Mechanical Properties of Al-Cu Alloy with Sic, Graphite and Fly Ash Composite Material

Mechanical Properties of Al-Cu Alloy with Sic, Graphite and Fly Ash Composite Material

Srinivasan Vishwanath 1

1. Student, Department of Mechanical Engineering, VVIT, Bangalore Karnataka, India1

   Annoji Rao T. M. 2

   Associate Professor, Department of Mechanical Engineering, VVIT ,Bangalore Karnataka, India2

   Abstract Metal matrix composites (MMCs) are engineered materials, formed by the combination of two or more dissimilar materials (at least one of which is a metal) to obtain enhanced properties. In the present investigation, anAl4.5% Cu alloy was used as the matrix and fly ash as the filler material, graphite is reinforcement. In the present, aerospace, automobile industries, replacing the existing metal matrix composites from Al 6061 to its high performance application. Aluminum copper alloy matrix composite attracts the much attention due to their lightness, high thermal conductivity, moderate casting temperature etc. fly ash and graphite powders are used because of its high strength, high hardness, less density.The composite was produced using stir casting method. The fly ash was added in 3%, 6%, and 9 wt. % and graphite was added in 3%, 6%, and 9 wt. % to the molten metal. The composite was tested for fluidity, hardness, density, mechanical properties, Microstructure examination was done using a scanning electron microscope to obtain the distribution of fly ash and graphite in the aluminium matrix. The results show an increase in hardness, tensile strength with increasing the fly ash and graphite content. The density decreases with increasing fly ash content. Corrosion increases with increasing fly ash content. Specimen is fabricated at different weight percentages and to be carried out for mechanical properties.

   Keywords Aluminium, Composite ,Fly ash, Graphite, Matrix

   1. INTRODUCTION

      Traditional materials do not always provide the necessary properties under all service conditions. Metal matrix composites (MMCs) are advanced materials resulting from a combination of two or more materials (one of which is a metal and the other a non-metal) in which tailored properties are realized. They have received considerable attention in recent years due to their high strength, stiffness, and low density. Data related to mechanical properties, microstructure, etc., have been cited in the literature. A variety of particles such as mica, Al2O3, graphite, and SiC have been used as reinforcement materials with aluminium alloys [48] as the matrices. It appears that stir casting is one of the methods for producing composites[1-7]. The use of fly ash as a reinforcement material [9] results in improvement of mechanical properties of the composite. Fly ash was separated into cenosphere and precipitator fly ash. The use of precipitator fly ash in aluminium decreases the density of composites and increases their wear resistance[12].. It was found that fly ash particles lead to an enhanced pitting corrosion of the composite in comparison to unreinforced matrix.[10-14] In the present investigation, Al4.5% Cu alloy with fly ash (as

      received from a thermal power plant) as particulates were successfully fabricated using the stir casting method. Mechanical properties of the MMCs were investigated

   2. EXPERIMENTAL

      Aluminium with 4.5% Cu was selected as the matrix material. The chemical composition, analysed by a Bairdas DV-6S optical emission spectrometer, is given in Table 1. Fly ash was used as the reinforcement and its composition is given in Table 2.The average particle size was found to be 10 m. The density of fly ash was found to be 2.09 g/cm3. Fig. 1 shows SEM micrographs of fly ash particulates.

      Table 1. Chemical composition of Al4.5% Cu alloy

      Cu	Mg	Si	Fe	Mn	Ti	Zn	Al
      4.5	1.00	0.60	0.65	0.10	0.10	0.20	Balance

      Table 2. Chemical composition of fly ash in weight Percentages

      Al2o3	Sio2	Fe2o3	Tio2	Loss on ignition
      30.40	58.41	8.44	2.75	1.43

      The synthesis of the composite was carried out by stir casting. The ingots of Al4.5% Cu alloy were taken in a graphite crucible and melted in an electric furnace .The temperature was slowly raised to 850 °C. The melt was degassed at 800 °C using a solid dry hexachloroethane (C2Cl6, 0.5 wt. %) degasser. The molten metal was stirred to create a vortex and the particulates were introduced. The degassed molten metal was placed below the stirrer and stirred at approximately 500 rpm. The preheated fly ash particles were slowly added into the melt. Small pieces of Mg chips (0.5 wt. %) were added to the molten metal to ensure good wettability of particles with the molten metal. The percentage of fly ash added 3, 6, and 9 wt. % also the percentage of graphite added was 3, 6, and 9 wt. %. The stirred dispersed molten metal was poured into preheated

      S.G. iron moulds 25, 37,and 50 in diameter and 200 mm height, and cooled to room temperature.

      Fig. 1. SEM of fly ash particulates

      Composites produced were subjected to solutionisation and age hardening (T6). The castings were heated to 525 °C and held for 17 hours, quenched in warm water, then reheated to 175 °C and held for 18 hours. They were sectioned and test samples were prepared for various tests. The densities of the specimens were measured using the Archimedes principle. Their hardness was determined using the Brinnel hardness tester. The load of 250 kg using a 5 mm steel ball indenter was used to measure the hardness. The microstructure of the MMCs was observed under a scanning electron microscope (SEM) at various locations across the specimen to examine the distribution of fly ash and graphite in the matrix. Tensile strengths is determined using a 20 kN computerized UTM with an electronic extensometer as per ASTM E-8 standards. Online plotting of load versus extension was done continuously through a data acquisition system.

   3. RESULTS AND DISCUSSION

3.1. Tensile Properties

Table 2 shows the variation of tensile strength of the composites with the different weight fractions of fly ash and graphite particles. It can be noted that the tensile strength increased with an increase in the weight percentage of fly ash and graphite. Therefore the fly ash particles act as barriers to the dislocations when taking up the load applied (1-4). The hard fly ash particles obstruct the advancing dislocation front, thereby strengthening the matrix (2-6). However, as the size of the fly ash particles increased, there was decrease in tensile strength. Good bonding of smaller size fly ash particles with the matrix is the reason for this behavior. The observed improvement in tensile strength of the composite is attributed to the fact that the filler fly ash and graphite posses higher strength and toughness.

1. Testing for Mechanical Properties

   Table 3 shows the tensile test result of 25mm diameter rod, 37 mm diameter & 50mm diameter

   Composition %	Peak		load(KN)	Tensile Strength(N/mm2)
   	Dia 25 mm	Dia 37 mm	Dia5 0m m	Dia2 5m m	Dia 37 mm	Dia 50 mm
   Flyash 3%			15.5
   	21.9			181.	145.1
   Graphite 3%		16.10	0			105.88
   	0			98	0
   Flyash 3%	10.2		14.5	161.	149.9
   		18.40				189.88
   Graphite 6%	0		0	67	2
   Flyash 3%	14.8			119.	119.3
   		11.80	8.30			200.52
   Graphite 9%	0			4	3
   Flyash 6%	18.4		11.5	149.
   		17.40			183.4	95.94
   Graphite 3%	0		0	92
   Flyash 6%	18.9			152.	180.9
   		20.20	7.40			128.33
   Graphite 6%	0			52	9
   Flyash 6%	17.3			171.	260.3
   		26.90	9.80			154.96
   Graphite 9%	0			57	0
   Flyash 9%	12.3		15.2	101.	171.5
   		17.30				143.46
   Graphite 3%	0		0	68	7
   Flyash 9%	11.8		15.4	119.	181.9
   		21.90				201.25
   Graphite 6%	0		0	33	8
   Flyash 9%	12.2		11.0	101.	206.9
   		24.00				201.28
   Graphite 9%	3		0	23	7

   1. (d)

   2. (e)

(f)

Fig. 2. Tensile properties of composites (a) Tensile strength v/s % of graphite in 25mm diameter(b) Tensile strength v/s

% of Fly ash in 25mm diameter(c) Tensile strength v/s % of graphite in 37mm diameter(d) Tensile strength v/s % of

Fly ash in 37mm diameter(e)Tensile strength v/s % of graphite in 50 mm(f) Tensile Strength v/s % of Fly ash in 50mm diameter

1. Hardness

   From Table.4, it can be noted that the hardness of the composite increased with the increase in weight fraction of the fly ash and graphite particles. Thus the hard fly ash

   particles help in increasing the hardness of the Aluminum alloy (Al6061) matrix

   Table 4 shows the hardness test result of 25mmdia, 37mmdia and 50 mm dia

   Sl no	Composition %	Ball Diameter D (mm)	Load F (kgf)	Diameter 25mm		Diameter 37mm		Diameter 50mm
   				Mean diameter of indentation d (mm)	Brinell hardness number (kgf/mm2)	Mean diameter of indentation d (mm)	Brinell hardness number (kgf/mm2)	Mean diameter of indentation d (mm)	Brinell hardness number (kgf/mm2)
   1	Flyash 3% Graphite 3%	5	250	2.26	59	1.76	98.96	1.8	95
   2	Flyash 3% Graphite 6%	5	250	2.10	68	1.7	107.65	1.65	113.95
   3	Flyash 3% Graphite 9%	5	250	1.96	79	1.63	116.31	1.55	138.74
   4	Flyash 6% Graphite 3%	5	250	1.84	82	1.8	95	1.9	84.86
   5	Flyash 6% Graphite 6%	5	250	1.80	95	1.73	102.933	1.7	108
   6	Flyash 6% Graphite 9%	5	250	1.75	101	1.7	106.90	1.5	138.49
   7	Flyash 9% Graphite 3%	5	250	1.74	102	1.76	98.96	1.7	95
   8	Flyash 9% Graphite 6%	5	250	1.72	104	1.63	116.33	1.55	129.60
   9	Flyash 9% Graphite 9%	5	250	1.70	106	1.6	121	1.55	129.74

   1. (b)

   2. (d)

(e) (f)

Fig. 3. Hardness properties of composites (a) Brinell Hardness Number v/s % of graphite Test results of 25mm diameter (b) Brinell Hardness Number v/s % of Flyash Test results of 25mm diameter (c) Brinell Hardness Number v/s % of graphite Test results of 37mm diameter (d) Brinell Hardness Number v/s % of Flyash Test results of 37mm diameter (e) Brinell Hardness Number v/s % of graphite Test results of 50mm diameter (f) Brinell Hardness Number v/s % of Flyash Test results of 50mm diameter

1. Microstructure

   Fly ash

   Fly ash

   Fly ash

   As the microstructure plays an important role in the overall performance of a composite and the physical properties depend on the microstructure, reinforcement particle size,

   shape and distribution in the alloy, prepared samples were examined using fly ash and graphite particulates can be seen in the SEM photomicrograph

   Graphite

   Graphite

   Graphite

   Fly ash

   Graphite

   Fly ash

   1. (b) (c)

      Graphite

      Fly ash

      Graphite

      (d) (e) (f)

      Fig. 4 SEM photomicrograph (a)diameter 50mm flyasp%,graphite 3% (b)diameter 37mm flyash 3% graphite 6% (c)50mm diameter flyash 6% graphite 3% (d diameter 37 mm flyasp% graphite 6% (e) diameter 25mm flyash 9% graphite 3% (f) diameter 25mm flyash 6% graphite 6%

2. CONCLUSIONS

MMCs containing up to 9% fly ash and graphite particles were easily fabricated. A uniform distribution of fly ash and graphite was observed in the matrix. The density of the composites decreases, whereas the hardness increases with increasing percentage of fly ash and graphite particulates.

The tensile strength and hardness strength increase with increasing percentage fly ash and graphite particulates. The MMC produced can be used for bearing applications, because of its good wear resistance.

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