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Preparation and Characterization of ZA27-Alumina-Graphite Reinforced Hybrid Composites
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 18 (2019) 57–65
www.materialstoday.com/proceedings
ICAMME-2018
Preparation and Characterization of ZA27-Alumina-Graphite Reinforced Hybrid Composites Shravan Kumar Yadava*, Karuna Kumar G.a, R.Vijaya Prakashb aDepartment bDepartment
of Mechanical Engineering, Gudlavalleru Engineering College, Krishna-521356,India of Mechanical Engineering, University College of Engineering and Technology,ANU,Guntur-522510,India
Abstract In the present study zinc aluminium based alumina andgraphite particulates MMCs have prepared by using stir casting technique and property analysis has been made. Zinc aluminium and alumina,graphite have been taken as matrix and reinforcement materials respectively. Experiments have been conducted by keeping weight fraction of alumina at 3% and varying weight fraction of graphite (0%, 1%, 3 %,) .And after that by keeping weight fraction of graphite 3% and varying weight fraction of alumina (0%,1%, 3%).Tensile strength and impact strength have been increased. However hardness decreased with dispersion of graphite. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under the responsibility of International Conference on Advances in Materials and Manufacturing Engineering, ICAMME-2018. Keywords: Stir casting, ZA-27, Alumina, Graphite, Hybrid composite.
1. Introduction Now a days zinc-aluminum alloys (ZA alloys) have been widely used for promising material as tribological applications. ZA alloys have become the alternative material primarily for aluminum cast alloys and bronzes due to good cast ability and unique combination of properties. ZA can also be considered as competing materials for cast iron, plastics, and even steel when being applied for operation under conditions of high mechanical loads, moderate sliding speeds and moderate operation temperatures. Interest for extending the practical application of these alloys is based on tribological, economic and ecological reasons. Metal matrix composites (MMCs) reinforced with ceramic particulates show significant performance over pure metals and alloys. MMCs have the best properties of the two components, such as ductility and toughness of the matrix, wear resistance, and strength of the reinforcements. Theseproperties of these materials enable them to be potential for numerous applications such as automotive, aerospace and military industries. S.C. Sharma et al. [1] have reported the lubricated sliding wear behaviour of zinc–aluminium (ZA) alloy. Sandhyarani Biswas et al. [2]have reportedphysical and mechanical properties of alumina (Al2O3) reinforced zinc– aluminium alloy matrix composites by stir casting techniques with varying alumina weight percentages (0 wt. %, ∗
Corresponding author. Tel.: +0-8142506777. E-mail address: [email protected]
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under the responsibility of International Conference on Advances in Materials and Manufacturing Engineering, ICAMME-2018.
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S.K. Yadav et al. / Materials Today: Proceedings 18 (2019) 57–65
4 wt. %, 8 wt. % and 12 wt. %).Y. Radi et al. [3] have revealed microstructure and thermal stability of AZ31 magnesium alloy and its composites, reinforced with 0.5, 1, and 2 wt. % of Al2O3 Nano-particles. Srimant Kumar Mishra et al. [4] have suggested, impact of velocity was the most significant factor followed by filler content while others have relatively less significance on wear rate of ZA-27 metal matrix composites (MMCs) reinforced with silicon carbide (SiC) particles in different weight proportions (0, 3, 6 and 9 wt. %), using Taguchi experimental design.Miroslav Babic et al. [5] have presented the result of tribological property of the ZA-27 alloy reinforced by the Al2O3 particles of sizes 12 and 250μm in quantities of 3.5 and 10 mass %.AlsoK.H.W. Seah et al. [6] have revealed improved mechanical properties of cast ZA-27/graphite particulate composites. Thus by observing above literatures if we want to obtain more better mechanical properties of composite, we have to mix more than one reinforcement materials. In this paper we have added two reinforcement materials graphite, which has solid lubricant property, and alumina, which has highest hardness property. 2. Experimental Methodology 2.1 Materials Used The main reason for selecting the ZA-27 is a good strength alloy with excellent wear resistance & corrosion resistance. Alumina and graphite have taken as reinforcement materials. 2.2 Composites Preparation Stir casting(Fig.1) process is used to fabricate ZA-27 composites. In this process, the base metal was heated about 550°C, above its melting temperature in electric furnace. Therequired quantity of filler particulates (Al2O3) was preheated at 400°C. Because of vortex formation is more responsible for mixing of powder, the molten metal are stirred continuously by using a mechanical stirrer at 450 rpm. When proper vortex in the molten metal then pressure inside is less than upper layer of molten metal at this time the alumina powder and graphite were mixed.After reinforcement of powders, ZA-27 molten metal was stirred at speed of 450 rpm for 4-5 min in order to get uniform mixing of filler particulates in the matrix material. The molten metal was then poured into permanent casting die. After solidification, castings are taken out from the permanent die(Fig.2), and are cut to the required shape and sizes. Die, and stirrer were preheated before reinforcement to remove sudden temperature effect.
Fig.1 Stir casting equipment
Fig.2 Die for pouring molten metal
Fig.3 Composites obtained after casting
2.3 Preparation of Specimens for Testing The products obtained after casting(Fig.3) are taken and machined on the lathe and shaper machines. For performing the various tests on various machines we have prepared the specimens of required dimensions and shapes based on the suitable requirements of the machines. 2.3.1 Toughness Testing For performing of toughness test(Fig.5), the specimens were made of sizes of 10 ൈ10 mm2and 55 mm length on shaper machine and charpy test was being performed. In this test swinging head strikes other side of specimen notch. Pendulum falls from 1.457 heights at an angle of 1400 and the weight of hammer was 250N. The pendulum
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impact testing machine(Fig.4) ascertains the notch impact strength of the material by shattering the V-notched specimen with a pendulum hammer, measuring the spent energy and relating it to the cross section of the specimen.
Fig.4 Impact testing machine
Fig.5 Samples for Toughness Testing
2.3.2Tensile Testing For performing of tensile test we have prepared the specimens(Fig.7) of length 200 mm long and 18mm diameter. To perform this test we have changed the dimensions of above obtained specimen to standard ASTM dimensions for performing tensile test for different compositions. Tensile properties of the composites were analyzed by carrying out test on the Universal testing machine(Fig.6). During the tests, the load elongation datas were captured by induced software, whose datas were used for further analysis. The tensile test was generally performed on round specimens. During the test a uni-axial load was applied through both the ends of the specimen.
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Fig.6 Universal Testing Machine
Fig.7 Samples for Tensile Testing
2.3.3 Hardness Measurement For performing Rockwell hardness test technique(Fig.8) the specimens of diameter 18 mm is prepared and they are polished neatly by using emery papers. The hardness of the composite specimens(Fig.9) was measured by using Rockwell hardness tester. Microhardness of all the samples was measured under a load of 30kgf for a dwell time of 5 seconds. For each specimen measurements were taken.
Fig.8Rockwell hardness testing machine
Fig.9 Samples for Hardness Testing
S.K. Yadav et al. / Materials Today: Proceedings 18 (2019) 57–65
61
3. Results and Discussion 3.1 Microstructures
Fig.10Pure ZA
Fig.11 Alumina3%+Gr0%
Fig.12 Alumina3%+Gr1%
Fig.13 Alumina0%+Gr3%
Fig.14 Alumina1%+Gr3%
Fig.15Alumina3%+Gr3%
The microstructures of the compositions are given in the above figures(Fig.10 to Fig.15) and we can absorve the variation in the structure because of mixing filler materials. Pre-heating of the fillers avoids the blow hole formation and the dendride formation in the structure is due to stirring at required speeds which increases the bonding nature, by that we can increase the strength of the composite. The uniform distribution of the filler materials due to mixing them after the formation of vortex in the molten metal.
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3.2Toughness Study Table 1: Toughness of ZA 27with 3wt% fixed alumina and varying graphite. Material
Alumina inwt%
Graphite inwt%
Toughness in j/mm2
Toughness improvement in %
ZA 27
0
0
3.5
-
ZA 27
3
0
3.65
4.28
ZA 27
3
1
3.8
8.57
ZA 27
3
3
3.9
11.42
Table 2: Toughness of ZA 27with 3wt% fixed graphite and varying Alumina. Material
Alumina inwt%
Graphite in wt%
Toughness in j/mm2
Toughness improvement in %
ZA 27
0
0
3.5
-
ZA 27
0
3
3.6
2.85
ZA 27
1
3
3.74
6.85
ZA 27
3
3
3.9
11.42
Fig.16 Graph of toughness Vs wt. % of alumina and graphite
From the tables 1, 2 and fig.16 we can see that the impact energies of the composites increase when mixed with alumina and graphite particulates and increasing more as wt% of reinforced particles increased. Srimant Kumar Mishra et al.[4] also reported the increasing tendency of impact energy for silicon carbide particle filled ZA-27 MMCs. Here it is seen that the impact energies of the composites increase more when mixed with alumina as compared to mixing with graphite.
S.K. Yadav et al. / Materials Today: Proceedings 18 (2019) 57–65
63
3.3 Tensile Strength Table 3: Tensile-ultimate stress of ZA -27 with fixed 3% alumina and varying graphite. Material
Alumina inwt%
Graphite in wt%
Tensile-ultimate stress (N/mm2)
Stress improvement in %
ZA 27
0
0
308.7
-
ZA 27
3
0
353.5
14.51
ZA 27
3
1
401.27
29.98
ZA 27
3
3
482.3
56.23
Table 4: Tensile-ultimate stress of ZA 27with fixed 3% graphite and varying alumina. Material
Alumina inwt%
Graphite in wt%
Tensile-ultimate stress (N/mm2)
Stress improvement in %
ZA 27
0
0
308.7
-
ZA 27
0
3
326.4
5.73
ZA 27
1
3
348.6
12.92
ZA 27
3
3
482.3
56.23
From the tables 3,4 and fig.17 we can see that in all the samples the tensile strength of the composites increases with increase in filler content.K.H.W. Seahet al.[6] also reported the similar increasing tendency of tensile strength for cast ZA-27/graphite particulate composites. Due to the presence of hard particulates, the load on the matrix has transferred to the reinforcing elements and increased the load bearing capability of the composites. That’s why we can say that increase in weight percentage of the filler material, more load has transferred to reinforcement which leads to increase in tensile strength. But when we add further graphite to the matrix there is decreasing of the tensile strength due to the softness of graphite.
Fig.17 Graph of tensile strength Vs wt. % of alumina and graphite
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3.4 Rockwell Hardness Study Table 5:Hardness of ZA 27with fixed 3wt% alumina and varying graphite. Material
Alumina inwt%
Graphite in wt%
Rockwell hardness
Hardness improvement in %
ZA 27
0
0
57.33
-
ZA 27
3
0
73.33
27.85
ZA 27
3
1
68.4
19.30
ZA 27
3
3
65.9
14.94
Table 6: Hardness of ZA 27with fixed 3wt% graphite and varying alumina. Material
Alumina inwt%
Graphite in wt%
Rockwell hardness
Hardness improvement in %
ZA 27
0
0
57.33
-
ZA 27
0
3
53
-7.5
ZA 27
1
3
63.33
10.46
ZA 27
3
3
65.9
14.94
Fig.18Rockwell hardness Vs wt. % of alumina and graphite
From the table 5 and fig.18it can be seen that as the graphite content increases, the hardness of the composite materials decreases due to softness of graphite. K.H.W. Seahet al.[6] also reported the similar results for cast ZA27/graphite particulate composites. But still there is improved % of hardness as compared to pure ZA-27 due to presence of hard particles of alumina. From table 6 and fig.18it can be observed as the alumina content increases, the hardness of the composite materials increases due to hardness of alumina particulate.Srimant Kumar Mishra et al.[4] also reported the increasing tendency of hardness for silicon carbide particle filled ZA-27 MMCs.
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Conclusions
ZA27-Alumina-Graphite Reinforced Hybrid Composites have successfully fabricated by stir casting technique.
Tensile strength of prepared composites is higher in case of composites, when compared to cast ZA 27.
Addition of 3wt% Al2O3 increases the tensile strength considerably with respect to base matrix ZA 27. Whereas the addition of Gr particulates doesn’t vary the tensile strength much with respect to Al2O3 added composition.
Hardness of the prepared composites is higher than the base ZA 27 alloy.
Addition of 3wt% Al2O3 increases hardness considerably. Whereas the addition of Graphite particulates decreases the hardness, but is higher than the ZA 27alloy.
Particulates Toughness of the composite has been increased by the addition of Al2O3 and graphite.
References [1] S.C. Sharma, B.M. Girish, Rathnakar Kamath, B.M. Satish. Sliding wear behavior of zircon particles reinforced ZA- 27 alloy composite materials, Wear 224. (1999.), 89-94. [2] Sandhyarani Biswas et al., Thermo-mechanical and crack position on stress intensity factor in particle-reinforced Zinc–aluminium alloy composites. Computational Materials Science 55 (2012). [3] Y. Radi et al. Effect of Al2O3 Nano-particles on the microstructural stability of AZ31 Mg alloy after equal channel angular pressing. Materials Science and Engineering A 527 (2010) 2764–2771. [4] Srimant Kumar Mishra et al., A study on processing, characterization and erosion wear behaviour of silicon carbide particle filled ZA-27 metal matrix composites,Materials and design 55(2014) 958-965. [5] Miroslav Babic, SlobodanMitrovic´FatimaZivic. Effects of Al2O3 particle reinforcement on the lubricated sliding wear behaviour of ZA-27 alloy composites. J Mater Sci (2011) 46:6964–6974. [6] K.H.W. Seah et al., Mechanical properties of cast ZA-27/graphite particulate composites. Materials and Design vol.16 No.5, 1995.
ScienceDirect Materials Today: Proceedings 18 (2019) 57–65
www.materialstoday.com/proceedings
ICAMME-2018
Preparation and Characterization of ZA27-Alumina-Graphite Reinforced Hybrid Composites Shravan Kumar Yadava*, Karuna Kumar G.a, R.Vijaya Prakashb aDepartment bDepartment
of Mechanical Engineering, Gudlavalleru Engineering College, Krishna-521356,India of Mechanical Engineering, University College of Engineering and Technology,ANU,Guntur-522510,India
Abstract In the present study zinc aluminium based alumina andgraphite particulates MMCs have prepared by using stir casting technique and property analysis has been made. Zinc aluminium and alumina,graphite have been taken as matrix and reinforcement materials respectively. Experiments have been conducted by keeping weight fraction of alumina at 3% and varying weight fraction of graphite (0%, 1%, 3 %,) .And after that by keeping weight fraction of graphite 3% and varying weight fraction of alumina (0%,1%, 3%).Tensile strength and impact strength have been increased. However hardness decreased with dispersion of graphite. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under the responsibility of International Conference on Advances in Materials and Manufacturing Engineering, ICAMME-2018. Keywords: Stir casting, ZA-27, Alumina, Graphite, Hybrid composite.
1. Introduction Now a days zinc-aluminum alloys (ZA alloys) have been widely used for promising material as tribological applications. ZA alloys have become the alternative material primarily for aluminum cast alloys and bronzes due to good cast ability and unique combination of properties. ZA can also be considered as competing materials for cast iron, plastics, and even steel when being applied for operation under conditions of high mechanical loads, moderate sliding speeds and moderate operation temperatures. Interest for extending the practical application of these alloys is based on tribological, economic and ecological reasons. Metal matrix composites (MMCs) reinforced with ceramic particulates show significant performance over pure metals and alloys. MMCs have the best properties of the two components, such as ductility and toughness of the matrix, wear resistance, and strength of the reinforcements. Theseproperties of these materials enable them to be potential for numerous applications such as automotive, aerospace and military industries. S.C. Sharma et al. [1] have reported the lubricated sliding wear behaviour of zinc–aluminium (ZA) alloy. Sandhyarani Biswas et al. [2]have reportedphysical and mechanical properties of alumina (Al2O3) reinforced zinc– aluminium alloy matrix composites by stir casting techniques with varying alumina weight percentages (0 wt. %, ∗
Corresponding author. Tel.: +0-8142506777. E-mail address: [email protected]
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under the responsibility of International Conference on Advances in Materials and Manufacturing Engineering, ICAMME-2018.
58
S.K. Yadav et al. / Materials Today: Proceedings 18 (2019) 57–65
4 wt. %, 8 wt. % and 12 wt. %).Y. Radi et al. [3] have revealed microstructure and thermal stability of AZ31 magnesium alloy and its composites, reinforced with 0.5, 1, and 2 wt. % of Al2O3 Nano-particles. Srimant Kumar Mishra et al. [4] have suggested, impact of velocity was the most significant factor followed by filler content while others have relatively less significance on wear rate of ZA-27 metal matrix composites (MMCs) reinforced with silicon carbide (SiC) particles in different weight proportions (0, 3, 6 and 9 wt. %), using Taguchi experimental design.Miroslav Babic et al. [5] have presented the result of tribological property of the ZA-27 alloy reinforced by the Al2O3 particles of sizes 12 and 250μm in quantities of 3.5 and 10 mass %.AlsoK.H.W. Seah et al. [6] have revealed improved mechanical properties of cast ZA-27/graphite particulate composites. Thus by observing above literatures if we want to obtain more better mechanical properties of composite, we have to mix more than one reinforcement materials. In this paper we have added two reinforcement materials graphite, which has solid lubricant property, and alumina, which has highest hardness property. 2. Experimental Methodology 2.1 Materials Used The main reason for selecting the ZA-27 is a good strength alloy with excellent wear resistance & corrosion resistance. Alumina and graphite have taken as reinforcement materials. 2.2 Composites Preparation Stir casting(Fig.1) process is used to fabricate ZA-27 composites. In this process, the base metal was heated about 550°C, above its melting temperature in electric furnace. Therequired quantity of filler particulates (Al2O3) was preheated at 400°C. Because of vortex formation is more responsible for mixing of powder, the molten metal are stirred continuously by using a mechanical stirrer at 450 rpm. When proper vortex in the molten metal then pressure inside is less than upper layer of molten metal at this time the alumina powder and graphite were mixed.After reinforcement of powders, ZA-27 molten metal was stirred at speed of 450 rpm for 4-5 min in order to get uniform mixing of filler particulates in the matrix material. The molten metal was then poured into permanent casting die. After solidification, castings are taken out from the permanent die(Fig.2), and are cut to the required shape and sizes. Die, and stirrer were preheated before reinforcement to remove sudden temperature effect.
Fig.1 Stir casting equipment
Fig.2 Die for pouring molten metal
Fig.3 Composites obtained after casting
2.3 Preparation of Specimens for Testing The products obtained after casting(Fig.3) are taken and machined on the lathe and shaper machines. For performing the various tests on various machines we have prepared the specimens of required dimensions and shapes based on the suitable requirements of the machines. 2.3.1 Toughness Testing For performing of toughness test(Fig.5), the specimens were made of sizes of 10 ൈ10 mm2and 55 mm length on shaper machine and charpy test was being performed. In this test swinging head strikes other side of specimen notch. Pendulum falls from 1.457 heights at an angle of 1400 and the weight of hammer was 250N. The pendulum
S.K. Yadav et al. / Materials Today: Proceedings 18 (2019) 57–65
59
impact testing machine(Fig.4) ascertains the notch impact strength of the material by shattering the V-notched specimen with a pendulum hammer, measuring the spent energy and relating it to the cross section of the specimen.
Fig.4 Impact testing machine
Fig.5 Samples for Toughness Testing
2.3.2Tensile Testing For performing of tensile test we have prepared the specimens(Fig.7) of length 200 mm long and 18mm diameter. To perform this test we have changed the dimensions of above obtained specimen to standard ASTM dimensions for performing tensile test for different compositions. Tensile properties of the composites were analyzed by carrying out test on the Universal testing machine(Fig.6). During the tests, the load elongation datas were captured by induced software, whose datas were used for further analysis. The tensile test was generally performed on round specimens. During the test a uni-axial load was applied through both the ends of the specimen.
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Fig.6 Universal Testing Machine
Fig.7 Samples for Tensile Testing
2.3.3 Hardness Measurement For performing Rockwell hardness test technique(Fig.8) the specimens of diameter 18 mm is prepared and they are polished neatly by using emery papers. The hardness of the composite specimens(Fig.9) was measured by using Rockwell hardness tester. Microhardness of all the samples was measured under a load of 30kgf for a dwell time of 5 seconds. For each specimen measurements were taken.
Fig.8Rockwell hardness testing machine
Fig.9 Samples for Hardness Testing
S.K. Yadav et al. / Materials Today: Proceedings 18 (2019) 57–65
61
3. Results and Discussion 3.1 Microstructures
Fig.10Pure ZA
Fig.11 Alumina3%+Gr0%
Fig.12 Alumina3%+Gr1%
Fig.13 Alumina0%+Gr3%
Fig.14 Alumina1%+Gr3%
Fig.15Alumina3%+Gr3%
The microstructures of the compositions are given in the above figures(Fig.10 to Fig.15) and we can absorve the variation in the structure because of mixing filler materials. Pre-heating of the fillers avoids the blow hole formation and the dendride formation in the structure is due to stirring at required speeds which increases the bonding nature, by that we can increase the strength of the composite. The uniform distribution of the filler materials due to mixing them after the formation of vortex in the molten metal.
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3.2Toughness Study Table 1: Toughness of ZA 27with 3wt% fixed alumina and varying graphite. Material
Alumina inwt%
Graphite inwt%
Toughness in j/mm2
Toughness improvement in %
ZA 27
0
0
3.5
-
ZA 27
3
0
3.65
4.28
ZA 27
3
1
3.8
8.57
ZA 27
3
3
3.9
11.42
Table 2: Toughness of ZA 27with 3wt% fixed graphite and varying Alumina. Material
Alumina inwt%
Graphite in wt%
Toughness in j/mm2
Toughness improvement in %
ZA 27
0
0
3.5
-
ZA 27
0
3
3.6
2.85
ZA 27
1
3
3.74
6.85
ZA 27
3
3
3.9
11.42
Fig.16 Graph of toughness Vs wt. % of alumina and graphite
From the tables 1, 2 and fig.16 we can see that the impact energies of the composites increase when mixed with alumina and graphite particulates and increasing more as wt% of reinforced particles increased. Srimant Kumar Mishra et al.[4] also reported the increasing tendency of impact energy for silicon carbide particle filled ZA-27 MMCs. Here it is seen that the impact energies of the composites increase more when mixed with alumina as compared to mixing with graphite.
S.K. Yadav et al. / Materials Today: Proceedings 18 (2019) 57–65
63
3.3 Tensile Strength Table 3: Tensile-ultimate stress of ZA -27 with fixed 3% alumina and varying graphite. Material
Alumina inwt%
Graphite in wt%
Tensile-ultimate stress (N/mm2)
Stress improvement in %
ZA 27
0
0
308.7
-
ZA 27
3
0
353.5
14.51
ZA 27
3
1
401.27
29.98
ZA 27
3
3
482.3
56.23
Table 4: Tensile-ultimate stress of ZA 27with fixed 3% graphite and varying alumina. Material
Alumina inwt%
Graphite in wt%
Tensile-ultimate stress (N/mm2)
Stress improvement in %
ZA 27
0
0
308.7
-
ZA 27
0
3
326.4
5.73
ZA 27
1
3
348.6
12.92
ZA 27
3
3
482.3
56.23
From the tables 3,4 and fig.17 we can see that in all the samples the tensile strength of the composites increases with increase in filler content.K.H.W. Seahet al.[6] also reported the similar increasing tendency of tensile strength for cast ZA-27/graphite particulate composites. Due to the presence of hard particulates, the load on the matrix has transferred to the reinforcing elements and increased the load bearing capability of the composites. That’s why we can say that increase in weight percentage of the filler material, more load has transferred to reinforcement which leads to increase in tensile strength. But when we add further graphite to the matrix there is decreasing of the tensile strength due to the softness of graphite.
Fig.17 Graph of tensile strength Vs wt. % of alumina and graphite
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S.K. Yadav et al. / Materials Today: Proceedings 18 (2019) 57–65
3.4 Rockwell Hardness Study Table 5:Hardness of ZA 27with fixed 3wt% alumina and varying graphite. Material
Alumina inwt%
Graphite in wt%
Rockwell hardness
Hardness improvement in %
ZA 27
0
0
57.33
-
ZA 27
3
0
73.33
27.85
ZA 27
3
1
68.4
19.30
ZA 27
3
3
65.9
14.94
Table 6: Hardness of ZA 27with fixed 3wt% graphite and varying alumina. Material
Alumina inwt%
Graphite in wt%
Rockwell hardness
Hardness improvement in %
ZA 27
0
0
57.33
-
ZA 27
0
3
53
-7.5
ZA 27
1
3
63.33
10.46
ZA 27
3
3
65.9
14.94
Fig.18Rockwell hardness Vs wt. % of alumina and graphite
From the table 5 and fig.18it can be seen that as the graphite content increases, the hardness of the composite materials decreases due to softness of graphite. K.H.W. Seahet al.[6] also reported the similar results for cast ZA27/graphite particulate composites. But still there is improved % of hardness as compared to pure ZA-27 due to presence of hard particles of alumina. From table 6 and fig.18it can be observed as the alumina content increases, the hardness of the composite materials increases due to hardness of alumina particulate.Srimant Kumar Mishra et al.[4] also reported the increasing tendency of hardness for silicon carbide particle filled ZA-27 MMCs.
S.K. Yadav et al. / Materials Today: Proceedings 18 (2019) 57–65
65
Conclusions
ZA27-Alumina-Graphite Reinforced Hybrid Composites have successfully fabricated by stir casting technique.
Tensile strength of prepared composites is higher in case of composites, when compared to cast ZA 27.
Addition of 3wt% Al2O3 increases the tensile strength considerably with respect to base matrix ZA 27. Whereas the addition of Gr particulates doesn’t vary the tensile strength much with respect to Al2O3 added composition.
Hardness of the prepared composites is higher than the base ZA 27 alloy.
Addition of 3wt% Al2O3 increases hardness considerably. Whereas the addition of Graphite particulates decreases the hardness, but is higher than the ZA 27alloy.
Particulates Toughness of the composite has been increased by the addition of Al2O3 and graphite.
References [1] S.C. Sharma, B.M. Girish, Rathnakar Kamath, B.M. Satish. Sliding wear behavior of zircon particles reinforced ZA- 27 alloy composite materials, Wear 224. (1999.), 89-94. [2] Sandhyarani Biswas et al., Thermo-mechanical and crack position on stress intensity factor in particle-reinforced Zinc–aluminium alloy composites. Computational Materials Science 55 (2012). [3] Y. Radi et al. Effect of Al2O3 Nano-particles on the microstructural stability of AZ31 Mg alloy after equal channel angular pressing. Materials Science and Engineering A 527 (2010) 2764–2771. [4] Srimant Kumar Mishra et al., A study on processing, characterization and erosion wear behaviour of silicon carbide particle filled ZA-27 metal matrix composites,Materials and design 55(2014) 958-965. [5] Miroslav Babic, SlobodanMitrovic´FatimaZivic. Effects of Al2O3 particle reinforcement on the lubricated sliding wear behaviour of ZA-27 alloy composites. J Mater Sci (2011) 46:6964–6974. [6] K.H.W. Seah et al., Mechanical properties of cast ZA-27/graphite particulate composites. Materials and Design vol.16 No.5, 1995.