Microstructure and mechanical properties of micro-sic p particles reinforced magnesium matrix composites with semi-solid stir casting method

Transcription

1 Microstructure and mechanical properties of micro-sic p particles reinforced magnesium matrix composites with semi-solid stir casting method E. I. Bhiftime, and J. B. Belo Citation: AIP Conference Proceedings 1788, (2017); View online: View Table of Contents: Published by the American Institute of Physics Articles you may be interested in Effect of wt.% SiC p and TiB on the mechanical properties in SiC p /AZ81A magnesium matrix composite by the method semi solid stir casting AIP Conference Proceedings 1788, (2017); / Gear distortion analysis due to heat treatment process AIP Conference Proceedings 1788, (2017); / Combination of ternary Fe 3 O 4 /TiO 2 /CuO nanocomposites and nanographene platelets: High performance photo and sonocatalysis AIP Conference Proceedings 1788, (2017); / Study the effect of active carbon modified using HNO 3 for carbon electrodes in capacitive deionization system AIP Conference Proceedings 1788, (2017); / The effect of thermal cycles during aluminum casting on the intermetallic layer formation at the interface of steel crucible AIP Conference Proceedings 1788, (2017); / Numerical study of 3D brine flow across ice can to analyze heat transfer characteristics AIP Conference Proceedings 1788, (2017); /

2 Microstructure and Mechanical Properties of Micro-SiC p Particles Reinforced Magnesium Matrix Composites with Semi-solid Stir Casting Method E.I. Bhiftime 1, a) 2, b), J.B. Belo 1 Department of Mechanical Engineering, Cenderawasih University, Street Kamwolker, Jayapura 99351, Papua Indonesia 2 Department of Mechanical Engineering, Dili Institute of Technology, Street Ai-mutin, Dili 55718, East Timor a) Corresponding author: irianto.bhiftime@yahoo.com b) boscobelo74@gmail.com Abstract. Metal matrix composites (MMCs) reinforced with ceramics offer high mechanical and good physical properties as compared with corresponding monolithic alloy. MMCs reinforced with SiCp particles in the semi-solid stir casting method was the most simple way. The purpose of the study was to investigate the difference of the microstructure and mechanical properties of SiCp particles reinforced magnesium matrix composites, as well as the changing effects on the extra level of SiCp and TiB, as well as the changing effects on the extra level of SiCp and TiB. The composites used were AZ81A Mg alloy as the matrix and SiCp as the reinforcement (3, 6, 9 wt%). The casting method used in the study was the semi-solid stir casting. The mechanical properties of the composites fabricated by different parameters indicated that semi-solid method resulted improved in nonhomogeneous particle distribution 3 9 wt.% SiCp/AZ81A composites were fabricated by the novel processing. The particle distribution was uniform in these composites. Grain sizes of composites will be much smoother by giving TiB. The ultimate tensile strength, yield strength, and elastic modulus were enhanced as the particle contents increased. The morphology of the composite between the reinforcing SiCp particle and the AZ81A matrix was to be able to unite and to be dispersed evenly. Specimens were tested focusing on the tensile strength, yield strength microstructure and SEM. INTRODUCTION Magnesium matrix composites have become of great interest in the lightweight fields because of their high specific stiffness and high specific strength [1 3]. However, magnesium matrix composites are limitedly used due to their high cost. Their high cost usually comes from three aspects: reinforcements, fabrication processing, and secondary deformation. Thus, economical particles and high efficient production methods should be developed. Micro particles are very economical because of their low prices and easy dispersion during fabrication. The micro particle reinforced Mg matrix composites own the potential commercial use for its relatively low cost and good mechanical properties. Micro particle reinforced metal matrix material is usually produced by powder metallurgy [4,5], high-energy ball milling [6], sputtering [7] and stir casting [8 10], etc. Among all of these methods, stir casting is regarded as the most productive and economical. However, long stir time is necessary to obtain uniform particle distribution. This often results in too much gas and oxidation to Mg matrix. Thus, it is a need to reduce the stirring time to fabricate high-quality composites [11]. Producing different kinds of magnesium alloys through adding Al, Zn, Mn, Ca and other elements is considered as a conventional approach to improving the room temperature mechanical properties. However, recent researchers show that adding reinforcement particles to the magnesium matrices can be more influential in enhancing the mechanical properties compared to the conventional alloying strategies. In this regard, numerous studies have been conducted to characterize the effects of discontinuous particles on the microstructure and subsequent mechanical International Conference on Engineering, Science and Nanotechnology 2016 (ICESNANO 2016) AIP Conf. Proc. 1788, ; doi: / Published by AIP Publishing /$

3 properties of magnesium alloys. It was found that the addition of Al 2O 3 and Cu led to a simultaneous improvement of 0.2% yield compressive strength, ultimate compressive strength, and work of fracture of the AZ31B magnesium alloy fabricated by disintegrated melt deposition technique [12]. The effect of different types of nano-sized oxide particles on the microstructure and mechanical properties of elemental magnesium, prepared using a blend-presssinter technique, has been studied by Hassan and Gupta [13]. For metal matrix composites fabricated by stir casting, particles are generally pushed by the solid/liquid interfaces during solidification, which causes particles segregations along grain boundaries [14]. This type particle distribution is called necklace distribution, which is well-documented in metal matrix composites fabricated by stir casting [15]. Particle distribution and clusters can influence recrystallization behavior of matrix [16,17]. Goh et al. [18] also characterized the properties and deformation behavior of Mg Y 2O 3 nano-composites produced by disintegrated melt deposition. Generally, the nanoparticles reinforced composites have been produced using a variety of methods: stir casting [19], disintegrated melt deposition, powder metallurgy, etc. However, stir casting method is preferred to other techniques due to its capability of producing complex shapes at a high production rate and low costs [20]. The purpose of the study was to investigate the difference of the microstructure and mechanical properties of SiC p particles reinforced magnesium matrix composites, as well as the changing effects on the extra level of SiC p and TiB. Specimens were tested focusing on the tensile strength, yield strength, microstructure and SEM. EXPERIMENTAL METHOD Experiment composites Al-Mg-2TiB/SiC p and Al-Mg-4TiB/SiC p is made by using semi-solid methods stir casting. The AZ81A Mg alloy is considered as a matrix. TiB (2 and 4 wt.%) to soften the grains in the matrix. SiC p particles as reinforcement in the matrix AZ81A (Mg alloy). Variation of SiC p is used (3, 6, 9 wt.%). The chemical composition of the materials used in this work is listed in Table 1 whereas Table 2 shows the variations in the composition of the foundry. Materials AZ81A (Mg alloy) AlTiB (ingot) SiC p (powder) TABLE 1. Chemical composition of materials Chemical composition (%) Al Si SiCp Fe Ti B Mg Mn Zn Other Balance TABLE 2. Variations in the composition of foundry Composition (wt.%) AZ81A AlTiB SiCp (gram) (gram) (gram) Al-Mg-2TiB/SiC p 0% Al-Mg-2TiB/SiC p 3% Al-Mg-2TiB/SiC p 6% Al-Mg-2TiB/SiC p 9% Al-Mg-4TiB/SiC p 0% Al-Mg-4TiB/SiC p 3% Al-Mg-4TiB/SiC p 6% Al-Mg-4TiB/SiC p 9% Total (gram) First, the process to prepare the materials that will be melted is AZ81A and AlTiB. The materials are cut with machines suitable casting composition variation. Then the material is weighed to obtain the composition wt.% which has been set. Casting composition variation can be seen in Table 2. Then AZ81A and AlTiB put in an electric furnace. The following Figure 1(a) is electric furnace

4 (a) FIGURE 1. (a) Electric furnaces stir casting, Temperature vs time semi-solid stir casting process And then it is heated to up temperatures of 800 C to obtain a liquid condition. Then the temperature was lowered to 590 C to obtain semi-solid condition. Meanwhile, SiC p particles and borax are heated in a separate place in the open electricity at a temperature of 400 C for 1200 seconds. Furthermore, SiC p and borax are included in an electric furnace and then stirred thoroughly using a mechanical stirrer. Rotational speed stirrer is 500 rpm for 180 seconds. The metal mold is also heated to a temperature of 300 C. Once everything is mixed and stirred in a state of semisolid, then the temperature is increased to temperatures of 750 C to obtain casting conditions. Results casting is cooled at room temperature 36 C. Figure 1 shows the semi-solid graph of temperature vs time. After that, composites was cut to fit the test specimen. Composite specimens were tested for the use of tensile strength, yield strength, microstructure and SEM. RESULTS AND DISCUSSIONS Density and Porosity The specimen of density test had the size of 2.5 cm x 2.5 cm x 2.5 cm by using a digital balance VIBRA. The density test and its measurement of porosity of composite Al-Mg-2TiB/SiC p and Al-Mg-4TiB/SiC p were shown in Table 3. TABLE 3. Test results in density and porosity calculations Composites (wt.%) Mdry Mwet ρactual (g/cm 3 ) ρtheoretic (g/cm 3 ) Porosity Al-Mg-2TiB/SiC p 0% Al-Mg-2TiB/SiC p 3% Al-Mg-2TiB/SiC p 6% Al-Mg-2TiB/SiC p 9% Al-Mg-2TiB/SiC p 0% Al-Mg-2TiB/SiC p 3% Al-Mg-2TiB/SiC p 6% Al-Mg-2TiB/SiC p 9% The graphic of density and porosity of composite Al-Mg-2TiB/SiC p and Al-Mg-4TiB/SiC p was shown in Fig. 3 below:

5 (a) FIGURE 2. Graph of (a) density, the level of porosity composite The density graphic indicated that composite Al-Mg-2TiB/SiC p underwent an increase averagely 1.2%. Whereas, composite Al-Mg-4TiB/SiC p went through a decrease in the variation of SiC p (6 wt.%) and increased as much as 1.4% on the variation of SiC p (9 wt.%). Figure 3 showed that the porosity of composite Al-Mg-2TiB/SiC p increased averagely as much as 28%. Whereas, the composite Al-Mg-4TiB/SiC p decreased on the variation of SiC p (6 wt.%) and then, increased as much as 10.9% on the variation of SiC p (9 wt.%). On the process of stir casting, porosity might potentially occur. This occurrence may be caused by the chemical reaction between the matrix and reinforcing particle so that it may result in the trapped gas during the mixing process. Consequently, the more the number of SiC p, the more the gas reaction occurs, the porosity would tend to increase. This result, according to the result from previous researchers, indicated that porosity on the process of stir casting may potentially occur because of the chemical reaction between reinforcing particle and matrix which caused gas, as well as a gas which was trapped during the stirring process [6]. Therefore, Mg would reduce the layer of SiO 2 on the surface of SiC p, and form MgAl 2O 4 on the interface with high wettability [16]. The porosity formed on the interface of the matrix and reinforcing particles would disappear or get reduced [17]. Tensile Test Tensile strength was acquired from the measurement of maximum load divided by the cross-sectional area of the tensile test specimen. The tensile test was conducted according to the testing standard of ASTM E 8M-04 [18]. The following was Table 4. The result of tensile test: TABLE 4. Test results of tensile strength calculations Composites (wt.%) σu (MPa) σy (MPa) %EL Al-Mg-2TiB/SiC p 0% Al-Mg-2TiB/SiC p 3% Al-Mg-2TiB/SiC p 6% Al-Mg-2TiB/SiC p 9% Al-Mg-2TiB/SiC p 0% Al-Mg-2TiB/SiC p 3% Al-Mg-2TiB/SiC p 6% Al-Mg-2TiB/SiC p 9% The effect of percentage SiC p to the tensile strength of composite Al-Mg-2TiB/SiC p and Al-Mg-4TiB/SiC p was shown by Fig

6 (a) (c) FIGURE 3. Graph (a) Tensile strength, Yield strength, (c) Elongation, Al-Mg-2TiB/SiCp dan Al-Mg-4TiB/SiCp Composite As shown in Fig. 3(a), the graphic of the tensile strength of composite Al-Mg-2TiB/SiC p was bigger than composite Al-Mg-4TiB/SiC p with the difference of averagely 16.18%. The strength of composite Al-Mg-4TiB/SiC p increased on the variation of SiC p (3 wt.%) 120 MPa and the variation of SiC p (9 wt.%) became 143 MPa as much as 22.16%. For the composite Al-Mg-2TiB/SiC p the tensile strength increasing was on the variation of SiC p (3 wt.%) MPa, the variation of SiC p (9 wt.%) to be 125 MPa, or as much as 19.01%. The addition of TiB 4% could increase the tensile strength. Fig. 3 indicated that the biggest yield strength was on the composite Al-Mg- 4TiB/SiC p that was as much as 106 MPa. The difference on the yield strength on the composite Al-Mg-2TiB/SiC p and Al-Mg-4TiB/SiC p was as much as 14 MPa. The yield strength on the composite Al-Mg-4TiB/SiC p was bigger than on the composite with matrix Al-Mg-2TiB/SiC p. It could be concluded from Fig. 3(c) that the strain between composite Al-Mg-2TiB/SiC p and Al-Mg-4TiB/SiC p increased with the difference as much as 0.55 %EL. The strain on the composite Al-Mg-2TiB/SiC p was averagely 1.56 %EL. Whereas, the strain on the composite Al-Mg- 4TiB/SiC p was averagely 2.11 %EL. The amount of force on the composite Al-Mg-4TiB/SiC p was bigger than on the composite Al-Mg-2TiB/SiC p. It was based on what previous researchers discovered that the extra level of TiB with certain percentage would repair the grain structure on the composite [10,19]. Microstructure The microstructure testing by using Olympus, an optical microscope with a magnification Al-Mg of 100X, produced photos structure micro of Al-Mg-2TiB/SiC p and Al-Mg-4TiB/SiC p in Fig. 4 and 5 below

7 (a) (c) (d) FIGURE 4. Micro composite Al-Mg-2TiB/SiCp (a) 0% SiCp 3% SiCp (c) 6% SiCp (d) 9% SiCp Figure 4 is the composite Al-Mg-2TiB/SiCp whereas, a part of the matrix that was black were increasingly fine grain boundaries. Then, Figure 5 indicated that the composite Al-Mg-4TiB/SiCp with black color was on the fine grain boundaries. It shows that TiB produces grains on that composite. The more SiCp dispersed, the harder it may become. (a)

8 (c) (d) FIGURE 5. Micro composite Al-Mg-4TiB/SiCp (a) 0% SiCp 3% SiCp (c) 6% SiCp (d) 9% SiCp (a) (c) FIGURE 6. The morphology of composites Al-Mg-2TiB/SiCp 9%

9 (a) (c) FIGURE 7. The morphology of composites Al-Mg-4TiB/SiCp 9% (a) FIGURE 8. SEM of composite (a) Al-Mg-2TiB/SiCp 6% Al-Mg-4TiB-SiCp 6% Figure 6, 7 and 8 the morphology of the composites Al-Mg-2TiB/SiC p and Al-Mg-4TiB/SiC p between reinforcing particles and matrix could be fused. In the composite Al-Mg-2TiB/SiC p, there were SiC p particles surrounding the Mg alloy matrix that was mutually binding. Whereas, the composite Al-Mg-4TiB/SiC p, was seen between SiC p and matrix Mg alloy in which they could mix well. Then, with the addition of TiB, it may cause changes in the particle shape to become smoother and spread evenly

10 CONCLUSION In this study to test the tensile strength, yield strength, microstructure test as well as SEM will be obtained several things: The highest tensile strength of the composite Al-Mg-4TiB/SiC p (9 wt.%) Ie 243 MPa. The yield strength of the composite Al-Mg-4TiB/SiC p (9 wt.%) Ie 195 MPa. The microstructure of composite Al-Mg- 2TiB/SiC p agglomeration contained on the surface of the matrix. The enhancement in of 4TiB compounds composite Al-Mg-4TiB/SiC p, SiC p particles spread more evenly. The morphology of SEM test results of composite Al-Mg-2TiB/SiC p and Al-Mg-4TiB/SiC p between reinforcement and matrix particles can be fused and well dispersed. REFERENCES 1. E. Bedolla, J. Lemus-Ruiz and A. Contreras, Mater. Des. 38, 91 8 (2012). 2. M.K. Habibi, S.P. Joshi and M. Gupta, Acta Mater. 58, (2010). 3. X.J. Wang, X.S. Hu, K. Wu, M.Y. Zheng, L. Zhen and Q.J. Zhai, J. Mater. Sci. 44, (2009). 4. S.F. Hassan and M. Gupta, Mater. Sci. Eng. A 392, (2005). 5. H. Abdizadeh, M. Ashuri, P.T. Moghadam, A. Nouribahadory and H.R. Baharvandi, Mater. Des. 32, (2011). 6. L. Lu, K.K. Thong and M. Gupta, Compos. Sci. Technol. 63, (2003). 7. S.F. Hassan and M. Gupta, J. Mater. Sci. 37, (2002). 8. S.J. Wang, G.Q. Wu, Z.H. Ling and Z. Huang, Mater. Sci. Eng. A 518, (2009). 9. Y. Cai, M.J. Tan, G.J. Shen and H.Q. Su, Mater. Sci. Eng. A 282, (2000). 10. S.A. Sajjadi, H.R. Ezatpour and M. Torabi Parizi, Mater. Des. 32, (2012). 11. K.B. Nie, X.J. Wang, K. Wu, L. Xu, M.Y. Zheng and X.S. Hu, J. Alloys Compd. 509, (2011). 12. Q.B. Nguyen and M. Gupta, J. Alloys Compd. 459, (2008). 13. S.F. Hassan and M. Gupta, J. Alloys Compd. 419, (2006). 14. Y.L. Liu, N. Hansen and D. Juul. Jensen, Metall. Trans. A 20, (1989). 15. D.J. Lloyd, Int. Mater. Rev. 39(1), 1 23 (1994). 16. C.S. Goh, J. Wei, L.C. Lee and M. Gupta, Acta Mater. 55, (2007). 17. A. Mazahery, H. Abdizadeh and H.R. Baharvandi, Mater. Sci Eng. A 518, 61 4 (2009). 18. A.A. Yar, M. Montazerian, H. Abdizadeh and H.R. Baharvandi, J. Alloys Compd. 484, (2009). 19. Y. Prasad, K.P. Rao and M. Gupta, Compos. Sci. Technol. 69, (2009). 20. Q.B. Nguyen and M. Gupta, J. Alloys Compd. 459, (2008)