- Email: [email protected]
SiCp composite foams
Materials Science and Engineering A 457 (2007) 325–328
Compressive behavior and damping property of ZA22/SiCp composite foams Yu Sirong ∗ , Liu Jiaan, Luo Yanru, Liu Yaohui Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, and College of Materials Science and Engineering, Jilin University, Changchun 130025, PR China Received 18 October 2006; received in revised form 7 December 2006; accepted 19 December 2006
Abstract The ZA22 alloy composite foams reinforced by 10 vol.% SiC particles (ZA22/SiCp composite foams) were fabricated with the melt foaming route using CaCO3 blowing agent in this paper. The compressive behavior and damping property of the composite foams were investigated. The results show that SiC particles dispersing in cell walls can alter the deformation mechanism of ZA22 foams. The plateau stress of the composite foams, therefore, fluctuated continually. The damping properties of ZA22/SiCp composite foams are obviously higher than those of ZA22 alloy and ZA22 foams. The addition of SiC particles can improve the damping capacity of ZA22 foams because SiC particles introduce multifarious interfaces and high-density dislocations in composite foams. © 2007 Elsevier B.V. All rights reserved. Keywords: ZA22 alloy; SiC particles; Metal foams; Compressive behavior; Damping property
1. Introduction Recently, metallic foams have received extensive interest as new structural and functional materials because of their high specific strength, energy absorption, flame resistance, vibration reduction, and sound absorption [1]. Therefore, they can be widely used in construction, transportation and aerospace industry [1,2]. Metal can be foamed in many methods [1,4–7]. Direct foaming methods of metal melts are quite suitable for industrial production because of their handleability and low cost [1,3], but the cell structure of metallic foams is irregular and the cell size is inhomogeneous. So, it is necessary to increase the viscosity of metal melts in order to prevent gas bubble from escaping and coalescing. Addition of ceramic particles such as SiC, MnO2 , and Al2 O3 to metal melts is a good approach for increasing the viscosity [1,3]. For example, the recently developed FORMGRIP/FOAMCARP process, which was based on the remelting of metal matrix composites (SiCp /Al), is suitable for producing metal foams [5,6]. Most of previous researches about the effects of solid additive on the manufacture of metal
∗
Corresponding author. Tel.: +86 431 85095862; fax: +86 431 85095575. E-mail address: [email protected] (S. Yu).
0921-5093/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2006.12.089
foams were focused on the foaming physics. It was thought that ceramic particles changed the curvature of gas/liquid interface, increased the viscosity of melts, and stabilized the cell wall [7–9]. However, the studies about the effects of the ceramic particles on the structure and properties of metal foams were very few. Sigimura et al. [10] confirmed that the microstructures of Al matrix composite foams were similar to those of ceramic particle reinforced Al matrix composites. Parkash et al. [11] investigated the compressive characteristics of Al/SiCp composite foams and found that the localized deformation took place due to the existence of SiCp in cell wall. Gui et al. [12,13] found that A356/SiCp composite foams exhibited a typical brittle characteristic and had better damping and sound absorption properties than Al foams because of the existence of Al/SiCp interfaces. Zn and Zn alloy foams possess excellent mechanical behaviors and damping properties at room temperature [14–16]. However, the work on closed-cell Zn foams prepared with the direct foaming method of melt, to date, is few, and the study on Zn matrix composite foams has not been reported yet. Consequently, it is necessary to investigate various characters (especially functional properties) of Zn and Zn matrix composite foams in order to widen the applying field of metallic foams.
326
S. Yu et al. / Materials Science and Engineering A 457 (2007) 325–328
The purpose of this work is to study the compressive behavior and damping property of ZA22/SiCp composite foams and reveal their mechanisms. 2. Experimental 2.1. Raw materials The raw materials for preparing composite foams included ZA22 alloy (22.0 wt.%Al, 1.0 wt.%Cu, 0.03 wt.%Mg, and Zn balance), ZA22 alloy powders (about 40 m in size), SiC particles (98.0 wt.% in purity, about 28 m in size), and CaCO3 powders (99.5 wt.% in purity, about 44 m in size). SiC particles and CaCO3 powders were used as reinforcement and blowing agent, respectively. To improve the wettability between SiCp and ZA22 melt, SiC particles were heat-treated at 930 ◦ C for 6 h and then at 420 ◦ C for 2 h.
Fig. 1. Thermogravimetric analysis curve of CaCO3 powders.
gas bubbles. Finally the composite foams were cooled down in air.
2.2. Measure of decomposition temperature of blowing agent
2.4. Characterization of composite foams The decomposition reaction of CaCO3 blowing agent can be written as [19]: CaCO3(s) = CaO(s) + CO2(g)
(1)
In order to determine reasonable foaming temperature of ZA22 melt, the decomposition temperature of CaCO3 blowing agent has to be measured. So, CaCO3 blowing agent was studied with Thermogravimetric Analysis (Model DTA/TGRigaku-8150, Japan) under a protection of high pure argon. The heating rate was 20 ◦ C/min. 2.3. Fabrication of composite foams In order to make SiCp and CaCO3 powders enter ZA22 melt easily, powder preforms containing SiCp , ZA22 alloy powders, and CaCO3 powders (the mass ratio is 4:4:1) were prepared. Firstly these powders were blended for 5 h using a ball mill in a stainless steel container. Then the powder mixture was mechanically pressed into a cylindrical die at 20 MPa. The size of the compact preform is Ø 22 mm × 20 mm. Finally cylindrical preforms were baked at 150 ◦ C for 3 h in a vacuum drying oven to remove moisture. According to the thermogravimetric analysis curve of CaCO3 powders (Fig. 1), the beginning temperature of CO2 evolution is about 650 ◦ C. Therefore, when performs were added to ZA22 melt, the temperature of ZA22 melt cannot be more than 650 ◦ C in order to avoid the premature release of CO2 gas. ZA22 alloy was melted to 510 ◦ C in a crucible furnace, and then performs, whose adding amount was determined according to the designed volume fraction (10%) of SiCp in cell wall, were added to the melt. After that, the slurry was stirred for 10 min with a steel stirrer at a rate of 900 r/min to disperse SiC and CaCO3 particles homogeneously and then held at 700–710 ◦ C for 12 min to allow blowing agent to release
Microstructure and phases of the composite foams were analyzed by means of scanning electron microscopy (SEM) (Model JSM-5310, Japan) and X-ray diffraction (XRD) (Model D/Max 2500PC Rigaku, Japan). The porosities of composite foams were calculated using the following equation: ρ∗ P = 1− × 100% (2) ρs where P is the porosity of composite foams, ρ* and ρs are the densities of composite foams and the cell wall material, respectively, and ρ* /ρs , which is called the relative density of composite foams, indicates the ratio of the density of composite foams to the density of cell wall material. 2.5. Compression and damping test Specimens with the dimensions of 15 mm × 15 mm × 30 mm (used for compression test) and Ø 70 mm × 10 mm (used for damping test) were prepared with a wire cutting machine. The size of compressive specimens was chosen to guarantee at least six cells in each direction because samples with smaller dimension can cause a significant loss of mechanical properties [17]. The compressive tests were carried out on a universal mechanical testing machine at a nominal strain rate of 2.2 × 10−3 s−1 . The damping characteristic values were measured using free vibration method. The signal frequency was 400 Hz. The logarithmic decrement δ was used to describe the damping capacity of materials. δ is expressed as [18]: δ = ln
xn xn+1
where xn and xn+1 are amplitudes of successive cycles.
(3)
S. Yu et al. / Materials Science and Engineering A 457 (2007) 325–328
Fig. 2. Photographs of ZA22/10 vol.%SiCp composite foams: (a) optical photograph and (b) SEM photograph of cell wall.
327
Fig. 4. Compressive stress–strain curves of the ZA22 foams (a) and composite foams (b).
3. Results and discussion The microstructures of composite foam are shown in Fig. 2. It can be found that the structure of cells is uniform (Fig. 2(a)) and about 10 vol.% SiCp uniformly distribute in the cell wall of composite foams (Fig. 2(b)). The porosities of composite foams are from 80% to 93%. The XRD pattern of composite foams is shown in Fig. 3. It is clear that Al-rich phase, Zn-rich phase, and SiC exist in the composite foams.
Fig. 3. XRD pattern of ZA22/SiCp composite foams.
3.1. Compressive behaviors of the foams The compressive stress–strain curves of ZA22 foams and composite foams are shown in Fig. 4. It can be found that the stress–strain behaviors of different foams are very similar, which include three distinct regions, i.e., elastic region, plateau region, and densification region. ZA22 foams exhibited typical characteristics of plastic foams. Stress increased linearly with increasing strain in elastic deformation region. Then a long plateau of plastic deformation with slight stress fluctuation generated, during which cell walls buckled and collapsed. The plateau stress increased with increasing relative density (ρ* /ρs ). In densification region, the stress abruptly rose because cell walls contacted each other. Mechanical response of composite foams is more complex than that of ZA22 foams due to the introduction of ceramic particles. The width of plateau region was nearly as much as that of ZA22 foams. But the curves continually fluctuated with increasing strain, and the stress peak appeared time and again (Fig. 4(b)). The main reason is that SiCp in cell walls changed the deformation mechanism of cell walls. The stress concentration took place at SiCp /ZA22 alloy interface during compression test of composite foams. The magnitude of the stress concentration is different at different time and position, which resulted in the localized yielding of composite foams under compressive stress.
328
S. Yu et al. / Materials Science and Engineering A 457 (2007) 325–328
(2) The compressive stress–strain curves of ZA22 foams and composite foams have obvious elastics region, plateau region and densification region. The plateau stress of ZA22 foams increases with increasing relative density. The plateau stress of ZA22/SiCp composite foams fluctuates acutely because SiCp in cell walls alters the deformation mechanism of ZA22 alloy matrix. (3) The damping capacity of closed-cell ZA22 foams is slightly higher than that of ZA22 alloy. Whereas the damping properties of ZA22/SiCp composite foams are obviously higher than those of ZA22 alloy and ZA22 foams. The addition of SiCp can improve the damping capacity of ZA22 foams. Acknowledgements Fig. 5. Damping capacities of different materials. A: ZA22 alloy; B: ZA22 foams (ρ* /ρs = 0.168); C: ZA22 foams (ρ* /ρs = 0.161); D: ZA22/SiCp composite foams (ρ* /ρs = 0.215); E: ZA22/SiCp composite foams (ρ* /ρs = 0.192).
This work was supported by “Program for New Century Excellent Talents in University” and “985 project” of Jilin University of P.R. China.
The results mentioned above are very similar to those of Al matrix composite foams [11].
References
3.2. Damping properties The damping capacities of ZA22 alloy, ZA22 foams and ZA22/SiCp composite foams are given in Fig. 5. ZA22 alloy (A in Fig. 5) has high damping capacity. The damping mechanism of this kind of Zn–Al eutectoid alloy is known to arise from the phase boundary between soft Al-rich phase and rigid Znrich phase [20,21]. The damping properties of closed-cell ZA22 foams (B and C in Fig. 5) are slightly higher than that of ZA22 alloy. This is owing to a mass of macroscopic pores existing in ZA22 foams. The conversions of the stress mode took place in pore boundaries, and the stress concentration generated, which made pores expand and distort and resulted in the reduction of the vibration [22]. In addition, damping capacity could be also obtained by the friction between the crack surfaces of closedcell foams produced in high temperature [23]. The logarithmic decrements of the composite foams (D and E in Fig. 5) were obviously higher than those of ZA22 alloy and ZA22 foams. The main reason is that there were multifarious interfaces and high-density dislocations in composite foams owing to the introduction of SiCp , which resulted in the dislocation damping and interface damping. 4. Conclusions (1) ZA22/10 vol.%SiCp composite foams with porosities from 80% to 93% were fabricated by means of melt foaming route using CaCO3 blowing agent.
[1] J. Banhart, Prog. Mater. Sci. 46 (2001) 559. [2] J. Gibson, M.F. Ashby, Cellular Solids: Structure and Properties, Cambridge University Press, Cambridge, 1997. [3] H.P. Degischer, Handbook of Cellular Metals, Wiley/VCH Gerlag GmbH, 2002. [4] B. Jiang, N.Q. Zhao, C.S. Shi, et al., Mater. Lett. 59 (2005) 3333–3336. [5] V. Gergely, T.W. Clyne, Adv. Eng. Mater. 2 (2000) 175. [6] V. Gergely, D.C. Curran, T.W. Clyne, Comp. Sci. Technol. 63 (2003) 2301–2310. [7] S.W. Ip, Y. Wang, J.M. Toguri, Can. Met. Quart. 38 (1999) 81–92. [8] Y.Q. Sun, T. Gao, Metall. Trans. 33A (2002) 3285– 3292. [9] Kaptay, Colloids Surf. A: Physicochem. Eng. Aspects 230 (2004) 67– 80. [10] Y. Sigimura, J. Meyer, M.Y. He, et al., Acta Mater. 45 (1999) 5245– 5259. [11] O. Parkash, H. Sang, J.D. Embury, Mater. Sci. Eng. A 199 (1995) 195–203. [12] M.C. Gui, D.B. Wang, J.J. Wu, et al., Mater. Sci. Eng. A 286 (2000) 282–288. [13] J. Wu, C. Li, D. Wang, M. Gui, Comp. Sci. Technol. 63 (2003) 569– 574. [14] P.H. Thornton, C.L. Magee, Metall. Trans. 6A (1975) 1801–1807. [15] J. Kov´ae` ik, F. Siman`e´ık, Kovov´e Materi´aly 42 (2004) 70–90. [16] J.N. Wei, Z.B. Li, F.S. Han, Phys Status Solidi A 191 (2002) 435–444. [17] E. Andrews, G. Gioux, P. Onck, J. Gibson, Int. J. Mech. Sci. 43 (2001) 701–714. [18] D.P. Dai, Technical Application of Damping Technology, Tsinghua University Press, Beijing, 1991. [19] M.W.J. Chase, NIST-JANAF Thermochemical Tables, American Chemical Society/American Institute of Physics, Gaithersburg, MD, USA, 1998. [20] I.G. Ritchie, Z.L. Pan, F.E. Goodman, Metall. Trans. 22A (1991) 617– 622. [21] K. Nuttall, J. Inst. Met. 99 (1971) 266–270. [22] J. Zhang, M.N. Gungor, E.J. Lavernia, J. Mater. Sci. 28 (1993) 1515. [23] B. Zettl, S. Stanzl-Tschegg, Materwiss. Werkstofftechn. 4 (2000) 210–214.
Compressive behavior and damping property of ZA22/SiCp composite foams Yu Sirong ∗ , Liu Jiaan, Luo Yanru, Liu Yaohui Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, and College of Materials Science and Engineering, Jilin University, Changchun 130025, PR China Received 18 October 2006; received in revised form 7 December 2006; accepted 19 December 2006
Abstract The ZA22 alloy composite foams reinforced by 10 vol.% SiC particles (ZA22/SiCp composite foams) were fabricated with the melt foaming route using CaCO3 blowing agent in this paper. The compressive behavior and damping property of the composite foams were investigated. The results show that SiC particles dispersing in cell walls can alter the deformation mechanism of ZA22 foams. The plateau stress of the composite foams, therefore, fluctuated continually. The damping properties of ZA22/SiCp composite foams are obviously higher than those of ZA22 alloy and ZA22 foams. The addition of SiC particles can improve the damping capacity of ZA22 foams because SiC particles introduce multifarious interfaces and high-density dislocations in composite foams. © 2007 Elsevier B.V. All rights reserved. Keywords: ZA22 alloy; SiC particles; Metal foams; Compressive behavior; Damping property
1. Introduction Recently, metallic foams have received extensive interest as new structural and functional materials because of their high specific strength, energy absorption, flame resistance, vibration reduction, and sound absorption [1]. Therefore, they can be widely used in construction, transportation and aerospace industry [1,2]. Metal can be foamed in many methods [1,4–7]. Direct foaming methods of metal melts are quite suitable for industrial production because of their handleability and low cost [1,3], but the cell structure of metallic foams is irregular and the cell size is inhomogeneous. So, it is necessary to increase the viscosity of metal melts in order to prevent gas bubble from escaping and coalescing. Addition of ceramic particles such as SiC, MnO2 , and Al2 O3 to metal melts is a good approach for increasing the viscosity [1,3]. For example, the recently developed FORMGRIP/FOAMCARP process, which was based on the remelting of metal matrix composites (SiCp /Al), is suitable for producing metal foams [5,6]. Most of previous researches about the effects of solid additive on the manufacture of metal
∗
Corresponding author. Tel.: +86 431 85095862; fax: +86 431 85095575. E-mail address: [email protected] (S. Yu).
0921-5093/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2006.12.089
foams were focused on the foaming physics. It was thought that ceramic particles changed the curvature of gas/liquid interface, increased the viscosity of melts, and stabilized the cell wall [7–9]. However, the studies about the effects of the ceramic particles on the structure and properties of metal foams were very few. Sigimura et al. [10] confirmed that the microstructures of Al matrix composite foams were similar to those of ceramic particle reinforced Al matrix composites. Parkash et al. [11] investigated the compressive characteristics of Al/SiCp composite foams and found that the localized deformation took place due to the existence of SiCp in cell wall. Gui et al. [12,13] found that A356/SiCp composite foams exhibited a typical brittle characteristic and had better damping and sound absorption properties than Al foams because of the existence of Al/SiCp interfaces. Zn and Zn alloy foams possess excellent mechanical behaviors and damping properties at room temperature [14–16]. However, the work on closed-cell Zn foams prepared with the direct foaming method of melt, to date, is few, and the study on Zn matrix composite foams has not been reported yet. Consequently, it is necessary to investigate various characters (especially functional properties) of Zn and Zn matrix composite foams in order to widen the applying field of metallic foams.
326
S. Yu et al. / Materials Science and Engineering A 457 (2007) 325–328
The purpose of this work is to study the compressive behavior and damping property of ZA22/SiCp composite foams and reveal their mechanisms. 2. Experimental 2.1. Raw materials The raw materials for preparing composite foams included ZA22 alloy (22.0 wt.%Al, 1.0 wt.%Cu, 0.03 wt.%Mg, and Zn balance), ZA22 alloy powders (about 40 m in size), SiC particles (98.0 wt.% in purity, about 28 m in size), and CaCO3 powders (99.5 wt.% in purity, about 44 m in size). SiC particles and CaCO3 powders were used as reinforcement and blowing agent, respectively. To improve the wettability between SiCp and ZA22 melt, SiC particles were heat-treated at 930 ◦ C for 6 h and then at 420 ◦ C for 2 h.
Fig. 1. Thermogravimetric analysis curve of CaCO3 powders.
gas bubbles. Finally the composite foams were cooled down in air.
2.2. Measure of decomposition temperature of blowing agent
2.4. Characterization of composite foams The decomposition reaction of CaCO3 blowing agent can be written as [19]: CaCO3(s) = CaO(s) + CO2(g)
(1)
In order to determine reasonable foaming temperature of ZA22 melt, the decomposition temperature of CaCO3 blowing agent has to be measured. So, CaCO3 blowing agent was studied with Thermogravimetric Analysis (Model DTA/TGRigaku-8150, Japan) under a protection of high pure argon. The heating rate was 20 ◦ C/min. 2.3. Fabrication of composite foams In order to make SiCp and CaCO3 powders enter ZA22 melt easily, powder preforms containing SiCp , ZA22 alloy powders, and CaCO3 powders (the mass ratio is 4:4:1) were prepared. Firstly these powders were blended for 5 h using a ball mill in a stainless steel container. Then the powder mixture was mechanically pressed into a cylindrical die at 20 MPa. The size of the compact preform is Ø 22 mm × 20 mm. Finally cylindrical preforms were baked at 150 ◦ C for 3 h in a vacuum drying oven to remove moisture. According to the thermogravimetric analysis curve of CaCO3 powders (Fig. 1), the beginning temperature of CO2 evolution is about 650 ◦ C. Therefore, when performs were added to ZA22 melt, the temperature of ZA22 melt cannot be more than 650 ◦ C in order to avoid the premature release of CO2 gas. ZA22 alloy was melted to 510 ◦ C in a crucible furnace, and then performs, whose adding amount was determined according to the designed volume fraction (10%) of SiCp in cell wall, were added to the melt. After that, the slurry was stirred for 10 min with a steel stirrer at a rate of 900 r/min to disperse SiC and CaCO3 particles homogeneously and then held at 700–710 ◦ C for 12 min to allow blowing agent to release
Microstructure and phases of the composite foams were analyzed by means of scanning electron microscopy (SEM) (Model JSM-5310, Japan) and X-ray diffraction (XRD) (Model D/Max 2500PC Rigaku, Japan). The porosities of composite foams were calculated using the following equation: ρ∗ P = 1− × 100% (2) ρs where P is the porosity of composite foams, ρ* and ρs are the densities of composite foams and the cell wall material, respectively, and ρ* /ρs , which is called the relative density of composite foams, indicates the ratio of the density of composite foams to the density of cell wall material. 2.5. Compression and damping test Specimens with the dimensions of 15 mm × 15 mm × 30 mm (used for compression test) and Ø 70 mm × 10 mm (used for damping test) were prepared with a wire cutting machine. The size of compressive specimens was chosen to guarantee at least six cells in each direction because samples with smaller dimension can cause a significant loss of mechanical properties [17]. The compressive tests were carried out on a universal mechanical testing machine at a nominal strain rate of 2.2 × 10−3 s−1 . The damping characteristic values were measured using free vibration method. The signal frequency was 400 Hz. The logarithmic decrement δ was used to describe the damping capacity of materials. δ is expressed as [18]: δ = ln
xn xn+1
where xn and xn+1 are amplitudes of successive cycles.
(3)
S. Yu et al. / Materials Science and Engineering A 457 (2007) 325–328
Fig. 2. Photographs of ZA22/10 vol.%SiCp composite foams: (a) optical photograph and (b) SEM photograph of cell wall.
327
Fig. 4. Compressive stress–strain curves of the ZA22 foams (a) and composite foams (b).
3. Results and discussion The microstructures of composite foam are shown in Fig. 2. It can be found that the structure of cells is uniform (Fig. 2(a)) and about 10 vol.% SiCp uniformly distribute in the cell wall of composite foams (Fig. 2(b)). The porosities of composite foams are from 80% to 93%. The XRD pattern of composite foams is shown in Fig. 3. It is clear that Al-rich phase, Zn-rich phase, and SiC exist in the composite foams.
Fig. 3. XRD pattern of ZA22/SiCp composite foams.
3.1. Compressive behaviors of the foams The compressive stress–strain curves of ZA22 foams and composite foams are shown in Fig. 4. It can be found that the stress–strain behaviors of different foams are very similar, which include three distinct regions, i.e., elastic region, plateau region, and densification region. ZA22 foams exhibited typical characteristics of plastic foams. Stress increased linearly with increasing strain in elastic deformation region. Then a long plateau of plastic deformation with slight stress fluctuation generated, during which cell walls buckled and collapsed. The plateau stress increased with increasing relative density (ρ* /ρs ). In densification region, the stress abruptly rose because cell walls contacted each other. Mechanical response of composite foams is more complex than that of ZA22 foams due to the introduction of ceramic particles. The width of plateau region was nearly as much as that of ZA22 foams. But the curves continually fluctuated with increasing strain, and the stress peak appeared time and again (Fig. 4(b)). The main reason is that SiCp in cell walls changed the deformation mechanism of cell walls. The stress concentration took place at SiCp /ZA22 alloy interface during compression test of composite foams. The magnitude of the stress concentration is different at different time and position, which resulted in the localized yielding of composite foams under compressive stress.
328
S. Yu et al. / Materials Science and Engineering A 457 (2007) 325–328
(2) The compressive stress–strain curves of ZA22 foams and composite foams have obvious elastics region, plateau region and densification region. The plateau stress of ZA22 foams increases with increasing relative density. The plateau stress of ZA22/SiCp composite foams fluctuates acutely because SiCp in cell walls alters the deformation mechanism of ZA22 alloy matrix. (3) The damping capacity of closed-cell ZA22 foams is slightly higher than that of ZA22 alloy. Whereas the damping properties of ZA22/SiCp composite foams are obviously higher than those of ZA22 alloy and ZA22 foams. The addition of SiCp can improve the damping capacity of ZA22 foams. Acknowledgements Fig. 5. Damping capacities of different materials. A: ZA22 alloy; B: ZA22 foams (ρ* /ρs = 0.168); C: ZA22 foams (ρ* /ρs = 0.161); D: ZA22/SiCp composite foams (ρ* /ρs = 0.215); E: ZA22/SiCp composite foams (ρ* /ρs = 0.192).
This work was supported by “Program for New Century Excellent Talents in University” and “985 project” of Jilin University of P.R. China.
The results mentioned above are very similar to those of Al matrix composite foams [11].
References
3.2. Damping properties The damping capacities of ZA22 alloy, ZA22 foams and ZA22/SiCp composite foams are given in Fig. 5. ZA22 alloy (A in Fig. 5) has high damping capacity. The damping mechanism of this kind of Zn–Al eutectoid alloy is known to arise from the phase boundary between soft Al-rich phase and rigid Znrich phase [20,21]. The damping properties of closed-cell ZA22 foams (B and C in Fig. 5) are slightly higher than that of ZA22 alloy. This is owing to a mass of macroscopic pores existing in ZA22 foams. The conversions of the stress mode took place in pore boundaries, and the stress concentration generated, which made pores expand and distort and resulted in the reduction of the vibration [22]. In addition, damping capacity could be also obtained by the friction between the crack surfaces of closedcell foams produced in high temperature [23]. The logarithmic decrements of the composite foams (D and E in Fig. 5) were obviously higher than those of ZA22 alloy and ZA22 foams. The main reason is that there were multifarious interfaces and high-density dislocations in composite foams owing to the introduction of SiCp , which resulted in the dislocation damping and interface damping. 4. Conclusions (1) ZA22/10 vol.%SiCp composite foams with porosities from 80% to 93% were fabricated by means of melt foaming route using CaCO3 blowing agent.
[1] J. Banhart, Prog. Mater. Sci. 46 (2001) 559. [2] J. Gibson, M.F. Ashby, Cellular Solids: Structure and Properties, Cambridge University Press, Cambridge, 1997. [3] H.P. Degischer, Handbook of Cellular Metals, Wiley/VCH Gerlag GmbH, 2002. [4] B. Jiang, N.Q. Zhao, C.S. Shi, et al., Mater. Lett. 59 (2005) 3333–3336. [5] V. Gergely, T.W. Clyne, Adv. Eng. Mater. 2 (2000) 175. [6] V. Gergely, D.C. Curran, T.W. Clyne, Comp. Sci. Technol. 63 (2003) 2301–2310. [7] S.W. Ip, Y. Wang, J.M. Toguri, Can. Met. Quart. 38 (1999) 81–92. [8] Y.Q. Sun, T. Gao, Metall. Trans. 33A (2002) 3285– 3292. [9] Kaptay, Colloids Surf. A: Physicochem. Eng. Aspects 230 (2004) 67– 80. [10] Y. Sigimura, J. Meyer, M.Y. He, et al., Acta Mater. 45 (1999) 5245– 5259. [11] O. Parkash, H. Sang, J.D. Embury, Mater. Sci. Eng. A 199 (1995) 195–203. [12] M.C. Gui, D.B. Wang, J.J. Wu, et al., Mater. Sci. Eng. A 286 (2000) 282–288. [13] J. Wu, C. Li, D. Wang, M. Gui, Comp. Sci. Technol. 63 (2003) 569– 574. [14] P.H. Thornton, C.L. Magee, Metall. Trans. 6A (1975) 1801–1807. [15] J. Kov´ae` ik, F. Siman`e´ık, Kovov´e Materi´aly 42 (2004) 70–90. [16] J.N. Wei, Z.B. Li, F.S. Han, Phys Status Solidi A 191 (2002) 435–444. [17] E. Andrews, G. Gioux, P. Onck, J. Gibson, Int. J. Mech. Sci. 43 (2001) 701–714. [18] D.P. Dai, Technical Application of Damping Technology, Tsinghua University Press, Beijing, 1991. [19] M.W.J. Chase, NIST-JANAF Thermochemical Tables, American Chemical Society/American Institute of Physics, Gaithersburg, MD, USA, 1998. [20] I.G. Ritchie, Z.L. Pan, F.E. Goodman, Metall. Trans. 22A (1991) 617– 622. [21] K. Nuttall, J. Inst. Met. 99 (1971) 266–270. [22] J. Zhang, M.N. Gungor, E.J. Lavernia, J. Mater. Sci. 28 (1993) 1515. [23] B. Zettl, S. Stanzl-Tschegg, Materwiss. Werkstofftechn. 4 (2000) 210–214.