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Study on mechanical properties of graphite particulates reinforced aluminium matrix composite fabricated by stir casting technique
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 2945–2950
www.materialstoday.com/proceedings
ICAMA 2016
Study on mechanical properties of graphite particulates reinforced aluminium matrix composite fabricated by stir casting technique V. Mohanavela*, K. Rajanb, S. Suresh Kumarc, G. Vijayand, M. S. Vijayanande b
a Department of Mechanical Engineering, St. Peter’s University, Chennai, India. Department of Mechanical Engineering, Dr.MGR Educational & Research Institute University, Chennai, India. c Department of Mechanical Engineering, Panimalar Polytechnic College, Chennai, India. d Department of Mechanical Engineering, Ganadipathy Tulsi’s Jain Engineering College, Vellore, India. e Department of Mechanical Engineering, Paavai Engineering College, Namakkal, India.
Abstract The lineage of applied materials science is always in demand for light weight and highly performing materials. Such materials would find their applications in aircraft, structural, non-structural and automobile industries, etc. The present research study focuses on the production of aluminium (AA6351) matrix composites reinforced in different mass fractions of graphite particulates by using stir casting method. The mass fraction of reinforcement was varied from 0% to 12% in stages of 4%. Hardness and tensile strength of the composite were investigated. The microstructures of the produced composites were examined by scanning electron micrographic test. The SEM images revealed the non-homogeneous distribution of graphite (Gr) particles in the matrix and this may be due to low density of graphite. The test results revealed that the mechanical properties of the composite decrease with increase in the mass fraction of graphite particle content, this may be due to poor interfacial bonding between the reinforcement and the matrix. The brittle nature of the reinforcing particles (graphite) plays a vital role in decreasing the mechanical properties because the graphite as a soft reinforcement is brittle in nature and so it enhanced the brittleness in the AMCs. © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Advanced Materials and Applications (ICAMA 2016). Keywords:AA6351 alloy, Graphite, Hardness, Scanning Electron Microscope (SEM), UTS.
1. Introduction Titanium, aluminium, nickel and magnesium alloys are the popular matrix metals presently in vogue, which are particularly suitable for automotive, defence and aerospace applications [1]. *Corresponding author. Tel : +91 9043392344 E-mail address : [email protected] 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Advanced Materials and Applications (ICAMA 2016).
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In the last two decades, particulate reinforced aluminium matrix composites (PRAMCs) have the potential to replace the conventional materials in several fields of applications like transportation, military, marine as well as in various advanced engineering industries [2]. Aluminium matrix composites (AMCs) are being considered as a group of advanced materials for their lightweight, low thermal expansion coefficient, outstanding wear resistance properties and good mechanical properties [3]. The structure and the properties of these composites are majorly showing influence on the type, shape, size and weight fraction of the reinforcement. Size and wt% of the reinforcement works as an vital role in manipulating the tribological and mechanical properties of the composites [4]. Tribological and mechanical behaviors of AMCs can be notably enriched by adding reinforcing particles in the aluminum matrix alloy. Extensively used fabrication techniques for aluminum matrix composites involve compocasting, vacuum casting, powder metallurgy, stir casting, insitu casting and squeeze casting [5]. Among those avaliable process, stir casting process is the most promising one for producing particulate reinforced aluminum matrix composites. This technique obtains homogeneous dissemination of reinforcement particles in the matrix alloy [6]. The AMCs can be reinforced with several types of reinforcement particles like B4C [7], SiC [8], ZrB2 [9], Al2O3 [10], Gr [11] and TiB2 [12], while lots of investigators have employed Al2O3, B4C and SiC as reinforcing materials. A very few investigation works have been conducted on graphite (Gr) as the reinforcement. Some latest outcomes have endeavored to produce the graphite particulates reinforced aluminium matrix composites and then were reported in the literature [13-16]. A. Baradeswaran et al., [13] analyzed the effect of Gr particles on microstructure and tribological properties of AA7075/Gr AMCs. They concluded that the presence of Gr particle offers improved wear resistance to the composites. Pradeep sharma et al., [14] examined the influence of Gr particle content and they stated the mechanical behavior of Gr particle reinforced AA6082 composites manufactured by stir casting method. A. Baradeswaran et al., [15] have reported on the influence of Gr particle on the flexural strength and hardness of AA7075-Gr composites fabricated by stir casting process and found that mechanical properties of the composites decreased with increased graphite particle content. The work of Akhlaghi et al., [16] stated about the reduction in mechanical properties of AA2024/Gr AMCs and concluded that on increasing graphite content the strengthening effect of alloy matrix decrease. To the best of our knowledge, a very limited findings have been reported on the mechanical behaviour of composites reinforced with graphite particle. Moreover, no research work have been done on Gr reinforced AA6351 composites which have used stir csating process for fabrication. So, this research study is still vacant and more number of works can be done on this specific field. In the current investigation, an attempt has been made to manufacture AA6351/Gr AMC with various mass fractions ranging from 0 to 12%. The increase in Gr contents tends to decrease the hardness and the tensile strength of the composites. 2. Experimental Procedure In the present investigation, AA6351-Gr composites were manufactured by stir casting technique. These produced composites were characterized for several mechanical properties and compared with the plain AA6351 matrix alloy. The process details are as follows: 2.1 Materials The matrix material for the research study selected is aluminum alloy 6351. The chemical composition of AA6351 is Si 1.0, Fe 0.60, Cu 0.10, Mn 0.5, Mg 0.7, Cr 0.25, Zn 0.10, Ti 0.20, and the balance is aluminum (wt.%). The reinforcing particle was Gr (50µm) supplied by Krishmet India Pvt., Chennai. 2.2 Fabrication process A liquid state stir casting method has been adopted to prepare the AA6351/Gr AMCs. The AA6351 aluminum alloy was melted in an induction electric resistance furnace to a temperature of about 850oC. The gauged weight percentage of Gr particles were preheated to 500oC. They are then incorporated to the matrix aluminum melt. The matrix-reinforcement melt was stirred continuously at 400rpm and it was being continued for 30minutes. Then the well mixed melt was poured into the preheated die kept ready for the purpose. The weight fraction of reinforcement (Gr) was varied from 0% to 12% in a stage of 4%. The important process parameters are depicted in Table 1. The manufactured typical AA6351/Gr AMCs are exhibited in fig. 1.
V. Mohanavel et.al/ Materials Today: Proceedings 5 (2018) 2945–2950
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Table 1. Important process parameters of stir casting. Parameters Preheated temperature of graphite particles Temperature of melt charge
Value 500 850
Units (oC) (oC)
Particles feed rate Stirrer speed Stirring time
0.9-1.4 400 30
(g/s) (rpm) 30
2.3 Testing of composites The prepared samples were machined and cut so as to prepare the specimens for different studies. Hardness of the unreinforced matrix alloy and the produced composites were estimated by conducting Rockwell hardness testing at 15 kgf load which is applied constantly for a dwell time of five seconds at six different locations and the average values are then obtained and they are reported consequently. Tensile tests were carried out on the computerised 100KN Servo hydraulic universal testing machine (Model- INSTRON 8801) with a strain rate of 1.0 mm/min at room temperature. Tensile tests were performed as per ASTM E8 standard at room temperature (30°C). For every combination, three tests were conducted and the average values are reported. The samples are polished using a normal metallographic procedure. Keller’s reagent is used as etchant and the microstruture of the specimens were observed consequently by Scanning electron microscopy. The microstructural images were recorded using CarlZeiss field emission scanning electron microscope (FESEM).
Fig. 1. The manufactured stir cast AA6351-Gr AMCs.
Fig. 2. SEM image of as cast AA6351 alloy
3. Results and Discussion 3.1 Examination of microstructure Fig. 2 shows the scanning electron micrograph (SEM) image of as cast AA6351 matrix alloy. Microstructure of plain matrix AA6351 alloy shows the occurrence of Magnesium (Mg) and Silica (Si) particles which are the main elements of base AA6351 alloy. Fig. 3(a-d) shows the SEM photographs of produced composites. The SEM photographs revealed the non-homogeneous distribution of graphite (Gr) particles in the matrix and this may be owing to the low density and higher weight fraction of graphite particle content in the matrix [14]. Besides, the nonhomogeneous particle distribution often results in poor mechanical properties of the composite.
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V. Mohanavel et.al / Materials Today: Proceedings 5 (2018) 2945–2950
Fig. 3. SEM image of AA6351-Graphite AMCs: (a) 4 wt.% Gr, (b) 8 wt.% Gr and (c-d) 12 wt.% Gr.
3.2 Hardness The effect of Gr content on hardness of AA6351/Gr AMCs is displayed in fig 4. The hardness has been noticed to decrease with the increase in Gr particles and it is significantly lower than the hardness of the base AA6351 matrix alloy. This decrease in hardness may be owing to occurrence of non-homogeneous dissemination of graphite particulates in the matrix.
Fig. 4. Variation of hardness with weight percentage of Gr addition.
V. Mohanavel et.al/ Materials Today: Proceedings 5 (2018) 2945–2950
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The brittle and soft graphite particles cause them float in the melt and resulted into poor interfacial bonding between reinforcement (Gr) and matrix alloy (AA6351). This poor interfacial bonding of graphite particles reduce the hardness of the composites [13, 15]. 3.3 Tensile strength The effect of Gr content on tensile strength of AA6351/Gr AMCs is displayed in fig 5. The test results show that the tensile strength of the composite decreases with increase in the mass fraction of graphite particle content, this may be due to poor interfacial bonding between the reinforcement and the matrix. The brittle nature of the reinforcing particles (graphite) plays a vital role in decreasing the mechanical properties because the graphite as a soft reinforcement is brittle in nature and it enhanced the brittleness in the AMCs [13]. Moreover, the less cluster of Gr particles reduces the load bearing capacity of the AMCs, therefore tensile strength of the composite is decreased.
Fig. 5. Variation of UTS with weight percentage of Gr addition.
Conclusion The following salient conclusions were obtained from this present research. The AA6351-Gr composites were manufactured by the liquid state stir casting technique. The hardness and the tensile strength of the composites decreased with the increase in wt.% of Gr particulates. The inclusion of Gr particulates to the AA6351 matrix has led to reduce the mechanical properties of the composites and this may be due to low density and brittle in nature of graphite particle content. The SEM photographs exhibited the non-homogeneous distribution of the Gr particles in the matrix alloy. Acknowledgement The authors are grateful to the School of Mechanical Engineering, VIT University, Vellore and Metmech Engineers Lab, Chennai for extending the facilities to carry out this investigation. The authors are also thankful to Mr. Xavier Arockia Raj, Mr. Jayaraj, Mr. K. Subramani, Mr. Vijayakumar and Mr. Premkumar for their effective assistance offered to execute the above work. References [1] Thambu Sornakumar, Marimuthu Kathiresan, Machning studies of die cast aluminum alloy-silicon carbide composites, International Journal of Minerals, Metallurgy and Materials, Vol 17 Issue 5 (2010) 648-653. [2] Yu Ma, Zhe Chen, Mingliang Wang, Dong Chen, Naiheng Ma, Haowei Wang, High Cycle fatigue behavior of the in-situ TiB2/7050 composite, Materials Science and Engineering A, 640 (2015) 350-356. [3] V. Mohanavel, K. Rajan, K.R. Senthil kumar, Study on Mechanical properties of AA6351 alloy reinforced with titanium di-boride (TiB2) composite by in situ casting method, Applied Mechanics and Materials, 787 (2015) 583-587. [4] H.B. Michael Rajan, I. Dinaharan, S. Rambalan, E.T. Akinlabi, Influence of friction stir processing on microstructure and properties of AA7075/TiB2 in situ composite, Journal of Alloys and Compounds, 657 (2016) 250-260.
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[5] V. Mohanavel, K. Rajan, S. Arul, P.V. Senthil, Mechanical behaviour of hybrid composite (AA6351+Al2O3+Gr) fabricated by stir casting method, 5th International Conference on Materials Processing and characterization (ICMPC), 12-13 March, GRIET, Hyderabad, India, 2016, Materials Today Proceedings, Elsevier (in press). [6] V. Mohanavel, K. Rajan, M. Ravichandran, Synthesis, characterization and properties of stir cast AA6351-aluminium nitride (AlN) composites, Journal of Materials Research, Vol 31 Issue 2 (2016) 3824-3831. [7] A. Baradeswaran, A. Elaya Perumal, J.P. Davim, Effect of B4C on mechanical properties and tribological behaviour of AA6061-B4C composites, Journal of the Balkan Tribological Association, Vol 19 Issue 2 (2013) 230-239. [8] G.H. Majzoobi, A. Atrian, M.H. Enayati, Tribological properties of Al7075-SiC nanocomposites prepared by hot dynamic compaction, Composite Interface, Vol 22 Issue 7 (2015) 579-593. [10] Y. Sahin, K. Emre Oksuz, Tribological behaviour of Al2014-Al2O3 particle reinforced composites produced by powder metallurgy method, Journal of the Balkan Tribological Association, Vol 19 Issue 2 (2013) 190-201. [11] A. Baradeswaran, A. Elayaperumal, A review on the state of art of wear characteristics of aluminium alloy metal matrix composites, Journal of the Balkan Tribological Association, Vol 19 Issue 2 (2013) 165-177. [12] S. Suresh, N. Shenbaga Vinayaga Moorthi, N. Selvakumar, S.C. Vettivel, Tribological, tensile and hardness behavior of TiB2 reinforced aluminium metal matrix composite, Journal of the Balkan Tribological Association, Vol 20 Issue 3 (2014) 380-394. [13] A. Baradeswaran, A. Elayaperumal, Effect of graphite on tribological and mechanical properties of AA7075 composites, Tribology Transactions, 58 (2016) 1-6. [14] Pardeep Sharma, Satpal Sharma, Dinesh Khanduja, A study on microstructure of aluminium matrix composites, Journal of Asian Ceramics Societies, 3 (2015) 240-244. [15] A. Baradeswaran, A. Elayaperumal, Wear and mechanical charcteristics of Al7075/graphite composites, Composites: Part B, 56 (2014) 472476. [16] F. Akhalagi, Z.A. Bidaki, Influence of graphite content on dry sliding and oil impregnated sliding wear behaviour of Al2024-Gr composite produced by in situ powder metallurgy method, Wear, 266 (2009) 37-45.
ScienceDirect Materials Today: Proceedings 5 (2018) 2945–2950
www.materialstoday.com/proceedings
ICAMA 2016
Study on mechanical properties of graphite particulates reinforced aluminium matrix composite fabricated by stir casting technique V. Mohanavela*, K. Rajanb, S. Suresh Kumarc, G. Vijayand, M. S. Vijayanande b
a Department of Mechanical Engineering, St. Peter’s University, Chennai, India. Department of Mechanical Engineering, Dr.MGR Educational & Research Institute University, Chennai, India. c Department of Mechanical Engineering, Panimalar Polytechnic College, Chennai, India. d Department of Mechanical Engineering, Ganadipathy Tulsi’s Jain Engineering College, Vellore, India. e Department of Mechanical Engineering, Paavai Engineering College, Namakkal, India.
Abstract The lineage of applied materials science is always in demand for light weight and highly performing materials. Such materials would find their applications in aircraft, structural, non-structural and automobile industries, etc. The present research study focuses on the production of aluminium (AA6351) matrix composites reinforced in different mass fractions of graphite particulates by using stir casting method. The mass fraction of reinforcement was varied from 0% to 12% in stages of 4%. Hardness and tensile strength of the composite were investigated. The microstructures of the produced composites were examined by scanning electron micrographic test. The SEM images revealed the non-homogeneous distribution of graphite (Gr) particles in the matrix and this may be due to low density of graphite. The test results revealed that the mechanical properties of the composite decrease with increase in the mass fraction of graphite particle content, this may be due to poor interfacial bonding between the reinforcement and the matrix. The brittle nature of the reinforcing particles (graphite) plays a vital role in decreasing the mechanical properties because the graphite as a soft reinforcement is brittle in nature and so it enhanced the brittleness in the AMCs. © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Advanced Materials and Applications (ICAMA 2016). Keywords:AA6351 alloy, Graphite, Hardness, Scanning Electron Microscope (SEM), UTS.
1. Introduction Titanium, aluminium, nickel and magnesium alloys are the popular matrix metals presently in vogue, which are particularly suitable for automotive, defence and aerospace applications [1]. *Corresponding author. Tel : +91 9043392344 E-mail address : [email protected] 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Advanced Materials and Applications (ICAMA 2016).
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V. Mohanavel et.al / Materials Today: Proceedings 5 (2018) 2945–2950
In the last two decades, particulate reinforced aluminium matrix composites (PRAMCs) have the potential to replace the conventional materials in several fields of applications like transportation, military, marine as well as in various advanced engineering industries [2]. Aluminium matrix composites (AMCs) are being considered as a group of advanced materials for their lightweight, low thermal expansion coefficient, outstanding wear resistance properties and good mechanical properties [3]. The structure and the properties of these composites are majorly showing influence on the type, shape, size and weight fraction of the reinforcement. Size and wt% of the reinforcement works as an vital role in manipulating the tribological and mechanical properties of the composites [4]. Tribological and mechanical behaviors of AMCs can be notably enriched by adding reinforcing particles in the aluminum matrix alloy. Extensively used fabrication techniques for aluminum matrix composites involve compocasting, vacuum casting, powder metallurgy, stir casting, insitu casting and squeeze casting [5]. Among those avaliable process, stir casting process is the most promising one for producing particulate reinforced aluminum matrix composites. This technique obtains homogeneous dissemination of reinforcement particles in the matrix alloy [6]. The AMCs can be reinforced with several types of reinforcement particles like B4C [7], SiC [8], ZrB2 [9], Al2O3 [10], Gr [11] and TiB2 [12], while lots of investigators have employed Al2O3, B4C and SiC as reinforcing materials. A very few investigation works have been conducted on graphite (Gr) as the reinforcement. Some latest outcomes have endeavored to produce the graphite particulates reinforced aluminium matrix composites and then were reported in the literature [13-16]. A. Baradeswaran et al., [13] analyzed the effect of Gr particles on microstructure and tribological properties of AA7075/Gr AMCs. They concluded that the presence of Gr particle offers improved wear resistance to the composites. Pradeep sharma et al., [14] examined the influence of Gr particle content and they stated the mechanical behavior of Gr particle reinforced AA6082 composites manufactured by stir casting method. A. Baradeswaran et al., [15] have reported on the influence of Gr particle on the flexural strength and hardness of AA7075-Gr composites fabricated by stir casting process and found that mechanical properties of the composites decreased with increased graphite particle content. The work of Akhlaghi et al., [16] stated about the reduction in mechanical properties of AA2024/Gr AMCs and concluded that on increasing graphite content the strengthening effect of alloy matrix decrease. To the best of our knowledge, a very limited findings have been reported on the mechanical behaviour of composites reinforced with graphite particle. Moreover, no research work have been done on Gr reinforced AA6351 composites which have used stir csating process for fabrication. So, this research study is still vacant and more number of works can be done on this specific field. In the current investigation, an attempt has been made to manufacture AA6351/Gr AMC with various mass fractions ranging from 0 to 12%. The increase in Gr contents tends to decrease the hardness and the tensile strength of the composites. 2. Experimental Procedure In the present investigation, AA6351-Gr composites were manufactured by stir casting technique. These produced composites were characterized for several mechanical properties and compared with the plain AA6351 matrix alloy. The process details are as follows: 2.1 Materials The matrix material for the research study selected is aluminum alloy 6351. The chemical composition of AA6351 is Si 1.0, Fe 0.60, Cu 0.10, Mn 0.5, Mg 0.7, Cr 0.25, Zn 0.10, Ti 0.20, and the balance is aluminum (wt.%). The reinforcing particle was Gr (50µm) supplied by Krishmet India Pvt., Chennai. 2.2 Fabrication process A liquid state stir casting method has been adopted to prepare the AA6351/Gr AMCs. The AA6351 aluminum alloy was melted in an induction electric resistance furnace to a temperature of about 850oC. The gauged weight percentage of Gr particles were preheated to 500oC. They are then incorporated to the matrix aluminum melt. The matrix-reinforcement melt was stirred continuously at 400rpm and it was being continued for 30minutes. Then the well mixed melt was poured into the preheated die kept ready for the purpose. The weight fraction of reinforcement (Gr) was varied from 0% to 12% in a stage of 4%. The important process parameters are depicted in Table 1. The manufactured typical AA6351/Gr AMCs are exhibited in fig. 1.
V. Mohanavel et.al/ Materials Today: Proceedings 5 (2018) 2945–2950
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Table 1. Important process parameters of stir casting. Parameters Preheated temperature of graphite particles Temperature of melt charge
Value 500 850
Units (oC) (oC)
Particles feed rate Stirrer speed Stirring time
0.9-1.4 400 30
(g/s) (rpm) 30
2.3 Testing of composites The prepared samples were machined and cut so as to prepare the specimens for different studies. Hardness of the unreinforced matrix alloy and the produced composites were estimated by conducting Rockwell hardness testing at 15 kgf load which is applied constantly for a dwell time of five seconds at six different locations and the average values are then obtained and they are reported consequently. Tensile tests were carried out on the computerised 100KN Servo hydraulic universal testing machine (Model- INSTRON 8801) with a strain rate of 1.0 mm/min at room temperature. Tensile tests were performed as per ASTM E8 standard at room temperature (30°C). For every combination, three tests were conducted and the average values are reported. The samples are polished using a normal metallographic procedure. Keller’s reagent is used as etchant and the microstruture of the specimens were observed consequently by Scanning electron microscopy. The microstructural images were recorded using CarlZeiss field emission scanning electron microscope (FESEM).
Fig. 1. The manufactured stir cast AA6351-Gr AMCs.
Fig. 2. SEM image of as cast AA6351 alloy
3. Results and Discussion 3.1 Examination of microstructure Fig. 2 shows the scanning electron micrograph (SEM) image of as cast AA6351 matrix alloy. Microstructure of plain matrix AA6351 alloy shows the occurrence of Magnesium (Mg) and Silica (Si) particles which are the main elements of base AA6351 alloy. Fig. 3(a-d) shows the SEM photographs of produced composites. The SEM photographs revealed the non-homogeneous distribution of graphite (Gr) particles in the matrix and this may be owing to the low density and higher weight fraction of graphite particle content in the matrix [14]. Besides, the nonhomogeneous particle distribution often results in poor mechanical properties of the composite.
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Fig. 3. SEM image of AA6351-Graphite AMCs: (a) 4 wt.% Gr, (b) 8 wt.% Gr and (c-d) 12 wt.% Gr.
3.2 Hardness The effect of Gr content on hardness of AA6351/Gr AMCs is displayed in fig 4. The hardness has been noticed to decrease with the increase in Gr particles and it is significantly lower than the hardness of the base AA6351 matrix alloy. This decrease in hardness may be owing to occurrence of non-homogeneous dissemination of graphite particulates in the matrix.
Fig. 4. Variation of hardness with weight percentage of Gr addition.
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The brittle and soft graphite particles cause them float in the melt and resulted into poor interfacial bonding between reinforcement (Gr) and matrix alloy (AA6351). This poor interfacial bonding of graphite particles reduce the hardness of the composites [13, 15]. 3.3 Tensile strength The effect of Gr content on tensile strength of AA6351/Gr AMCs is displayed in fig 5. The test results show that the tensile strength of the composite decreases with increase in the mass fraction of graphite particle content, this may be due to poor interfacial bonding between the reinforcement and the matrix. The brittle nature of the reinforcing particles (graphite) plays a vital role in decreasing the mechanical properties because the graphite as a soft reinforcement is brittle in nature and it enhanced the brittleness in the AMCs [13]. Moreover, the less cluster of Gr particles reduces the load bearing capacity of the AMCs, therefore tensile strength of the composite is decreased.
Fig. 5. Variation of UTS with weight percentage of Gr addition.
Conclusion The following salient conclusions were obtained from this present research. The AA6351-Gr composites were manufactured by the liquid state stir casting technique. The hardness and the tensile strength of the composites decreased with the increase in wt.% of Gr particulates. The inclusion of Gr particulates to the AA6351 matrix has led to reduce the mechanical properties of the composites and this may be due to low density and brittle in nature of graphite particle content. The SEM photographs exhibited the non-homogeneous distribution of the Gr particles in the matrix alloy. Acknowledgement The authors are grateful to the School of Mechanical Engineering, VIT University, Vellore and Metmech Engineers Lab, Chennai for extending the facilities to carry out this investigation. The authors are also thankful to Mr. Xavier Arockia Raj, Mr. Jayaraj, Mr. K. Subramani, Mr. Vijayakumar and Mr. Premkumar for their effective assistance offered to execute the above work. References [1] Thambu Sornakumar, Marimuthu Kathiresan, Machning studies of die cast aluminum alloy-silicon carbide composites, International Journal of Minerals, Metallurgy and Materials, Vol 17 Issue 5 (2010) 648-653. [2] Yu Ma, Zhe Chen, Mingliang Wang, Dong Chen, Naiheng Ma, Haowei Wang, High Cycle fatigue behavior of the in-situ TiB2/7050 composite, Materials Science and Engineering A, 640 (2015) 350-356. [3] V. Mohanavel, K. Rajan, K.R. Senthil kumar, Study on Mechanical properties of AA6351 alloy reinforced with titanium di-boride (TiB2) composite by in situ casting method, Applied Mechanics and Materials, 787 (2015) 583-587. [4] H.B. Michael Rajan, I. Dinaharan, S. Rambalan, E.T. Akinlabi, Influence of friction stir processing on microstructure and properties of AA7075/TiB2 in situ composite, Journal of Alloys and Compounds, 657 (2016) 250-260.
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[5] V. Mohanavel, K. Rajan, S. Arul, P.V. Senthil, Mechanical behaviour of hybrid composite (AA6351+Al2O3+Gr) fabricated by stir casting method, 5th International Conference on Materials Processing and characterization (ICMPC), 12-13 March, GRIET, Hyderabad, India, 2016, Materials Today Proceedings, Elsevier (in press). [6] V. Mohanavel, K. Rajan, M. Ravichandran, Synthesis, characterization and properties of stir cast AA6351-aluminium nitride (AlN) composites, Journal of Materials Research, Vol 31 Issue 2 (2016) 3824-3831. [7] A. Baradeswaran, A. Elaya Perumal, J.P. Davim, Effect of B4C on mechanical properties and tribological behaviour of AA6061-B4C composites, Journal of the Balkan Tribological Association, Vol 19 Issue 2 (2013) 230-239. [8] G.H. Majzoobi, A. Atrian, M.H. Enayati, Tribological properties of Al7075-SiC nanocomposites prepared by hot dynamic compaction, Composite Interface, Vol 22 Issue 7 (2015) 579-593. [10] Y. Sahin, K. Emre Oksuz, Tribological behaviour of Al2014-Al2O3 particle reinforced composites produced by powder metallurgy method, Journal of the Balkan Tribological Association, Vol 19 Issue 2 (2013) 190-201. [11] A. Baradeswaran, A. Elayaperumal, A review on the state of art of wear characteristics of aluminium alloy metal matrix composites, Journal of the Balkan Tribological Association, Vol 19 Issue 2 (2013) 165-177. [12] S. Suresh, N. Shenbaga Vinayaga Moorthi, N. Selvakumar, S.C. Vettivel, Tribological, tensile and hardness behavior of TiB2 reinforced aluminium metal matrix composite, Journal of the Balkan Tribological Association, Vol 20 Issue 3 (2014) 380-394. [13] A. Baradeswaran, A. Elayaperumal, Effect of graphite on tribological and mechanical properties of AA7075 composites, Tribology Transactions, 58 (2016) 1-6. [14] Pardeep Sharma, Satpal Sharma, Dinesh Khanduja, A study on microstructure of aluminium matrix composites, Journal of Asian Ceramics Societies, 3 (2015) 240-244. [15] A. Baradeswaran, A. Elayaperumal, Wear and mechanical charcteristics of Al7075/graphite composites, Composites: Part B, 56 (2014) 472476. [16] F. Akhalagi, Z.A. Bidaki, Influence of graphite content on dry sliding and oil impregnated sliding wear behaviour of Al2024-Gr composite produced by in situ powder metallurgy method, Wear, 266 (2009) 37-45.