Analysis of Mechanical Properties of Aluminium based Metal Matrix Composites Reinforced with Alumina and Sic

Analysis of Mechanical Properties of Aluminium based Metal Matrix Composites Reinforced with Alumina and Sic

Rajan Verma1, Saurabh sharma2, Dinesh Kumar3

123Department Of Mechanical Engineering, Sri Sai College Of Engineering and Technology, Badhani, Pathankot, Punjab, India

Abstract- In the present work, Al356 alloy is taken as base material and then it is reinforced with alumina(Al2o3) and siliconcarbide(sic). The prepared aluminium metal matrix composite samples are in the ratio of Al356:Al2O3=9:1 and Al356:Sic=9:1. The fabrication method used for sample preparation is Stir Casting Process. After Preparation of suitable samples certain tests are performed to analyse various mechanical properties like Tensile strength, Compressive strength, Shear strength, Impact strength and Hardness. After that microstructure of the samples is also observed under microscope. At last, a comparison is made between the mechanical properties of base aluminium alloy and the prepared aluminium metal matrix composites.

Keywords- Al356 alloy, Stir Casting, Al356/Al2O3 aluminium metal matrix composite, Al356/Sic aluminium metal matrix composite.

1. Introduction

   A composite material can be defined as a combination of a matrix and a reinforcement, which when combined gives properties superior to the properties of the individual components. The matrix, normally a form of resin, keeps the reinforcement in the desired orientation. It protects the reinforcement from chemical and environmental attack, and it bonds the reinforcement so that applied loads can be effectively transferred.[1-5]. Composite materials have unique place in manufacturing industry because of their properties such as high strength and stiffness, wear resistance, thermal and mechanical fatigue and creep resistance. Till date a large number of composites have been invented & successfully found their use for different applications. Metal matrix composite (MMCs) is a advancement in production of composites[6]. Metal matrix composites, at present though generating a wide interest in research fraternity, are not as widely in use as their plastic counterparts. High strength, fracture toughness and stiffness are offered by metal matrices than those offered by their polymer counterparts. They can withstand elevated temperature in corrosive environment than polymer composites. Most metals and alloys could be used as matrices and they require reinforcement materials which need to be stable over a range of temperature and non- reactive too. However the guiding aspect for the choice depends essentially on the matrix material. Light metals form the matrix for temperature application and the reinforcements in addition to the aforementioned reasons are characterized by high module[7]. Here, in MMC matrix of metal or alloy & some reinforcement material is used to

   produce composite. Matrix is the base material in the composite. Among the various matrix materials available, aluminium and its alloys are widely used in the production of metal matrix composites. Different aluminium based composites with various reinforcement material have been reported by researchers. Reinforcement of aluminium alloy by hard and soft reinforcements such as SiC, MgO, graphite, Si-rice husk, and many more is continue in research industry and in production in many cases. Wide range of applications and requirement of metal matrix composites in industry for different applications put many researchers in finding a cost effective production methods for these composites[8]. There are different methods for fabrication of composites, depending upon type of material involved and also on type of composite to be produced. Casting is commonly used method in production of MMC. Powder metallurgy is other widely used method for production of MMC. One of the obstacles in wide use of MMC in various applications is its plastic counterparts. But MMCs are preferred in many cases due to High strength; fracture toughness and stiffness are offered by metal matrices than those offered by their polymer counterparts[9].Stir casting technique is mainly used for the fabrication of the composite. Stir casting set-up mainly consists a furnace and a stirring assembly. In general, the solidification synthesis of metal matrix composite involves a melt of the selected matrix material followed by the introduction of a reinforcement material into the melt, obtaining a suitable dispersion. [10-15].

2. Materials and Method

   Al356 alloy which acts as a matrix is taken as the basic material. The detail of composition and properties of the material are as:

   Figure 2.1 Aluminum Alloy Al356 sample.

   1. Chemical composition of Al356 alloy

      Element Wt%

      Cu 0.20

      Mg 0.20 to 0.45

      Mn 0.10

      Si 6.5 to 7.5

      Fe 0.20

      Zn 0.10

      Ti 0.20

      Al Balance

      Table 2.1 Chemical composition of Al356 alloy

   2. Mechanical and Thermal properties of Al356 alloy

   Tensile Strength(MPA) 230

   Hardness(HRC) 55

   Toughness(joule) 6

   2.3.1 Properties of Alumina

   Denisty 3.96g/cc

   Colour Ivory

   Elastic Modulus 370GPa

   Poissons Ratio 0.22

   Vickers Hardness 1365Hv

   Thermal Conductivity 30 W/m-K

   Specific Heat 880 J/kg-K

   Melting Point 2072 0C

   Mean Diameter Size 40µm

   Table 2.3 Properties of Alumina.

   2.3.2 Properties of Silicon Carbide

   Melting point 2200 to 2700

   Hardness 2800(kg/mm2)

   Denisty 3.1(g/cm3)

   Fatique Strength(1×107 MPA) 120 Endurance Limit 56

   Cofficient of Thermal 4.1(µm/m/°C) Expansion

   Modulus of Elasticity 71

   Shear Strength 120

   Latent Heat of Fusion 389kj/kg

   Specific heat 963j/kg

   Liquidus temperature 615oc

   Solidus temperature 555oc

   Table 2.2 Mechanical and Thermal properties of Al356 alloy

   1. Reinforcement Selection

      Many materials can be used as reinforcements with Aluminum alloys which provide strength, hardness, very high resistance to crack propagation, high fracture toughness to the design structure. But it is decided to take Silicon Carbide (SiC) and Aluminum oxide (Al2O3) in powdered form as reinforcement for AMMC. The properties of reinforcement are as:

      Figure 2.2 Aluminium oxide powder (Alumina Powder, Al2O3)

      Figure-2.3 Silicon Carbide (SiC)

      Fracture thoughness 4.6(MPa-m1/2)

      Poissons ratio 0.14

      Colour Black

      Table 2.4 Properties of Silicon Carbide.

   2. Fabrication Methods:

      Stir casting method was used to prepare AMMC of aluminium (Al 356) alloy and reinforcement particles. Reinforcement material (alumina) was first preheated at a temperature of 2500C for 5minutes to improve wettability with matrix forming alloy.The Furnace temperature was set to about maximum 700-750oC in order to minimize the chemical reaction between the substances. Melting of Al356 ingots were performed at a temperature of 750oc and the liquid alloy was then allowed to cool in the furnace to a semi solid state at a temperature of about 6000C. Reinforcement particles (pre-heated) were added to the molten alloy and stirring performed speed of 350 rpm for 10 minutes to reach mushy state. The composite slurry was then superheated to 7200C and a second stirring performed to ensure uniform distribution of alumina particles using a mechanical stirrer was done.

   3. Chemical composition of Al356/Al2O3 AMMC

      Al356/Al2O3 AMMC	Weight of	Weight of Sic	Melting Temp.	Stirrer Speed
      	Al356		(Al356)	(RPM)
      			(60mins)
      10wt% Al2O3	900 grams	100 grams	740-750 0C	350

      Table 2.5 Chemical composition of Al356/Al2O3 AMMC

   4. Chemical composition of Al356/Sic AMMC

   Al356/Sic	Weight	Weight	Melting	Stirrer
   AMMC	of Al356	of Sic	Temp.	Speed
   			(Al356)	(RPM)
   			(60mins)
   10wt% Sic	900 grams	100 grams	740-750 0C	350

   Table 2.6 Chemical composition of Al356/Sic AMMC

   Seven samples are prepared for both Al356/Al2O3 and Al356/SiC AMMC. Similar samples of base Al356 alloy is also prepared.

   Figure 2.4 Al356/Al2O3 and Al356/SiC AMMC.

3. EXPERIMENTAL PROCEDURE

   Figure 3.1 Flow chart of Experimental followed.

   1. Tensile Strength Test

      Tension strength tests were performed on samples machined from the Al 356 alloy composites with dimensions of 6 mm diameter and 36 mm gauge length. Tests were performed by universal testing machine (UTM) linked with computer to facilitate analysis with the help of software. All specimens were test at room temperature.

   2. Hardness Test

      A Rockwell hardness tester machine used for the hardness measurement. The surface being tested generally requires a metallographic finish and it was done with the help of 100, 220, 400, 600 and 1000 grit size emery paper. Load used on Rockwells hardness tester was 250 grams at dwell time 25 seconds for each sample. For hardness testing samples were prepared as per specification required for Brinell hardness Test (i.e. 10mm × 10mm × 25 mm).

   3. Toughness Test

      Toughness of MMC was carried out on Charpy Impact Testing Machine. Four samples with different percentage of reinforcement were prepared. Samples with square cross-section of size (10 × 10 × 55) with single V-notches were prepared.

   4. Microstructure

      Metallurgical Microscope integrated with software operation was used for microstructure examination. As per requirement samples were cut in desired size and prepared for testing using Diamond polishing machine. A series of emery papers of grit sizes ranging from 400m 1500m were used to prepare sample surface for examination.

   5. Compression Test

      Compression tests were used to assess the mechanical behavior of the composites and matrix alloy. The composite and matrix alloy rods were machined to tensile specimens with a diameter of 19mm gauge length of 22 mm. Universal testing machine used for the Compressive Strength measurement.

   6. Shear Test

   Shear tests were used to assess the mechanical behavior of the composites and matrix alloy. The composite and matrix alloy rods were machined to tensile specimens with a diameter of 19mm. Universal testing machine used for the Shear Strength measurement.

4. RESULTS AND DISCUSSIONS

   Tensile Strength

   1. Tensile Test and Yield Strength

      Tensile Strength

      500

      400

      300

      200

      100

      0

      Tensile Strength

      Samples

      Figure 4.1 Comparison the Tensile Strength of Al356 With Al356/10wt%Sic & Al356/10wt% Al2O3

      Figure 4.2 Stress vs. Strain Curves for Al 356 with 10% SiC

      Yield Strength

      Figure 4.3 Stress vs. Strain Curves for Al356 with 10% Al2O3

      Yield Strength

      250

      240

      230

      220

      Yield Strength

      Samples

      Figure 4.4 Comparison the Yield Strength of Al356 With Al356/10wt%Sic & Al356/10wt% Al2O3

      Serial	Composite	Yield	UTS	Elongation
      No.		Strength	(N/mm2)	(%)
      		(N/mm2)
      1	Al 356	230	236	9
      2	10% SiC	248	385	1.98
      3	10 % Al2O3	238	380	2.7

      Table 4.1 Experimental value of UTS, yield Strength and Percentahe Elongation.

   2. HARDNESS TEST

      Hardnesss

      120

      100

      80

      60

      40

      20

      0

      Hardnesss

      Samples

      Hardness

      Figure 4.5 Comparison the Hardness of Al356 , Al356/10wt%Sic & Al356/10wt% Al2O3

      Seri al	Comp osites	Trail		Total Average Hardness Hardness
      no.				(HRC)
      		1	2 3
      1	Al35 6			52
      2	10% SiC	84	85 85	254 84.6
      3	10% Al2O3	99	99 100	298 99.3

      Table 4.2 Experimental value of Hardness.

      In Figure number 4.5 results predict that uniform increase in hardness is also seen. This is due to increase in resistance to deformation by adding SiC and Alumina as reinforcement in Al356.

   3. IMPACT TEST

      As shown in Chart Figure number 4.1 results predict that as	Seria	Composites	Trial			Total	Average
      the reinforcement wt.% UTS is also increases. This happens may be due to dispersion of SiC & Alumina which	l No		1	2	3	force( Nm)	Force(Nm )
      create hinderance to dislocation motion. This may results	1	Al356					6.3
      increase in tensile strength of Al356 alloy. As shown in Figure number 4.4 results predict that as the	2	10% SiC	8.1	9.4	8.5	26	8.6
      reinforcement wt.% Yield Strength is increases. This	3	10 % Al2O3	7	7.8	6.1	20.9	6.9

      happens may be due to dispersion of SiC & Alumina which create hinderance to dislocation motion. To move this defect (plastically deforming or yielding the materal), a larger stress must be applied. This may results increase in tensile strength of reinforced AMMCs.

      Table 4.3 Experimental value of Toughness.

      Impact Strenght(Nm)

      10

      8

      6

      4

      2

      0

      Impact

      Strenght(Nm)

      Samples

      Impact Strength

      Figure 4.6: Comparison of Impact Strength of Al356 with Al356/10wt%Sic & Al356/10wt% Al2O3

      Figure 4.6 shows that with the increase in SiC & Al2O3 constituent Impact strength is increases w.r.t base metal. This is due to proper dispersion of SiC & Al2O3 into the matrix or strong interfacial bonding in between the Al alloy and SiC& Alumina interfaces.

   4. COMPRESSION TEST

      Figure4.7 shows that with the increase in SiC & Al2O3 constituent Impact strength is increases w.r.t base metal. This is due to proper dispersion of SiC & Al2O3 into the matrix or strong interfacial bonding in between the Al alloy and SiC& Alumina interfaces.

   5. SHEAR TEST

      Seri	Composi	Trial			Total	Avera
      al No	tes	1	2	3		ge Shear
      						Streng
      						th
      1	Al356					69
      						MPa
      2	10% SiC	132.	133.	132.	398.	133
      		19	95	13	27	MPa
      3	10 %	126.	123.	122.	372.	124
      	Al2O3	42	67	85	94	MPa

      Table 4.5 Experimental value of Shear Strength.

      Shear Strength

      150

      100

      50

      0

      Shear Strength

      Samples

      Shear Strength

      Ser	Compo	Trial			Total	Average
      ial No	sites	1	2	3		Compressive Strength(Mp
      						a)
      1	Al356					399
      2	10%		423.	424.	422. 1270.	423
      	SiC		62	16	45 23
      3	10	%	439.	441.	438. 1319.	440

      Al2O3 4

      12 75 27

      Figure 4.8 Comparison of Shear Strength of Al356 with, Al356/10wt%Sic & Al356/10wt% Al2O3

      Compressive strength

      450

      440

      430

      420

      410

      400

      390

      Compressive Strength

      Table 4.4 Experimental value of compressive strength.

      Samples

      Compressive

      strength

      380

      370

      Figure 4.7 Comparison of Compressive Strength of Al356 with, Al356/10wt%Sic & Al356/10wt% Al2O3

      As shown in Figure number 4.8 results predict that as the reinforcement wt.% Shear Strength is increases. This happens may be due to dispersion of SiC & Alumina into the matrix.

   6. MICROSRUTURE

   Figure 4.9 Microscopic View of 10 % SiC Reinforced in Al356.

   Figure 4.10 Microscopic View of 10 % Alumina Reinforced in Al356

   Figures 4.9, 4.10 are presented with the microphotographs of Cast Al356-SiC and Alumina composites respectively. Pictures taken under 100x. From figures it can be observed that, the distributions of reinforcements in the respective matrix are fairly uniform. Further these figures reveal the homogeneity of the cast composites. The microphotograph also clearly revels the increased filler contents in the composites, cracks are also seen in the microstructure

5. CONCLUSIONS

   From all above characterizations following conclusions have been drawn:

   1. Tensile Strength increases in both AMMCs as compared to base Al356, but it is more in case of Al356/SiC AMMC .

   2. Yield Strength also increases in both AMMCs as compared to base Al356, but it is more in case of Al356/SiC AMMC.

   3. Hardness also increases in both AMMCs as compared to base Al356, but it is more in case of Al356/Al2O3 AMMC.

   4. Impact Strength also increases in both AMMCs as compared to base Al356, but it is more in case of Al356/SiC AMMC .

   1. Compressive Strength also increases in both AMMCs as compared to base Al356, but it is more in case of Al356/Al2O3 AMMC.

   2. Shear Strength increases in both AMMCs as compared to base Al356, but it is more in case of Al356/SiC AMMC.

   3. From the microstructure pictures it can be observed that, the distributions of reinforcements in the respective matrix are fairly uniform. The microphotograph also clearly revels that with increase in filler contents in the composites, cracks are also seen in the microstructure.

   Thus SiC and alumina as reinforcement for Al356 to form AMMCs, can be utilize in many technologically important applications.

6. SCOPE OF FUTURE WORK

   1. Further reinforcement type, grain size of particles etc can be undertaken for further study with

      same setup.

   2. By change in base metal and stirring rpm new observations can be obtain.

   3. Percentage reinforcement % change can also done to obtain the new results.

7. ACKNOWLEDGEMENT

   After all mighty God, I want to thanks Mr Saurabh sharma (Assistant Professor) , Mr Dinesh Kumar(HOD) and all other staff members of department of mechanical engineering, Sri Sai College Badhani, my mother, beloved father and last but not least to my sisters for their help during my research work.

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