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Investigation of Micro-structure and Mechanical Behaviour of Aluminum - Zircon Sand - Tungsten Carbide Metal Matrix Composites
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ScienceDirect Materials Today: Proceedings 5 (2018) 25553–25561
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IConAMMA_2017
Investigation of Micro-structure and Mechanical Behaviour of Aluminum - Zircon Sand - Tungsten Carbide Metal Matrix Composites B. Vijaya Ramnath1*, J. Jeykrishnan2, S. Akilesh3, B. Saravanan3, V. Krishna Vivek3 1
Professor, 2Asst. Professor, Department of Mechanical Engineering, Sri Sai Ram Engineering College, Chennai 600044, India 3 Students, Department of Mechanical Engineering, Sri Sai Ram Engineering College, Chennai 600044, India
Abstract Nowadays composites play a vital role in automotive and aircraft applications. The main objective of this work is to employ aluminum-zircon sand – tungsten carbide metal matrix composites as they possess light in weight characteristics with improved corrosion and hardness properties. The casting was made up with stir casting and the mechanical properties are studied. This paper deals with the investigation of effects of zircon sand and tungsten carbide as reinforcements in aluminum metal matrix composite. The results show that tensile strength of composite increases with increase in percentage of tungsten carbide from 0.5 % to 1.5 %. But, when it is 2% there is reduction in strength due to higher content of tungsten carbide. Similar to tensile test results, compressive load also increases up to 1.5%. The impact test reveals that the energy absorbed by all the composites is similar to each other. The hardness test proves that the hardness of the alloy decreases with increase in the alloying content. Morphological analysis is carried out to find the internal structure of the tested specimens. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017]. Keywords: Metal matrix composite; Aluminum; Zircon sand; Tungsten carbide; Stir casting; Mechanical characteristics
1. Introduction Metal matrix composites (MMC) are being mostly used in many applications because of their advanced properties in automotive industry and also for aircraft applications, since last two decades. It’s because of the improved mechanical properties like good strength, light weight, less density and good corrosion resistance, the aluminum MMC are considered to be one of the best in the composite fraternity [1]. After iron, aluminum (Al) is the 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017].
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most widely employed material in the industries citing good mechanical properties such as good corrosion resistance, less in density, excellent thermal conductivity etc. It has a good Young’s modulus and hardness. Its melting point is 660°C. The strength of the aluminum decreases, when the temperature increases but the MMC gets more toughened, strengthened when an aluminum has been added with the reinforcing materials like silicon carbide (SiC), zircon sand, tungsten carbide (WC), aluminum oxide, (Al2O3), boron carbide (B4C) etc. The characteristics of the aluminum alloy have been drastically improved as they have been reinforced with the materials like TiB2 particles [2]. Many techniques like stir casting and pressure casting are used in the industry to manufacture many metal matrix composites depending on their reinforcement particles [3]. Tribological and mechanical properties of the metal matrix composites can improve by incorporation of reinforcement particles in the nanometer range [4]. Uniform particle distribution in the radial and axial directions must be the important parameters carried out during the formation of MMC. Large porosity is produced due to the entrapment of gas during stir casting while melting [5]. When the size of the particles and weight percentage gets increased the density of the composites get increases however decreasing the size and weight percentage of particles can increase the porosity of the composites [6]. Jenix et al [7] have compared with four different volume fractions for Al6063 with alumina and zircon sand and found that the composites had higher hardness and tensile strength for (4+4) % combination. Abrasive wear for the Al-Cu alloy with alumina and zircon sand particles was studied by Das et al [8] and they have come to a conclusion that zircon reinforced Al MMCs has better abrasive wear than that of the alumina reinforcement. Fabian et al [9] have developed a MMC by reinforcing tungsten carbide (WC) particles with different weight proportions and have concluded that there is a significant increase in the mechanical properties of the MMC. The mechanical properties such as hardness and tensile strength are significantly increased by the addition of WC reinforcement in the matrix material and they have concluded that the wear resistance of the composite material increases with the increase in WC contents [10 & 11]. Jeykrishnan et al [12] has manufactured aluminum base SiC MMC using stir casting method and have concluded that the mechanical characteristics such as tensile strength and impact properties improves on the addition on SiC particles. Karthik et al [13] have fabricated aluminum MMC by reinforcing TiB2 particles by varying its proportion using stir casting technique and have reported that the tensile strength, impact and hardness values have shown improvement while adding the reinforcement particles. Ravikumar et al [14] have manufactured Al MMC by adding tungsten carbide (WC) particles by varying percentages such as 2%, 4%, 6%, 8% and 10% by weight and investigated the mechanical properties of the composites and have reported that the impact strength and elongation has decreases on adding WC reinforcements. Vijaya Ramnath et al [15] have reported that the MMC fabricated using alumina and boron carbide particles have better mechanical properties such as hardness, impact strength than the un-reinforced aluminum alloy. Baradeswaran et al [16] have fabricated Al7075 MMC by reinforcing B4C particles and have reported that on adding the reinforcements the wear resistance of the material increases and co-efficient of friction of the material decreases. Vijaya Ramnath et al [17, 18] have prepared Al MMC by adding carbon nano-tube (CNT) particles and have concluded that no considerable improvement in hardness properties on adding the CNT particles but a considerable increase in the compressive strength of the material. It has been found that the composites are mostly prepared by the stir casting method and no or little work has been done on reinforcing WC as well as zircon sand with varying proportions to manufacture MMC, which has wide applications in aerospace and automobile industries. 2. Materials and manufacturing 2.1 Materials Aluminum (Al6061) alloy with a density of 2.65g/cm3 has been employed as a matrix material in MMC, as it is well known that Al has good mechanical and thermal properties and finds good applications in marine and aerospace industries. The composition of Al6061 has been given in table 1. In this work for preparing metal–matrix composite, zircon sand and tungsten carbide (WC) in powder form have been used as the reinforcements. WC has a density of 15.63 g/cm³ and a melting point of 2,870 °C. WC is one of the most promising ceramic materials due to its attractive properties, including high strength, density double of that of steel, high melting point of 2870 °C. It has a hexagonal crystal structure and a specific heat capacity of 39.8 J/ (mol·K).
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Table 1. Composition of Al6061 Si
Mg
Fe
Cu
Zn
Cr
Al
0.6
1.0
0.7
0.25
0.25
0.3
Bal
2.2. Manufacturing procedure and results Al silicon alloy bar is cut into small pieces of 10 cm x 3cm x 5cm in dimensions, so that it can be easily placed in the crucible for melting. Al 11.6% silicon alloy has a nominal composition of 10.5% to 13.5% Silicon, 0.05% of lead, tin, chromium, magnesium, nickel each, 0.1% each of titanium and zinc, 0.35% of manganese, 0.4% of iron and 0.03% of copper. The alloy has been theoretically said to have slightly more tensile, compressive and impact strength when compared to pure Al. Zircon sand is a chemical compound which is used in steel foundry, refractory, ceramics and weld fluxes. It is uniform in size and has excellent heat transfer coefficient. Due to its hardness, durability and chemical inertness, zircon persists in sedimentary deposits and is a common constituent of most sands. Stir casting is a primary process of composite production in which continuous stirring of molten metal is done followed by introduction of reinforcements. The resulting mixture is then poured into the die and allowed to solidify. In stir-casting, the particles often tend to form agglomerates, which can be only dissolved by vigorous stirring at high temperature. The advantages of stir castings are simplicity, flexibility, applicability to large quantity, near net shaping, lower cost of processing and easier control of matrix structure. In this work, stir-casting is used for preparing Al metal–matrix composite. This whirlpool technique provides high strength and homogeneous set of Al composite materials. Table 2. Composition of Composites Sample no 1.1
Composite 1 Al 11.6% Si alloy + tungsten carbide 0.5%
1.2
Al 11.6% Si alloy + tungsten carbide 1%
1.3
Al 11.6% Si alloy + tungsten carbide 1.5%
1.4
Al 11.6% Si alloy + tungsten carbide 2%
Sample no 2.1
Composite 2 Al 11.6% Si alloy + zircon sand 0.5%
2.2
Al 11.6% Si alloy + zircon sand 1%
2.3
Al 11.6% Si alloy + zircon sand 1.5%
2.4
Al 11.6% Si alloy + zircon sand 2%
Sample no
Composite 3
3.1
Al 11.6% Si alloy + tungsten carbide 0.5% + zircon sand 0.5%
3.2
Al 11.6% Si alloy + tungsten carbide 1% + zircon sand 1%
3.3
Al 11.6% Si alloy + tungsten carbide 1.5% + zircon sand 1.5%
3.4
Al 11.6% Si alloy + tungsten carbide 2% + zircon sand 2%
In this work, three types of composites namely composite 1, composite 2 and composite 3 have been fabricated. In each composite, four samples have been prepared. Their details were shown in table 2. The experimental arrangement consists of the main furnace and components along with four mild steel stirrer blades. The primary process in the experiment is preheating. Here, the empty crucible and the reinforcement powders, namely WC and zircon sand powders have been heated separately to a temperature close to that of the main process temperature. The melting of the Al alloy has been carried out in the graphite crucible inside the furnace. Initially, the ingot was preheated for 1 hour at 550 °C. Then, the crucible with Al alloy is heated to 840 °C while the preheated powders are mechanically mixed with each other below their melting points. This metal matrix is then kept into the furnace at the
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same temperature. The furnace completely melts the pieces of Al alloy and the preheated zircon sand and WC. Now, stirring mechanism is lowered into the crucible inside the furnace and set at the required depth. The vigorous automatic stirring of the material takes place for 10 min with 600 rpm stir ingrate, thereby uniformly dispersing the additive powders in the Al alloy matrix. The temperature rate of the furnace should be controlled at 840 ±10 °C in the mixing process. The degasser removes all the trapped gases in the crucible and ensures that the temperature of the mixture does not get transferred easily to the atmosphere. This experiment is repeatedly done by varying the compositions of the composite powder for producing different types of composites. Mechanical testing is needed to evaluate the radical properties of materials as well as in developing new composite materials and to control the quality of materials used in design. The ability of a material to withstand a static load can be determined by testing the material in tension or in compression in an universal testing machine (UTM) where the specimen has been prepared as per B-557M standard. The use of compression test is to determine the compression property of composite. The specimen is prepared as per ASTM E8 standard. Impact testing involves the sudden and dynamic application of the load on the composite specimen. This test measures the amount of energy absorbed by the specimen during rupture in joules. The specimen is prepared as per IS 1757 standard. The hardness test measures the resistance offered by a material against the force applied. Brinell hardness test was carried out in this work to determine the deformation of the composite under constant compressive load. The results obtained for tensile test have been furnished in table 3. Also, the results of tensile test are represented in fig 1, 2 and 3 for composite 1, 2 and 3 respectively. From the fig 3, it has been observed that the sample 1.3 shows better tensile strength at 172.02 MPa which is due to the presence of 1.5 % of WC particles. Also, it has been observed that the tensile strength of sample 1.4 is reduced to 82.08 MPa which is the result of increase in the content of WC beyond certain percentage. Hence, it has been concluded that addition of WC particles above 1.5 % reduces the tensile property of the composite. The samples of tensile and compressive strength tests have been prepared as per ASTM E8 standards. Table 3. Result of Tensile Test Name of Composite
1
2
3
Sample no
Tensile strength (MPa)
Yield stress (MPa)
Elongation %
1.1
102.8
91.05
3.54
1.2
146.5
131.11
2.44
1.3
172.2
150.59
3.26
1.4
82.8
73.36
1.96
2.1
105.8
96.06
1.94
2.2
133.9
118.48
2.36
2.3
97.6
89.14
2.34
2.4
97.2
89.14
2.34
3.1
177.4
155.90
2.52
3.2
134.2
120.49
2.36
3.3
140.5
97.03
1.74
3.4
111.7
116.37
1.44
From fig 2 it has been noted that sample 2.2 shows better mechanical behaviour at 133.9 MPa which is due to the presence of 1% zircon sand with aluminium alloy. Since Zr content increases to 1.5%, the mechanical strength (tensile strength) starts decreasing which is due to the result of increase in brittleness of the composite. From fig 3, it is observed that sample 3.1 has mechanical strength of 177.4 MPa which is higher than all the composites fabricated in this work. This is due to the presence of equal amount of WC and Zr of 0.5% each. It is noted that the increase of reinforcement reduces the tensile strength of composites. This is due to increase in hardness of composite by addition of reinforcement and has good agreement with [14]. Hence, it is concluded that 0.5% addition of WC and 0.5% of Zr is a better combination for having good mechanical strength. The compressive strength properties have been furnished in table 4. It has been observed that the sample 3.3 shows the highest compressive load value of 117.55 kN.
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The energy absorbed by all the 12 samples is furnished in table 5. It is found that the impact load or energy absorbed by all the 12 samples is 2 joules. No variation is found in the impact load. Brinell hardness test is used for testing the sample material and it is carried out on all the samples of various compositions of materials. The results are furnished in the table 6. Ball indenter made of hardened steel is used for the test. The diameter of the ball indenter is 10 mm and the applied load is 500 kg/mm2. The samples have been prepared as per the ASTM E10-00 standards. Table 6 shows the hardness values of all the composites.
Fig. 1. Tensile behavior of composite 1
Fig. 2. Tensile behavior of composite 2
Fig. 3. Tensile behavior of composite 3 Table 4. Result of compression test
Name of Composite
1
2
3
Sample no
Compressive load (kN)
1.1 1.2 1.3 1.4 2.1 2.2 2.3 2.4 3.1 3.2 3.3 3.4
88.33 100.91 113.74 87.02 82.90 96.57 106.98 92.04 96.12 108.92 117.55 94.94
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B. Vijaya Ramnath/ Materials Today: Proceedings 5 (2018) 25553–25561 Table 5. Result of Impact Test Name of composite 1
2
3
Sample No 1.1 1.2 1.3 1.4 2.1 2.2 2.3 2.4 3.1 3.2 3.3 3.4
Impact Load (Joules) 2.5 2.3 2.1 1.8 3.4 3.3 3.1 2.8 4.3 4.2 3.9 3.7
The energy absorbed by all the 12 samples is furnished in table 5. It is found that the impact load or energy absorbed by samples decreases as the inclusion of reinforcement particles decreases the hardness of the samples and they are in line with [14]. Brinell hardness test is used for testing the sample material and it is carried out on all the samples of various compositions of materials. The results are furnished in the table 6. Ball indenter made of hardened steel is used for the test. The diameter of the ball indenter is 10 mm and the applied load is 500 kg/mm2. Table 6 shows the hardness values of all the composites. The samples of impact tests have been prepared as per IS 1757 standards.
Table 6. Result of Hardness Test Name of Composite
1
2
3
Sample no
Diameter of indentation (mm)
Hardness (BHN)
1.1
2.9
74.1
1.2
2.9
68.1
1.3
3.1
64.6
1.4
3.3
56.8
2.1
3.1
76.6
2.2
3.1
69.6
2.3
3.1
63.6
2.4
3.2
60.5
3.1
2.8
79.6
3.2
3
69.1
3.3
3
60.1
3.4
3.4
53.4
The hardness of the 4 different samples has been observed. The hardness decreases with the increase in the amount of tungsten carbide, zircon sand or both. The main inference made is that the hardness decreases with the presence of these powders in the metal matrix. Fig. 5 shows the SEM image of the fractured surface of tensile test of sample 1 at 100x magnification and the microscope used in the experiment is SUPRA 520. The general arrangement of aluminum molecules and reinforcements of the aluminum alloy are faintly visible in the image. The aluminum particles which are elliptically shaped in the matrix are more clearly visible at a magnification of 500x as shown in
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fig.6. It is seen that the reinforcements of the matrix and aluminum molecules are distributed unevenly in the region, suggesting that the even distribution of the matrix and reinforcement is done by increasing in the time of stirring during the manufacturing of the sample. The specimen shows a ductile fracture appearance with shearing effects on the surface.
Fig. 4. Hardness graph for all 3 composites
Completely Al particles
Fig. 5. SEM image of sample 1
WC particles
Fig. 6. SEM image of sample 1
Fig. 7 reveals the fractured surface of the sample 2 after tensile test at 108x magnification. The general arrangement of the composite is clearly visible in the image. Many defects, such as micro cracks, porous sites have been avoided by the better stirring time during manufacturing. However, some typical examples of crack paths on the specimen surface of the composites were seen in the image. However, only a few debonding particles are observed compared to sample 1. Fig. 8 shows the microstructure of sample 3 which consist of Al alloy. The picture shows the inner surface of sample 3 which consist of aluminum and other components like Si, WC, Zr etc. It
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consists of tighter packing than the other composites which explains the better tensile and flexural properties of sample 3 compared to sample 2.
Crack Initiation
Zircon sand particles
Fig. 7. SEM image of sample 2
Fig. 8. SEM image of sample 3
3. Conclusions The hardness of the 4 different samples has been observed. The hardness decreases with the increase in the amount of tungsten carbide, zircon sand or both. The main inference made is that the hardness decreases with the presence of these powders in the metal matrix. In this work, twelve different samples are fabricated and the following inferences are made; (1) It has been inferred that the tensile strength of sample 3.1 has marginally higher than that of other samples because of its more Al particle content with all the other materials of minimum composition used (WC 0.5% and Zr 0.5%) and sample three has the second highest value of tensile strength when compared to other samples (tungsten carbide 1.5%). (2) It has been found that sample 3.3 (tungsten carbide 1.5% and zircon sand 1.5%) has more compressive strength than all the other samples (117.55 kN). (3) It is found that the impact strength decreases on addition of reinforcements. (4) Also, Brinell hardness test for all the 12 samples are noted and the maximum hardness is found to be 79.6 (BHN) for Al 11.6% Si alloy + tungsten carbide 0.5% + zircon sand 0.5% composite. (5) The SEM analysis has been completed on the composite materials and has been showcased. References [1]. Daniel B. Miracle and Steven L. Donaldson, “Introduction to composites”, ASM Handbook of composite materials, Vol. 21. [2]. Tamer Ozben, ErolKilickap, Orhan Çakir, “Investigation of mechanical and machinability properties of SiC particle reinforced Al-MMC”, Journal of materials processing technology, Vol. 198, (2008) 220-225. [3]. B Bobic, S. Mitrovic, M. Babic, I. Bobic, “Corrosion of Metal-Matrix Composites with Aluminium Alloy Substrate”, Tribology in industry, Volume 32, No. 1, 2010. [4]. M. Ramachandra and K. Radhakrishna, “Effect of reinforcement of flyash on sliding wear, slurry erosive wear and corrosive behavior of aluminium matrix composite”, Wear Vol. 262, 2007, 1450-1462. [5] Seo YH, Kang CG, “Effects of hot extrusion through a curved die on the mechanical properties of SiC/Al composites fabricated by melt stirring”, Compos Sci Tech 1999:643-54. [6]. Hosseini N, Karimzadeh F, Abbasi MH, Enayati MH, “Tribological properties of Al6061-Al2O3 nano-composite prepared by milling and hot pressing”, Materials design, Vol. 31, 2010, pp. 4777- 4785.
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[7]. J. Jenix Rino, Dr. D. Sivalingappa, Halesh Koti and V. Daniel Jebin, “Properties of Al6063 MMC reinforced with zicon sand and alumina”, IOSR journal of Mechanical and Civil Engineering, Vol. 5, Issue: 5, 2013, pp. 72-77. [8]. Sanjeev Das, Siddhartha Das and Karabi Das, “Abrasive wear of zircon sand and alumina reinforced Al–4.5 wt% Cu alloy matrix composites – A comparative study”, Composites Science and Technology, Vol. 67, 2007, pp.746. [9]. S. Jerry Andrews Fabian, B. Selvam, “Densification behaviour of Aluminium reinforced with Tungsten Carbide particulate Metal Matrix Composite processed by P/M”, IOSR Journal of Mechanical and Civil Engineering, pp. 24-29. [10]. Amarnath.G, K.V. Sharma, “Microstructure and tribological properties of nano-particulate WC/Al metal matrix composites”, International journal of mechanical engineering and technology, Vol. 4, Issue 2, 2013, pp. 178-188. [11] Hari Prasada Rao Pydi, Balamurugan Adhithan, A.Syed Bava Bakrudeen ,“Microstructure Exploration of the Aluminum-Tungsten Carbide Composite with different Manufacturing circumstances”, International Journal of Soft Computing and Engineering, ISSN: 2231-2307, Vol. 2, Issue: 6, 2013. [12]. J. Jeykrishnan, B. Vijaya Ramnath, X. Hervin Savariraj, R. David Prakash, V. R. Dhinesh Rajan and D. Dinesh Kumar, “Investigation on tensile and impact behavior of aluminum base silicon carbide metal matrix composites”, Indian journal of science and technology, Vol. 9 (37), 2016. [13]. J. Jeykrishnan, S. Jayanthi Nathan and M.R. Karthik, “Fabrication and Characterization of Aluminum Titanium Di-Boride Metal Matrix Composites Using Stir Casting Technique”, International Journal of Mechanical Engineering and Technology, Vol. 8 (4), 2017, pp. 13–18. [14]. K. Ravikumar, K. Kiran, V.S. Sreebalaji, “Characterization of mechanical properties of aluminium/tungsten carbide composites”, Measurement, Vol. 102, 2017, pp. 142-149. [15]. B. Vijaya Ramnath, C. Elanchezhian, M. Jaivignesh, S. Rajesh, C. Parswajinan, A. Siddique Ahmed Ghias, Evaluation of mechanical properties of aluminium alloy– alumina–boron carbide metal matrix composites, Materials and Design, Vol. 58, 2014, pp. 332–338. [16]. Baradeswaran A, Perumal AE, “Influence of B4C particles on the tribological and mechanical properties of Al 7075 – B4C composites”, Composites: Part B, Vol. 54 (1), 2013, pp. 146-152. [17]. B. Vijaya Ramnath, C. Parswajinan, C. Elanchezhian, S. Venkatesan Pragadeesh, C. Kavin, P.R. Ram kishore, V. Sabarish, “Experimental Investigation on Compression and Chemical Properties of Aluminium Nano Composite”, Applied Mechanics and Materials, Vol. 680, 2014, pp. 7-10. [18]. C. Parswajinan, B. Vijaya Ramnath, M. Vetrivel, C. Elanchezhian, K. Loganathan, R. Sarvesh, C. Rohit Prasanna, R.N. Karthick Babu, “Experimental investigation of Mechanical and chemical properties of aluminum reinforced with MWCNT”, Applied Mechanics and Materials, Vol. 766-767, 2015, pp. 28-292.
ScienceDirect Materials Today: Proceedings 5 (2018) 25553–25561
www.materialstoday.com/proceedings
IConAMMA_2017
Investigation of Micro-structure and Mechanical Behaviour of Aluminum - Zircon Sand - Tungsten Carbide Metal Matrix Composites B. Vijaya Ramnath1*, J. Jeykrishnan2, S. Akilesh3, B. Saravanan3, V. Krishna Vivek3 1
Professor, 2Asst. Professor, Department of Mechanical Engineering, Sri Sai Ram Engineering College, Chennai 600044, India 3 Students, Department of Mechanical Engineering, Sri Sai Ram Engineering College, Chennai 600044, India
Abstract Nowadays composites play a vital role in automotive and aircraft applications. The main objective of this work is to employ aluminum-zircon sand – tungsten carbide metal matrix composites as they possess light in weight characteristics with improved corrosion and hardness properties. The casting was made up with stir casting and the mechanical properties are studied. This paper deals with the investigation of effects of zircon sand and tungsten carbide as reinforcements in aluminum metal matrix composite. The results show that tensile strength of composite increases with increase in percentage of tungsten carbide from 0.5 % to 1.5 %. But, when it is 2% there is reduction in strength due to higher content of tungsten carbide. Similar to tensile test results, compressive load also increases up to 1.5%. The impact test reveals that the energy absorbed by all the composites is similar to each other. The hardness test proves that the hardness of the alloy decreases with increase in the alloying content. Morphological analysis is carried out to find the internal structure of the tested specimens. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017]. Keywords: Metal matrix composite; Aluminum; Zircon sand; Tungsten carbide; Stir casting; Mechanical characteristics
1. Introduction Metal matrix composites (MMC) are being mostly used in many applications because of their advanced properties in automotive industry and also for aircraft applications, since last two decades. It’s because of the improved mechanical properties like good strength, light weight, less density and good corrosion resistance, the aluminum MMC are considered to be one of the best in the composite fraternity [1]. After iron, aluminum (Al) is the 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017].
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B. Vijaya Ramnath/ Materials Today: Proceedings 5 (2018) 25553–25561
most widely employed material in the industries citing good mechanical properties such as good corrosion resistance, less in density, excellent thermal conductivity etc. It has a good Young’s modulus and hardness. Its melting point is 660°C. The strength of the aluminum decreases, when the temperature increases but the MMC gets more toughened, strengthened when an aluminum has been added with the reinforcing materials like silicon carbide (SiC), zircon sand, tungsten carbide (WC), aluminum oxide, (Al2O3), boron carbide (B4C) etc. The characteristics of the aluminum alloy have been drastically improved as they have been reinforced with the materials like TiB2 particles [2]. Many techniques like stir casting and pressure casting are used in the industry to manufacture many metal matrix composites depending on their reinforcement particles [3]. Tribological and mechanical properties of the metal matrix composites can improve by incorporation of reinforcement particles in the nanometer range [4]. Uniform particle distribution in the radial and axial directions must be the important parameters carried out during the formation of MMC. Large porosity is produced due to the entrapment of gas during stir casting while melting [5]. When the size of the particles and weight percentage gets increased the density of the composites get increases however decreasing the size and weight percentage of particles can increase the porosity of the composites [6]. Jenix et al [7] have compared with four different volume fractions for Al6063 with alumina and zircon sand and found that the composites had higher hardness and tensile strength for (4+4) % combination. Abrasive wear for the Al-Cu alloy with alumina and zircon sand particles was studied by Das et al [8] and they have come to a conclusion that zircon reinforced Al MMCs has better abrasive wear than that of the alumina reinforcement. Fabian et al [9] have developed a MMC by reinforcing tungsten carbide (WC) particles with different weight proportions and have concluded that there is a significant increase in the mechanical properties of the MMC. The mechanical properties such as hardness and tensile strength are significantly increased by the addition of WC reinforcement in the matrix material and they have concluded that the wear resistance of the composite material increases with the increase in WC contents [10 & 11]. Jeykrishnan et al [12] has manufactured aluminum base SiC MMC using stir casting method and have concluded that the mechanical characteristics such as tensile strength and impact properties improves on the addition on SiC particles. Karthik et al [13] have fabricated aluminum MMC by reinforcing TiB2 particles by varying its proportion using stir casting technique and have reported that the tensile strength, impact and hardness values have shown improvement while adding the reinforcement particles. Ravikumar et al [14] have manufactured Al MMC by adding tungsten carbide (WC) particles by varying percentages such as 2%, 4%, 6%, 8% and 10% by weight and investigated the mechanical properties of the composites and have reported that the impact strength and elongation has decreases on adding WC reinforcements. Vijaya Ramnath et al [15] have reported that the MMC fabricated using alumina and boron carbide particles have better mechanical properties such as hardness, impact strength than the un-reinforced aluminum alloy. Baradeswaran et al [16] have fabricated Al7075 MMC by reinforcing B4C particles and have reported that on adding the reinforcements the wear resistance of the material increases and co-efficient of friction of the material decreases. Vijaya Ramnath et al [17, 18] have prepared Al MMC by adding carbon nano-tube (CNT) particles and have concluded that no considerable improvement in hardness properties on adding the CNT particles but a considerable increase in the compressive strength of the material. It has been found that the composites are mostly prepared by the stir casting method and no or little work has been done on reinforcing WC as well as zircon sand with varying proportions to manufacture MMC, which has wide applications in aerospace and automobile industries. 2. Materials and manufacturing 2.1 Materials Aluminum (Al6061) alloy with a density of 2.65g/cm3 has been employed as a matrix material in MMC, as it is well known that Al has good mechanical and thermal properties and finds good applications in marine and aerospace industries. The composition of Al6061 has been given in table 1. In this work for preparing metal–matrix composite, zircon sand and tungsten carbide (WC) in powder form have been used as the reinforcements. WC has a density of 15.63 g/cm³ and a melting point of 2,870 °C. WC is one of the most promising ceramic materials due to its attractive properties, including high strength, density double of that of steel, high melting point of 2870 °C. It has a hexagonal crystal structure and a specific heat capacity of 39.8 J/ (mol·K).
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Table 1. Composition of Al6061 Si
Mg
Fe
Cu
Zn
Cr
Al
0.6
1.0
0.7
0.25
0.25
0.3
Bal
2.2. Manufacturing procedure and results Al silicon alloy bar is cut into small pieces of 10 cm x 3cm x 5cm in dimensions, so that it can be easily placed in the crucible for melting. Al 11.6% silicon alloy has a nominal composition of 10.5% to 13.5% Silicon, 0.05% of lead, tin, chromium, magnesium, nickel each, 0.1% each of titanium and zinc, 0.35% of manganese, 0.4% of iron and 0.03% of copper. The alloy has been theoretically said to have slightly more tensile, compressive and impact strength when compared to pure Al. Zircon sand is a chemical compound which is used in steel foundry, refractory, ceramics and weld fluxes. It is uniform in size and has excellent heat transfer coefficient. Due to its hardness, durability and chemical inertness, zircon persists in sedimentary deposits and is a common constituent of most sands. Stir casting is a primary process of composite production in which continuous stirring of molten metal is done followed by introduction of reinforcements. The resulting mixture is then poured into the die and allowed to solidify. In stir-casting, the particles often tend to form agglomerates, which can be only dissolved by vigorous stirring at high temperature. The advantages of stir castings are simplicity, flexibility, applicability to large quantity, near net shaping, lower cost of processing and easier control of matrix structure. In this work, stir-casting is used for preparing Al metal–matrix composite. This whirlpool technique provides high strength and homogeneous set of Al composite materials. Table 2. Composition of Composites Sample no 1.1
Composite 1 Al 11.6% Si alloy + tungsten carbide 0.5%
1.2
Al 11.6% Si alloy + tungsten carbide 1%
1.3
Al 11.6% Si alloy + tungsten carbide 1.5%
1.4
Al 11.6% Si alloy + tungsten carbide 2%
Sample no 2.1
Composite 2 Al 11.6% Si alloy + zircon sand 0.5%
2.2
Al 11.6% Si alloy + zircon sand 1%
2.3
Al 11.6% Si alloy + zircon sand 1.5%
2.4
Al 11.6% Si alloy + zircon sand 2%
Sample no
Composite 3
3.1
Al 11.6% Si alloy + tungsten carbide 0.5% + zircon sand 0.5%
3.2
Al 11.6% Si alloy + tungsten carbide 1% + zircon sand 1%
3.3
Al 11.6% Si alloy + tungsten carbide 1.5% + zircon sand 1.5%
3.4
Al 11.6% Si alloy + tungsten carbide 2% + zircon sand 2%
In this work, three types of composites namely composite 1, composite 2 and composite 3 have been fabricated. In each composite, four samples have been prepared. Their details were shown in table 2. The experimental arrangement consists of the main furnace and components along with four mild steel stirrer blades. The primary process in the experiment is preheating. Here, the empty crucible and the reinforcement powders, namely WC and zircon sand powders have been heated separately to a temperature close to that of the main process temperature. The melting of the Al alloy has been carried out in the graphite crucible inside the furnace. Initially, the ingot was preheated for 1 hour at 550 °C. Then, the crucible with Al alloy is heated to 840 °C while the preheated powders are mechanically mixed with each other below their melting points. This metal matrix is then kept into the furnace at the
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same temperature. The furnace completely melts the pieces of Al alloy and the preheated zircon sand and WC. Now, stirring mechanism is lowered into the crucible inside the furnace and set at the required depth. The vigorous automatic stirring of the material takes place for 10 min with 600 rpm stir ingrate, thereby uniformly dispersing the additive powders in the Al alloy matrix. The temperature rate of the furnace should be controlled at 840 ±10 °C in the mixing process. The degasser removes all the trapped gases in the crucible and ensures that the temperature of the mixture does not get transferred easily to the atmosphere. This experiment is repeatedly done by varying the compositions of the composite powder for producing different types of composites. Mechanical testing is needed to evaluate the radical properties of materials as well as in developing new composite materials and to control the quality of materials used in design. The ability of a material to withstand a static load can be determined by testing the material in tension or in compression in an universal testing machine (UTM) where the specimen has been prepared as per B-557M standard. The use of compression test is to determine the compression property of composite. The specimen is prepared as per ASTM E8 standard. Impact testing involves the sudden and dynamic application of the load on the composite specimen. This test measures the amount of energy absorbed by the specimen during rupture in joules. The specimen is prepared as per IS 1757 standard. The hardness test measures the resistance offered by a material against the force applied. Brinell hardness test was carried out in this work to determine the deformation of the composite under constant compressive load. The results obtained for tensile test have been furnished in table 3. Also, the results of tensile test are represented in fig 1, 2 and 3 for composite 1, 2 and 3 respectively. From the fig 3, it has been observed that the sample 1.3 shows better tensile strength at 172.02 MPa which is due to the presence of 1.5 % of WC particles. Also, it has been observed that the tensile strength of sample 1.4 is reduced to 82.08 MPa which is the result of increase in the content of WC beyond certain percentage. Hence, it has been concluded that addition of WC particles above 1.5 % reduces the tensile property of the composite. The samples of tensile and compressive strength tests have been prepared as per ASTM E8 standards. Table 3. Result of Tensile Test Name of Composite
1
2
3
Sample no
Tensile strength (MPa)
Yield stress (MPa)
Elongation %
1.1
102.8
91.05
3.54
1.2
146.5
131.11
2.44
1.3
172.2
150.59
3.26
1.4
82.8
73.36
1.96
2.1
105.8
96.06
1.94
2.2
133.9
118.48
2.36
2.3
97.6
89.14
2.34
2.4
97.2
89.14
2.34
3.1
177.4
155.90
2.52
3.2
134.2
120.49
2.36
3.3
140.5
97.03
1.74
3.4
111.7
116.37
1.44
From fig 2 it has been noted that sample 2.2 shows better mechanical behaviour at 133.9 MPa which is due to the presence of 1% zircon sand with aluminium alloy. Since Zr content increases to 1.5%, the mechanical strength (tensile strength) starts decreasing which is due to the result of increase in brittleness of the composite. From fig 3, it is observed that sample 3.1 has mechanical strength of 177.4 MPa which is higher than all the composites fabricated in this work. This is due to the presence of equal amount of WC and Zr of 0.5% each. It is noted that the increase of reinforcement reduces the tensile strength of composites. This is due to increase in hardness of composite by addition of reinforcement and has good agreement with [14]. Hence, it is concluded that 0.5% addition of WC and 0.5% of Zr is a better combination for having good mechanical strength. The compressive strength properties have been furnished in table 4. It has been observed that the sample 3.3 shows the highest compressive load value of 117.55 kN.
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The energy absorbed by all the 12 samples is furnished in table 5. It is found that the impact load or energy absorbed by all the 12 samples is 2 joules. No variation is found in the impact load. Brinell hardness test is used for testing the sample material and it is carried out on all the samples of various compositions of materials. The results are furnished in the table 6. Ball indenter made of hardened steel is used for the test. The diameter of the ball indenter is 10 mm and the applied load is 500 kg/mm2. The samples have been prepared as per the ASTM E10-00 standards. Table 6 shows the hardness values of all the composites.
Fig. 1. Tensile behavior of composite 1
Fig. 2. Tensile behavior of composite 2
Fig. 3. Tensile behavior of composite 3 Table 4. Result of compression test
Name of Composite
1
2
3
Sample no
Compressive load (kN)
1.1 1.2 1.3 1.4 2.1 2.2 2.3 2.4 3.1 3.2 3.3 3.4
88.33 100.91 113.74 87.02 82.90 96.57 106.98 92.04 96.12 108.92 117.55 94.94
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2
3
Sample No 1.1 1.2 1.3 1.4 2.1 2.2 2.3 2.4 3.1 3.2 3.3 3.4
Impact Load (Joules) 2.5 2.3 2.1 1.8 3.4 3.3 3.1 2.8 4.3 4.2 3.9 3.7
The energy absorbed by all the 12 samples is furnished in table 5. It is found that the impact load or energy absorbed by samples decreases as the inclusion of reinforcement particles decreases the hardness of the samples and they are in line with [14]. Brinell hardness test is used for testing the sample material and it is carried out on all the samples of various compositions of materials. The results are furnished in the table 6. Ball indenter made of hardened steel is used for the test. The diameter of the ball indenter is 10 mm and the applied load is 500 kg/mm2. Table 6 shows the hardness values of all the composites. The samples of impact tests have been prepared as per IS 1757 standards.
Table 6. Result of Hardness Test Name of Composite
1
2
3
Sample no
Diameter of indentation (mm)
Hardness (BHN)
1.1
2.9
74.1
1.2
2.9
68.1
1.3
3.1
64.6
1.4
3.3
56.8
2.1
3.1
76.6
2.2
3.1
69.6
2.3
3.1
63.6
2.4
3.2
60.5
3.1
2.8
79.6
3.2
3
69.1
3.3
3
60.1
3.4
3.4
53.4
The hardness of the 4 different samples has been observed. The hardness decreases with the increase in the amount of tungsten carbide, zircon sand or both. The main inference made is that the hardness decreases with the presence of these powders in the metal matrix. Fig. 5 shows the SEM image of the fractured surface of tensile test of sample 1 at 100x magnification and the microscope used in the experiment is SUPRA 520. The general arrangement of aluminum molecules and reinforcements of the aluminum alloy are faintly visible in the image. The aluminum particles which are elliptically shaped in the matrix are more clearly visible at a magnification of 500x as shown in
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fig.6. It is seen that the reinforcements of the matrix and aluminum molecules are distributed unevenly in the region, suggesting that the even distribution of the matrix and reinforcement is done by increasing in the time of stirring during the manufacturing of the sample. The specimen shows a ductile fracture appearance with shearing effects on the surface.
Fig. 4. Hardness graph for all 3 composites
Completely Al particles
Fig. 5. SEM image of sample 1
WC particles
Fig. 6. SEM image of sample 1
Fig. 7 reveals the fractured surface of the sample 2 after tensile test at 108x magnification. The general arrangement of the composite is clearly visible in the image. Many defects, such as micro cracks, porous sites have been avoided by the better stirring time during manufacturing. However, some typical examples of crack paths on the specimen surface of the composites were seen in the image. However, only a few debonding particles are observed compared to sample 1. Fig. 8 shows the microstructure of sample 3 which consist of Al alloy. The picture shows the inner surface of sample 3 which consist of aluminum and other components like Si, WC, Zr etc. It
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consists of tighter packing than the other composites which explains the better tensile and flexural properties of sample 3 compared to sample 2.
Crack Initiation
Zircon sand particles
Fig. 7. SEM image of sample 2
Fig. 8. SEM image of sample 3
3. Conclusions The hardness of the 4 different samples has been observed. The hardness decreases with the increase in the amount of tungsten carbide, zircon sand or both. The main inference made is that the hardness decreases with the presence of these powders in the metal matrix. In this work, twelve different samples are fabricated and the following inferences are made; (1) It has been inferred that the tensile strength of sample 3.1 has marginally higher than that of other samples because of its more Al particle content with all the other materials of minimum composition used (WC 0.5% and Zr 0.5%) and sample three has the second highest value of tensile strength when compared to other samples (tungsten carbide 1.5%). (2) It has been found that sample 3.3 (tungsten carbide 1.5% and zircon sand 1.5%) has more compressive strength than all the other samples (117.55 kN). (3) It is found that the impact strength decreases on addition of reinforcements. (4) Also, Brinell hardness test for all the 12 samples are noted and the maximum hardness is found to be 79.6 (BHN) for Al 11.6% Si alloy + tungsten carbide 0.5% + zircon sand 0.5% composite. (5) The SEM analysis has been completed on the composite materials and has been showcased. References [1]. Daniel B. Miracle and Steven L. Donaldson, “Introduction to composites”, ASM Handbook of composite materials, Vol. 21. [2]. Tamer Ozben, ErolKilickap, Orhan Çakir, “Investigation of mechanical and machinability properties of SiC particle reinforced Al-MMC”, Journal of materials processing technology, Vol. 198, (2008) 220-225. [3]. B Bobic, S. Mitrovic, M. Babic, I. Bobic, “Corrosion of Metal-Matrix Composites with Aluminium Alloy Substrate”, Tribology in industry, Volume 32, No. 1, 2010. [4]. M. Ramachandra and K. Radhakrishna, “Effect of reinforcement of flyash on sliding wear, slurry erosive wear and corrosive behavior of aluminium matrix composite”, Wear Vol. 262, 2007, 1450-1462. [5] Seo YH, Kang CG, “Effects of hot extrusion through a curved die on the mechanical properties of SiC/Al composites fabricated by melt stirring”, Compos Sci Tech 1999:643-54. [6]. Hosseini N, Karimzadeh F, Abbasi MH, Enayati MH, “Tribological properties of Al6061-Al2O3 nano-composite prepared by milling and hot pressing”, Materials design, Vol. 31, 2010, pp. 4777- 4785.
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[7]. J. Jenix Rino, Dr. D. Sivalingappa, Halesh Koti and V. Daniel Jebin, “Properties of Al6063 MMC reinforced with zicon sand and alumina”, IOSR journal of Mechanical and Civil Engineering, Vol. 5, Issue: 5, 2013, pp. 72-77. [8]. Sanjeev Das, Siddhartha Das and Karabi Das, “Abrasive wear of zircon sand and alumina reinforced Al–4.5 wt% Cu alloy matrix composites – A comparative study”, Composites Science and Technology, Vol. 67, 2007, pp.746. [9]. S. Jerry Andrews Fabian, B. Selvam, “Densification behaviour of Aluminium reinforced with Tungsten Carbide particulate Metal Matrix Composite processed by P/M”, IOSR Journal of Mechanical and Civil Engineering, pp. 24-29. [10]. Amarnath.G, K.V. Sharma, “Microstructure and tribological properties of nano-particulate WC/Al metal matrix composites”, International journal of mechanical engineering and technology, Vol. 4, Issue 2, 2013, pp. 178-188. [11] Hari Prasada Rao Pydi, Balamurugan Adhithan, A.Syed Bava Bakrudeen ,“Microstructure Exploration of the Aluminum-Tungsten Carbide Composite with different Manufacturing circumstances”, International Journal of Soft Computing and Engineering, ISSN: 2231-2307, Vol. 2, Issue: 6, 2013. [12]. J. Jeykrishnan, B. Vijaya Ramnath, X. Hervin Savariraj, R. David Prakash, V. R. Dhinesh Rajan and D. Dinesh Kumar, “Investigation on tensile and impact behavior of aluminum base silicon carbide metal matrix composites”, Indian journal of science and technology, Vol. 9 (37), 2016. [13]. J. Jeykrishnan, S. Jayanthi Nathan and M.R. Karthik, “Fabrication and Characterization of Aluminum Titanium Di-Boride Metal Matrix Composites Using Stir Casting Technique”, International Journal of Mechanical Engineering and Technology, Vol. 8 (4), 2017, pp. 13–18. [14]. K. Ravikumar, K. Kiran, V.S. Sreebalaji, “Characterization of mechanical properties of aluminium/tungsten carbide composites”, Measurement, Vol. 102, 2017, pp. 142-149. [15]. B. Vijaya Ramnath, C. Elanchezhian, M. Jaivignesh, S. Rajesh, C. Parswajinan, A. Siddique Ahmed Ghias, Evaluation of mechanical properties of aluminium alloy– alumina–boron carbide metal matrix composites, Materials and Design, Vol. 58, 2014, pp. 332–338. [16]. Baradeswaran A, Perumal AE, “Influence of B4C particles on the tribological and mechanical properties of Al 7075 – B4C composites”, Composites: Part B, Vol. 54 (1), 2013, pp. 146-152. [17]. B. Vijaya Ramnath, C. Parswajinan, C. Elanchezhian, S. Venkatesan Pragadeesh, C. Kavin, P.R. Ram kishore, V. Sabarish, “Experimental Investigation on Compression and Chemical Properties of Aluminium Nano Composite”, Applied Mechanics and Materials, Vol. 680, 2014, pp. 7-10. [18]. C. Parswajinan, B. Vijaya Ramnath, M. Vetrivel, C. Elanchezhian, K. Loganathan, R. Sarvesh, C. Rohit Prasanna, R.N. Karthick Babu, “Experimental investigation of Mechanical and chemical properties of aluminum reinforced with MWCNT”, Applied Mechanics and Materials, Vol. 766-767, 2015, pp. 28-292.