions as well as the interfacial reaction zone between the matrix and the preform had good wettability, as detailed in Fig. 1(c). These results can be explained by the effect of preheating on the interfacial tension. According to Young’s equation [11], the relationship among the horizontal components of the three interfacial tensions of such the three-phase contact system can be expressed as
gPV ¼ gPA þ gAV cos y
ð1Þ
Here, g is the interfacial tension between the preform-vapor (PV), the preform-molten aluminum (PA), and the molten aluminumvapor (AV) phases, and y is the contact angle. The wettability is increased with decreasing y which decreases with increasing gPV and decreasing gPA and gAV. Of these parameters, gPA can be controlled by preheating the preform because it is predominantly influenced by temperature [12]. The temperature gradient
between the preheated preform and the matrix was small. Therefore, the wettability of the preheated preform was better than that of the non-preheated preform because of the comparatively high temperature of the contacting aluminum melt. 3.2. Interfacial reaction zone To improve the unique properties of composite materials, it is necessary to control what occurs in the interfacial reaction zone. In general, this zone degrades the properties of MMCs due to its brittleness. However, a proper zone thickness, which can be controlled by solidification rate and post heat treatment, is necessary to optimize fully the pull-out resistance and strength of the composite [13–15]. Therefore, we performed hardness tests and a chemical analysis to confirm the presence of the interfacial reaction zone. The micro-Vickers hardness of the composite was measured near the interface to confirm that an interfacial reaction had occurred. When the preform was not preheated, the matrix and the WBK preform exhibited identical hardness values as depicted in Fig. 2(a). The change in the hardness from the preform to the matrix is shown in Fig. 2(b). The hardness of the interfacial reaction zone was much greater than those of the preform and the matrix. The distribution of the hardness from the inner area to the outer area of the interfacial reaction zone indicates that multiple phases existed. We carried out an EDX micro-chemical analysis near the interfacial reaction zone. The reaction zone did not form when the preform was not preheated and each composition was inherent to its particular zone, as shown in Fig. 3(a). However, interface reaction was confirmed to have taken place when the preform was preheated, as shown in Fig. 3(b). It is possible that the reaction zone was a mixture of Fe(Cr, Ni)Al2, Fe(Cr, Ni)Al3 and (Fe, Cr, Ni)2Al7 [16]. The percentage of the individual intermetallic compounds at various locations in the reaction zone was different, and therefore resulted in the hardness distribution shown in Fig. 2(b). Based on the hardness test and EDX analysis, we confirmed the presence of a reaction zone. These results indicate that an
Y.-S. Lee et al. / Materials Letters 89 (2012) 279–282
Fig. 2. Cross-sectional micro-Vickers hardness profile near interface between aluminum matrix and (a) non-preheated preform, and (b) preheated preform.
interfacial chemical reaction can occur to a sufficient extent between the molten aluminum and the preform because the solidification rate was delayed by the low temperature gradient. A high degree of wettability, as described in Section 3.1, was necessary for the interfacial chemical reaction to occur.
281
Fig. 3. EDX micro-chemical analysis of Al, Fe, Ni, and Cr concentrations near interface between aluminum matrix and (a) non-preheated preform, and (b) preheated preform.
tion and the results of a chemical analysis of the interface. Our research offers a new means for solving the problem of dispersibility in composite materials.
4. Conclusions
Acknowledgment
A new fabrication method for MMCs is proposed to improve the dispersibility of composite materials. For this, the periodic cellular metal WBK was used as a preform. The effects of the preform and preheating on the wettability and interfacial reaction between the matrix and the preform were investigated. We achieved better wettability when using the preheated preform than using the non-preheated preform. In addition, the interfacial reaction between the aluminum matrix and the preform was confirmed to have taken place based on the hardness distribu-
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012007739) and by Inha University Research Grant. References [1] Miracle DB. Compos Sci Technol 2005;65:2526–40. [2] Han BQ, Huang JY, Zhu YT, Lavernia EJ. Scr Mater 2006;54:1175–80.
282
[3] [4] [5] [6] [7] [8] [9]
Y.-S. Lee et al. / Materials Letters 89 (2012) 279–282
Deng CF, Ma YX, Zhang P, Zhang XX, Wang DZ. Mater Lett 2008;62:2301–3. Marchi CS, Kouzeli M, Rao R, Lewis JA, Dunand DC. Scr Mater 2003;49:861–6. Asano K, Yoneda H, Agari Y. Mater Trans, JIM 2008;49:2264–9. Wannasin J, Flemings MC. J Mater Process Technol 2005;169:143–9. ˜ a A. Compos Part A 2010;41:1605–11. Sa´nchez M, Rams J, Uren Lee YH, Lee BK, Jeon IS, Kang KJ. Acta Mater 2007;55:6084–94. Kang KJ. Acta Mater 2009;57:1865–74.
[10] [11] [12] [13] [14] [15] [16]
Lee BK, Kang KJ. Scr Mater 2009;60:391–4. Young T. Philos Trans R Soc London 1805;95:65–87. Harley Y, Jennings JR. J Colloid Interface Sci 1967;24:323–9. Baik KH. Mater Sci Eng A 2003;355:79–87. Calow CA, Porter IT. J Mater Sci 1971;6:156–63. Lee SM, Lee HJ, Hong CP. J Korean Inst Met Mater 1990;28:225–34. Hwang YH, Horng CF, Lin SJ, Liu KS, Jahn MT. J Mater Sci 1997;32:719–25.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
A new fabrication method to improve metal matrix composite dispersibility Yun-Soo Lee a,b, Byeong-Hoon Yeon a,c, Soong-Keun Hyun a,n, Ki-Ju Kang d a
Division of Materials Science and Engineering, Inha University, Incheon 402-751, Korea Light Metal Division, Korea Institute of Materials Science, Changwon 642-831, Korea Functional Material R&D Team, Heesung Metal Ltd., Incheon 405-310, Korea d School of Mechanical Systems Engineering, Chonnam National University, Gwangju 500-757, Korea b c
a r t i c l e i n f o
abstract
Article history: Received 18 May 2012 Accepted 24 July 2012 Available online 1 August 2012
A new type of periodic cellular metal called wire-woven bulk Kagome (WBK) was used as a precursor for creating the composite materials with improved dispersibility. Preheated and non-preheated preforms were placed into molds, and then molten aluminum was poured into them to fabricate composites. The effects of preheating on the wettability and interfacial reaction between the aluminum matrix and the WBK preform were then investigated. The preheated preform composite had good wettability compared to the non-preheated preform composite. Interfacial phenomena between the aluminum matrix and the WBK preform were observed. Our research offers a new avenue for solving the problem of composite material dispersibility. & 2012 Elsevier B.V. All rights reserved.
Keywords: Aluminum matrix composites Wire-woven bulk Kagome Dispersibility Preform
1. Introduction Metal matrix composites (MMCs) have attracted much attention due to their unique properties such high specific strength, specific modulus, stiffness, wear resistance and lower coefficient of thermal expansion [1–3]. These properties make them attractive for a variety of applications, such as in the aerospace, military and automotive industries. However, these properties cannot be conferred to an entire composite since it has not been possible to distribute reinforcement evenly throughout it’s entirely. One method for improving MMC dispersiblity is to use preform [4–7]. Marchi et al. [4] examine Al2O3–Al interpenetrating-phase composites that can be created by using 3-D periodic Al2O3 preform fabricated by robotic deposition. Asano et al. [5] fabricated aluminum alloy composites reinforced with short potassium titanate fiber preform by improving squeeze casting. Kang et al. [8–10] fabricated successfully a new type of periodic cellular metal named wire-woven bulk Kagome (WBK) using continuous helical wires. This structure has high specific strength and periodicity. Furthermore, the volume fraction of a WBK structure can be controlled easily to change its wire pitch and diameter. In this study, WBK structures were used as a preform to improve composite dispersibility, which is a pressing problem with respect to manufacturing quality. Stainless steel SUS 304 wires were selected for the WBK preform because their interfacial adhesion with aluminum is good. The microstructure, wettability n
Corresponding author. Tel.: þ82 32 860 7547; fax: þ82 32 862 5546. E-mail address: [email protected] (S.-K. Hyun).
0167-577X/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2012.07.096
and interfacial reaction between the aluminum matrix and the WBK preform were examined in detail.
2. Material and methods 2.1. WBK preform WBK preform was fabricated using continuous helical wires. Stainless steel SUS 304 wires 0.78 mm in diameter were twisted until plastic deformation occurred. They were then assembled methodically in six different directions according to a previously described procedure [8]. In brief, the fabrication of WBK preform is a continuous process comprising a series of plastic deformation of wire (fabrication of helical wires), and in-plane assembly and out-of-plane assembly stages. The assembled WBK preforms were preheated at 623 K for 30 min to examine the effect of preheating on wettability between the matrix and the preform. 2.2. Al-WBK composites For each composite, pure aluminum (99.9 wt% Al) was melted at 973 K by using medium wave frequency induction melting furnace. At the same time, an SS400 steel mold was preheated for dehydrating using a gas torch. The parting agent was applied to the inside of the mold, and then the WBK preform was placed into the mold. Molten aluminum was poured into the mold to fabricate the Al-WBK composites in the open air. At this time, the temperature of the preheated mold was 523 K. The fabrication processes are summarized in Fig. 1(a).
280
Y.-S. Lee et al. / Materials Letters 89 (2012) 279–282
Fig. 1. (a) Schematic of fabrication process, (b) surface wettability between aluminum matrix and non-preheated preform and (c) surface wettability between aluminum matrix and preheated preform at 624 K for 30 min.
The Al-WBK composites were cut using a precision cut-off machine (Accutom-50, Struers GmbH, Copenhagen, Denmark). Each specimen was polished using a series of emery papers. The microstructure and wettability between the aluminum matrix and the WBK preform were observed using an optical microscope (VHX-200, KEYENCE Co., Japan). The chemical elements near the interface were determined using an energy dispersive X-ray spectroscope attached to scanning electron microscope (JSM5500, JEOL Co., Japan). Hardness measurements were performed using a micro-Vickers hardness tester (HM-124, Akashi Co., Japan) under a load of 25 g for 10 s.
3. Results and discussion 3.1. Interface wettability We first examined the effect of preheating on the wettability of the aluminum matrix and WBK preform interface. When the wires were in intimate contact in the non-preheated preform, the exterior region had good wettability but the interior region had poor wettability associated with large voids as shown in Fig. 1(b). For the preheated preform, the exterior and interior regions as well as the interfacial reaction zone between the matrix and the preform had good wettability, as detailed in Fig. 1(c). These results can be explained by the effect of preheating on the interfacial tension. According to Young’s equation [11], the relationship among the horizontal components of the three interfacial tensions of such the three-phase contact system can be expressed as
gPV ¼ gPA þ gAV cos y
ð1Þ
Here, g is the interfacial tension between the preform-vapor (PV), the preform-molten aluminum (PA), and the molten aluminumvapor (AV) phases, and y is the contact angle. The wettability is increased with decreasing y which decreases with increasing gPV and decreasing gPA and gAV. Of these parameters, gPA can be controlled by preheating the preform because it is predominantly influenced by temperature [12]. The temperature gradient
between the preheated preform and the matrix was small. Therefore, the wettability of the preheated preform was better than that of the non-preheated preform because of the comparatively high temperature of the contacting aluminum melt. 3.2. Interfacial reaction zone To improve the unique properties of composite materials, it is necessary to control what occurs in the interfacial reaction zone. In general, this zone degrades the properties of MMCs due to its brittleness. However, a proper zone thickness, which can be controlled by solidification rate and post heat treatment, is necessary to optimize fully the pull-out resistance and strength of the composite [13–15]. Therefore, we performed hardness tests and a chemical analysis to confirm the presence of the interfacial reaction zone. The micro-Vickers hardness of the composite was measured near the interface to confirm that an interfacial reaction had occurred. When the preform was not preheated, the matrix and the WBK preform exhibited identical hardness values as depicted in Fig. 2(a). The change in the hardness from the preform to the matrix is shown in Fig. 2(b). The hardness of the interfacial reaction zone was much greater than those of the preform and the matrix. The distribution of the hardness from the inner area to the outer area of the interfacial reaction zone indicates that multiple phases existed. We carried out an EDX micro-chemical analysis near the interfacial reaction zone. The reaction zone did not form when the preform was not preheated and each composition was inherent to its particular zone, as shown in Fig. 3(a). However, interface reaction was confirmed to have taken place when the preform was preheated, as shown in Fig. 3(b). It is possible that the reaction zone was a mixture of Fe(Cr, Ni)Al2, Fe(Cr, Ni)Al3 and (Fe, Cr, Ni)2Al7 [16]. The percentage of the individual intermetallic compounds at various locations in the reaction zone was different, and therefore resulted in the hardness distribution shown in Fig. 2(b). Based on the hardness test and EDX analysis, we confirmed the presence of a reaction zone. These results indicate that an
Y.-S. Lee et al. / Materials Letters 89 (2012) 279–282
Fig. 2. Cross-sectional micro-Vickers hardness profile near interface between aluminum matrix and (a) non-preheated preform, and (b) preheated preform.
interfacial chemical reaction can occur to a sufficient extent between the molten aluminum and the preform because the solidification rate was delayed by the low temperature gradient. A high degree of wettability, as described in Section 3.1, was necessary for the interfacial chemical reaction to occur.
281
Fig. 3. EDX micro-chemical analysis of Al, Fe, Ni, and Cr concentrations near interface between aluminum matrix and (a) non-preheated preform, and (b) preheated preform.
tion and the results of a chemical analysis of the interface. Our research offers a new means for solving the problem of dispersibility in composite materials.
4. Conclusions
Acknowledgment
A new fabrication method for MMCs is proposed to improve the dispersibility of composite materials. For this, the periodic cellular metal WBK was used as a preform. The effects of the preform and preheating on the wettability and interfacial reaction between the matrix and the preform were investigated. We achieved better wettability when using the preheated preform than using the non-preheated preform. In addition, the interfacial reaction between the aluminum matrix and the preform was confirmed to have taken place based on the hardness distribu-
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012007739) and by Inha University Research Grant. References [1] Miracle DB. Compos Sci Technol 2005;65:2526–40. [2] Han BQ, Huang JY, Zhu YT, Lavernia EJ. Scr Mater 2006;54:1175–80.
282
[3] [4] [5] [6] [7] [8] [9]
Y.-S. Lee et al. / Materials Letters 89 (2012) 279–282
Deng CF, Ma YX, Zhang P, Zhang XX, Wang DZ. Mater Lett 2008;62:2301–3. Marchi CS, Kouzeli M, Rao R, Lewis JA, Dunand DC. Scr Mater 2003;49:861–6. Asano K, Yoneda H, Agari Y. Mater Trans, JIM 2008;49:2264–9. Wannasin J, Flemings MC. J Mater Process Technol 2005;169:143–9. ˜ a A. Compos Part A 2010;41:1605–11. Sa´nchez M, Rams J, Uren Lee YH, Lee BK, Jeon IS, Kang KJ. Acta Mater 2007;55:6084–94. Kang KJ. Acta Mater 2009;57:1865–74.
[10] [11] [12] [13] [14] [15] [16]
Lee BK, Kang KJ. Scr Mater 2009;60:391–4. Young T. Philos Trans R Soc London 1805;95:65–87. Harley Y, Jennings JR. J Colloid Interface Sci 1967;24:323–9. Baik KH. Mater Sci Eng A 2003;355:79–87. Calow CA, Porter IT. J Mater Sci 1971;6:156–63. Lee SM, Lee HJ, Hong CP. J Korean Inst Met Mater 1990;28:225–34. Hwang YH, Horng CF, Lin SJ, Liu KS, Jahn MT. J Mater Sci 1997;32:719–25.