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Effect of ZrB2 content on mechanical and microstructural characterization of AA6063 aluminum matrix composites
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 13601–13605
www.materialstoday.com/proceedings
ICMMM - 2017
Effect of ZrB2 content on mechanical and microstructural characterization of AA6063 aluminum matrix composites V. Mohanavela*, S. Suresh Kumarb, T. Sathishc, K.T. Anandb b
a Department of Mechanical Engineering, Kingston Engineering College, Vellore, India. Department of Mechanical Engineering, Panimalar Group of Institutions, Chennai, India. c Department of Mechanical Engineering, St. Peter’s University, Chennai, India.
Abstract The in situ AA6063/ZrB2 composite is being widely manufactured by the direct metal reaction technique. The potassium hexafluorozirconate (K2ZrF6) and the potassium tetrafluoroborate (KBF4) were used to synthesize the ZrB2 particles through the salt reaction method. The weight percentage of ZrB2 varied from 0 to 10 in steps of 5. The exothermic reaction between the inorganic salts, K2ZrF6 and KBF4 and the molten aluminium leads to the formation of ZrB2. Micro hardness and tensile strength of the composite were examined. The prepared composites were characterized by scanning electron microscope (SEM). SEM micrographs display that the particles are nearly homogeneous dissemination in the AA6063 matrix alloy. The increase in weight percentage of zirconium diboride particles improves the mechanical properties of the composite. The test results showed that the AA6063/10wt.% of ZrB2 composites had revealed greater hardness and tensile strength than the base matrix.
© 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
Keywords: AA6063 alloy, Ultimate Tensile Strength, Scanning Electron Microscope, ZrB2.
*Corresponding author. Tel : +91 9043392344 E-mail address : [email protected]
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
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V. Mohanavel/ Materials Today: Proceedings 5 (2018) 13601–13605
1. Introduction Titanium, aluminium and magnesium alloys are the most popular matrix metals presently in vogue, which are particularly suitable for automobile, defence, structural and aircraft applications [1]. In the last three decades, metal matrix composites (MMCs) 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]. Extensively employed fabrication methods for aluminum matrix composites involve stir casting, compocasting, vacuum casting, powder metallurgy, centrifugal casting, insitu casting and squeeze casting [4-5]. Among those available process, insitu method is most economical and is always preferred. Insitu formed particles reveal strong interfacial bonding with the matrix. Insitu method overcomes the limitations of stir casting process such as improper wetting of reinforcement particles and density dependence of particles and its associated problems like sinking and floating of particles [6]. In situ ceramic particles, such as Al2O3, TiB2, AlN, TiC, B4C and ZrB2 have been widely used as reinforcements in aluminum-based composites [7]. Some research findings on aluminum matrix composites (AMCs) reinforced with ZrB2 particles were stated in the literature [8-10]. David Raja Selvam et al., [8] characterized the mechanical behavior of AA7075/ZrB2 composites fabricated by insitu casting method. They stated that the hardness and tensile strength of the composites are enhanced with the increase in weight percentage of ZrB2 reinforcement content. I. Dinaharan et al., [9] found that the hardness, tensile strength and wear resistance of AA6061/ZrB2 composite enriched as the weight fraction of ZrB2 was increased. Narendra Kumar et al., [10] investigated the influence of ZrB2 particles on microstructure and mechanical properties of AA5052/ZrB2 AMC. They reported that the presence of ZrB2 reinforcement particles enhanced the mechanical behaviors to the composite. From the literature, it is evident that very few information is available on AA6063 alloy based ceramic particles reinforced composites. To the best of our knowledge, no work is done on AA6063/ZrB2 composite. In the present research study, the AA6063 aluminum alloy was reinforced with a different weight fraction of zirconium diboride (ZrB2) particulates (0wt%, 5wt% and 10wt%) to prepare the composite and compare the microstructure and mechanical properties with unreinforced plain alloy. 2. Experimental Procedure In the present study, the AA6063 aluminium alloy was used as a base matrix material and its chemical composition (%) is Si=0.3, Fe=0.35, Mg=0.5, Cu=0.1, Ti=0.1 and the balance is Al. The AA6063 aluminium ingots were melted in an electrical resistance furnace using a graphite crucible. The aluminium melt was overheated upto 850oC. The calculated quantity of halide salts K2ZrF6 and KBF4 as given in Table 1. were incorporated into the aluminium melt to synthesize the ZrB2. The KBF4 organic salt was added in excess of twenty-four percentage of a theoretical mole ratio to avoid the formation of Al3Zr. The melt was stirred erratically for a duration of 1200 seconds. After the execution of the process, the composite mixture was poured into cast iron moulds that are kept ready preheated. Fig. 1 shows the schematic diagram of stir casting setup. The prepared samples were machined and cut so as to prepare the specimens for different studies. As per standard metallographic procedures, the specimens from the cast AMCS were polished and etched with Keller reagents. The microstructure was observed using a scanning electron microscope. Micro hardness studies were carried out for the AA6063 matrix alloy and the prepared composites using Vickers hardness tester. Tensile strength of the base AA6063 matrix alloy and the prepared composites at room temperature (30oC) were determined using INSTRON 100KN UTM 8801. Table 1. The amount of salts added to molten aluminum ZrB2 (Wt% )
0
5
10
K2ZrF6 (g) KBF4 (g)
0 0
104 218
112 233
V. Mohanavel/ Materials Today: Proceedings 5 (2018) 13601–13605
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Figure. 1. Schematic diagram of stir casting setup.
3. Results and discussion 3.1 SEM micrographs Fig. 2(a-b) show the SEM micrographs of AA6063 AMCs containing 5wt%ZrB2 and 10wt%ZrB2 respectively. Microstructural investigations reveal the nearly homogeneous dissemination of ZrB2 particles and also illustrate the reaction free, sharp, stable, clean and clear interface between the AA6063 matrix and the reinforcement. Fig. 2(a-b) display the pure, sharp and clear interface between the matrix and the reinforcement. It should develop the load bearing capacity of the composites. The nearly uniform distribution of ZrB2 reinforcement particles is a prerequisite in enhancing the mechanical properties of a composite [8].
Figure 2. (a-b) SEM micrographs of as-cast AA6063-ZrB2 AMCs with varying wt.% of ZrB2 content. (a) 5wt% and (b) 10wt% ZrB2p content.
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V. Mohanavel/ Materials Today: Proceedings 5 (2018) 13601–13605
3.2 Hardness analysis of AA6063/ZrB2 composites Fig. 3. shows the effect of ZrB2 on the hardness of the AA6063 base matrix alloy and prepared composites. The hardness has been observed to increase with the increase in ZrB2 particles and it is notably greater than the hardness of the base matrix alloy. It may be owing to the presence of hard ZrB2 particles work as obstacles to the indentation, which contributes to enhancing the hardness of the prepared composite. An increase in reinforcement content provides more resistance to plastic deformation, thereby increasing the hardness of the composite [2, 9]. Thus, the AA6063/10wt%ZrB2 composites exhibited higher hardness compared to base matrix alloy.
Figure. 3. Variation of hardness with a weight percentage of ZrB2 addition.
3.3 Tensile strength of the AA6063/ZrB2 composites Tensile strength of the AA6063 matrix alloy and the prepared composites are shown in Fig. 4. The tensile strength of the composites increases linearly with the increase in reinforcement content. It was due to the nearly uniform distribution of ZrB2 and it provides effective transformation of applied tensile load from the matrix to the reinforcement particles. Furthermore, the coefficient of thermal expansion (CTE) mismatch between the AA6063 matrix material and the ZrB2 reinforcement particles generates a huge number of dislocation density around the surface of the reinforcement particles. Thus, ZrB2 particles can effectively serve as a hindrance to dislocation a movement [8, 9]. Thereby it improves the tensile strength of the composites.
Figure. 4. Variation of tensile strength with a weight percentage of ZrB2 addition.
V. Mohanavel/ Materials Today: Proceedings 5 (2018) 13601–13605
13605
4. Conclusions The following conclusions have been made based on the present work: 1.
AA6063 alloys reinforced with ZrB2 composites were excellently prepared through insitu casting process.
2.
SEM microphotographs depict the nearly uniform distribution of ZrB2 particles in the matrix.
3.
Mechanical behavior of the composites change with respect to their weight fraction of reinforcement content. The tensile strength of the composite increases after addition of ZrB2 content. AA6063/10wt.% ZrB2 AMCs show the maximum tensile strength and hardness.
4.
The hardness of the composites was increased from 52HV to 63HV with respect to inclusion of wt.% of ZrB2 particles. The good interfacial bonding of reinforcement particles with the matrix enhances the hardness of the composites.
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. S. Xavier Arockia Raj, Mr. K. Subramani 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] V. Mohanavel, K. Rajan, M. Ravichandran, Synthesis, characterization and properties of stir cast AA6351-aluminium nitride (AlN) composites, Journal of Materials Research, 31 (2016) 3824-3831. [3] S.A. Sajjadi, H.R. Ezatpour, M.T. Parizi, Comparison of microstructure and mechanical properties of A356 aluminum alloy/Al2O3 composites fabricated by stir casting and compo casting processes, Mateials and Design, 34 (2012) 106-111. [4] 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). [5] X.H. Chen, H. Yan, Fabrication of nanosized Al2O3 reinforced aluminum matrix composites by subtype multifrequency ultrasonic vibration, Journal of Materials Research, 30 (2015) 2197-2209. [6] M. Emamy, M. Mahta, J. Rasizadeh, Formation of TiB2 particles during dissolution of TiAl3 in Al-TiB2 metal matrix composite using an in situ technique, Composites Science and Technology, 66 (2006) 1063-1066. [7] Sakip Koksal, Ferit Ficici, Ramazan Kayikci, Omer Savas, Experimental optimization of dry sliding wear behavior of in situ AlB2/Al composite based on Taguchi’s method, Materials and Design, 42 (2012) 124-130. [8] J. David Raja Selvam, I. Dinaharan, In situ formation of ZrB2 particulates and their influence on microstructure and tensile behavior of AA7075 aluminum matrix composites, Engineering Science and Technology, an International Journal, 2016, DOI : 10.1016/j.jestch.2016.09.006, (in press). [9] I. Dinaharan, N. Murugan, Siva Parameswaran, Influence of insitu formed ZrB2 particles on microstructure and mechanical properties of AA6061 metal matrix composites, Materials Science and Engineering A, 528 (2011) 5733-5740. [10] Narendra Kumar, Rakesh Kumar Gautam, Sunil Mohan, In-situ development of ZrB2 particles and their effect on microstructure and mechanical properties of AA5052 metal matrix composites, Materials and Design, 80 (2015) 129-136.
ScienceDirect Materials Today: Proceedings 5 (2018) 13601–13605
www.materialstoday.com/proceedings
ICMMM - 2017
Effect of ZrB2 content on mechanical and microstructural characterization of AA6063 aluminum matrix composites V. Mohanavela*, S. Suresh Kumarb, T. Sathishc, K.T. Anandb b
a Department of Mechanical Engineering, Kingston Engineering College, Vellore, India. Department of Mechanical Engineering, Panimalar Group of Institutions, Chennai, India. c Department of Mechanical Engineering, St. Peter’s University, Chennai, India.
Abstract The in situ AA6063/ZrB2 composite is being widely manufactured by the direct metal reaction technique. The potassium hexafluorozirconate (K2ZrF6) and the potassium tetrafluoroborate (KBF4) were used to synthesize the ZrB2 particles through the salt reaction method. The weight percentage of ZrB2 varied from 0 to 10 in steps of 5. The exothermic reaction between the inorganic salts, K2ZrF6 and KBF4 and the molten aluminium leads to the formation of ZrB2. Micro hardness and tensile strength of the composite were examined. The prepared composites were characterized by scanning electron microscope (SEM). SEM micrographs display that the particles are nearly homogeneous dissemination in the AA6063 matrix alloy. The increase in weight percentage of zirconium diboride particles improves the mechanical properties of the composite. The test results showed that the AA6063/10wt.% of ZrB2 composites had revealed greater hardness and tensile strength than the base matrix.
© 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
Keywords: AA6063 alloy, Ultimate Tensile Strength, Scanning Electron Microscope, ZrB2.
*Corresponding author. Tel : +91 9043392344 E-mail address : [email protected]
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
13602
V. Mohanavel/ Materials Today: Proceedings 5 (2018) 13601–13605
1. Introduction Titanium, aluminium and magnesium alloys are the most popular matrix metals presently in vogue, which are particularly suitable for automobile, defence, structural and aircraft applications [1]. In the last three decades, metal matrix composites (MMCs) 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]. Extensively employed fabrication methods for aluminum matrix composites involve stir casting, compocasting, vacuum casting, powder metallurgy, centrifugal casting, insitu casting and squeeze casting [4-5]. Among those available process, insitu method is most economical and is always preferred. Insitu formed particles reveal strong interfacial bonding with the matrix. Insitu method overcomes the limitations of stir casting process such as improper wetting of reinforcement particles and density dependence of particles and its associated problems like sinking and floating of particles [6]. In situ ceramic particles, such as Al2O3, TiB2, AlN, TiC, B4C and ZrB2 have been widely used as reinforcements in aluminum-based composites [7]. Some research findings on aluminum matrix composites (AMCs) reinforced with ZrB2 particles were stated in the literature [8-10]. David Raja Selvam et al., [8] characterized the mechanical behavior of AA7075/ZrB2 composites fabricated by insitu casting method. They stated that the hardness and tensile strength of the composites are enhanced with the increase in weight percentage of ZrB2 reinforcement content. I. Dinaharan et al., [9] found that the hardness, tensile strength and wear resistance of AA6061/ZrB2 composite enriched as the weight fraction of ZrB2 was increased. Narendra Kumar et al., [10] investigated the influence of ZrB2 particles on microstructure and mechanical properties of AA5052/ZrB2 AMC. They reported that the presence of ZrB2 reinforcement particles enhanced the mechanical behaviors to the composite. From the literature, it is evident that very few information is available on AA6063 alloy based ceramic particles reinforced composites. To the best of our knowledge, no work is done on AA6063/ZrB2 composite. In the present research study, the AA6063 aluminum alloy was reinforced with a different weight fraction of zirconium diboride (ZrB2) particulates (0wt%, 5wt% and 10wt%) to prepare the composite and compare the microstructure and mechanical properties with unreinforced plain alloy. 2. Experimental Procedure In the present study, the AA6063 aluminium alloy was used as a base matrix material and its chemical composition (%) is Si=0.3, Fe=0.35, Mg=0.5, Cu=0.1, Ti=0.1 and the balance is Al. The AA6063 aluminium ingots were melted in an electrical resistance furnace using a graphite crucible. The aluminium melt was overheated upto 850oC. The calculated quantity of halide salts K2ZrF6 and KBF4 as given in Table 1. were incorporated into the aluminium melt to synthesize the ZrB2. The KBF4 organic salt was added in excess of twenty-four percentage of a theoretical mole ratio to avoid the formation of Al3Zr. The melt was stirred erratically for a duration of 1200 seconds. After the execution of the process, the composite mixture was poured into cast iron moulds that are kept ready preheated. Fig. 1 shows the schematic diagram of stir casting setup. The prepared samples were machined and cut so as to prepare the specimens for different studies. As per standard metallographic procedures, the specimens from the cast AMCS were polished and etched with Keller reagents. The microstructure was observed using a scanning electron microscope. Micro hardness studies were carried out for the AA6063 matrix alloy and the prepared composites using Vickers hardness tester. Tensile strength of the base AA6063 matrix alloy and the prepared composites at room temperature (30oC) were determined using INSTRON 100KN UTM 8801. Table 1. The amount of salts added to molten aluminum ZrB2 (Wt% )
0
5
10
K2ZrF6 (g) KBF4 (g)
0 0
104 218
112 233
V. Mohanavel/ Materials Today: Proceedings 5 (2018) 13601–13605
13603
Figure. 1. Schematic diagram of stir casting setup.
3. Results and discussion 3.1 SEM micrographs Fig. 2(a-b) show the SEM micrographs of AA6063 AMCs containing 5wt%ZrB2 and 10wt%ZrB2 respectively. Microstructural investigations reveal the nearly homogeneous dissemination of ZrB2 particles and also illustrate the reaction free, sharp, stable, clean and clear interface between the AA6063 matrix and the reinforcement. Fig. 2(a-b) display the pure, sharp and clear interface between the matrix and the reinforcement. It should develop the load bearing capacity of the composites. The nearly uniform distribution of ZrB2 reinforcement particles is a prerequisite in enhancing the mechanical properties of a composite [8].
Figure 2. (a-b) SEM micrographs of as-cast AA6063-ZrB2 AMCs with varying wt.% of ZrB2 content. (a) 5wt% and (b) 10wt% ZrB2p content.
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V. Mohanavel/ Materials Today: Proceedings 5 (2018) 13601–13605
3.2 Hardness analysis of AA6063/ZrB2 composites Fig. 3. shows the effect of ZrB2 on the hardness of the AA6063 base matrix alloy and prepared composites. The hardness has been observed to increase with the increase in ZrB2 particles and it is notably greater than the hardness of the base matrix alloy. It may be owing to the presence of hard ZrB2 particles work as obstacles to the indentation, which contributes to enhancing the hardness of the prepared composite. An increase in reinforcement content provides more resistance to plastic deformation, thereby increasing the hardness of the composite [2, 9]. Thus, the AA6063/10wt%ZrB2 composites exhibited higher hardness compared to base matrix alloy.
Figure. 3. Variation of hardness with a weight percentage of ZrB2 addition.
3.3 Tensile strength of the AA6063/ZrB2 composites Tensile strength of the AA6063 matrix alloy and the prepared composites are shown in Fig. 4. The tensile strength of the composites increases linearly with the increase in reinforcement content. It was due to the nearly uniform distribution of ZrB2 and it provides effective transformation of applied tensile load from the matrix to the reinforcement particles. Furthermore, the coefficient of thermal expansion (CTE) mismatch between the AA6063 matrix material and the ZrB2 reinforcement particles generates a huge number of dislocation density around the surface of the reinforcement particles. Thus, ZrB2 particles can effectively serve as a hindrance to dislocation a movement [8, 9]. Thereby it improves the tensile strength of the composites.
Figure. 4. Variation of tensile strength with a weight percentage of ZrB2 addition.
V. Mohanavel/ Materials Today: Proceedings 5 (2018) 13601–13605
13605
4. Conclusions The following conclusions have been made based on the present work: 1.
AA6063 alloys reinforced with ZrB2 composites were excellently prepared through insitu casting process.
2.
SEM microphotographs depict the nearly uniform distribution of ZrB2 particles in the matrix.
3.
Mechanical behavior of the composites change with respect to their weight fraction of reinforcement content. The tensile strength of the composite increases after addition of ZrB2 content. AA6063/10wt.% ZrB2 AMCs show the maximum tensile strength and hardness.
4.
The hardness of the composites was increased from 52HV to 63HV with respect to inclusion of wt.% of ZrB2 particles. The good interfacial bonding of reinforcement particles with the matrix enhances the hardness of the composites.
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. S. Xavier Arockia Raj, Mr. K. Subramani 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] V. Mohanavel, K. Rajan, M. Ravichandran, Synthesis, characterization and properties of stir cast AA6351-aluminium nitride (AlN) composites, Journal of Materials Research, 31 (2016) 3824-3831. [3] S.A. Sajjadi, H.R. Ezatpour, M.T. Parizi, Comparison of microstructure and mechanical properties of A356 aluminum alloy/Al2O3 composites fabricated by stir casting and compo casting processes, Mateials and Design, 34 (2012) 106-111. [4] 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). [5] X.H. Chen, H. Yan, Fabrication of nanosized Al2O3 reinforced aluminum matrix composites by subtype multifrequency ultrasonic vibration, Journal of Materials Research, 30 (2015) 2197-2209. [6] M. Emamy, M. Mahta, J. Rasizadeh, Formation of TiB2 particles during dissolution of TiAl3 in Al-TiB2 metal matrix composite using an in situ technique, Composites Science and Technology, 66 (2006) 1063-1066. [7] Sakip Koksal, Ferit Ficici, Ramazan Kayikci, Omer Savas, Experimental optimization of dry sliding wear behavior of in situ AlB2/Al composite based on Taguchi’s method, Materials and Design, 42 (2012) 124-130. [8] J. David Raja Selvam, I. Dinaharan, In situ formation of ZrB2 particulates and their influence on microstructure and tensile behavior of AA7075 aluminum matrix composites, Engineering Science and Technology, an International Journal, 2016, DOI : 10.1016/j.jestch.2016.09.006, (in press). [9] I. Dinaharan, N. Murugan, Siva Parameswaran, Influence of insitu formed ZrB2 particles on microstructure and mechanical properties of AA6061 metal matrix composites, Materials Science and Engineering A, 528 (2011) 5733-5740. [10] Narendra Kumar, Rakesh Kumar Gautam, Sunil Mohan, In-situ development of ZrB2 particles and their effect on microstructure and mechanical properties of AA5052 metal matrix composites, Materials and Design, 80 (2015) 129-136.