Synthesis and Characterization of Al1100-Cu Alloy Reinforced with Al2

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International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)

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ISSN (Print): 2319-3182, Volume -5, Issue-1, 2016 40

Synthesis and Characterization of Al1100-Cu Alloy Reinforced with Al

₂

o

₃

Particulate Metal Matrix Composites

1Hemanth kumar.V, ²Siddalingeshwara.M.N, ³Chethana.V, ⁴Dudhat Akshay.D,⁵Srinuvasu.N

1,2,3,4,5

Dept. of Mechanical Engineering, R.R. Institute of Technology, Bangalore, India.

Abstract— Aluminium1100-Cu Alloy-Reinforced with Al2O3 particulate composites possess a unique combination of high specific strength, high wear resistance.

Aluminium metal matrix composites (MMCs) have attracted considerable interest in various industries due to their inherent good mechanical properties and low cost.

Aluminium MMCs are preferred to other conventional materials in the fields of aerospace, automotive and marine applications owing to their improved properties like high strength to weight ratio. The composites are prepared using the liquid metallurgy technique (stir casting technique), in which Al2O3 particulates were dispersed in the base matrix in steps of 3 into the Al-Cu Alloys. The amount of reinforcement is varied from 0 to 4 wt %. The prepared composites are subjected to the mechanical testing as per the ASTM standards. The Mechanical properties like tensile strength and hardness (Vickers Hardness) test are tested in laboratory and results are tabulated. The tabulated experimental results of Al1100- Cu- Al2O3 composites are evaluated.

Index Terms— Aluminium, hardness matrix, reinforcement, tensile strength

I. INTRODUCTION

Many of our modern technologies require materials with unusual combinations of properties that cannot be met by the conventional metal alloys, ceramics, and polymeric materials. This is especially true for materials that are needed for aerospace, underwater, and transportation applications. For example, aircraft engineers are increasingly searching for structural materials that have low densities, are strong, stiff, and abrasion and impact resistant, and are not easily corroded[1]. This is a rather formidable combination of characteristics. Frequently, strong materials are relatively dense; also, increasing the strength or stiffness generally results in impact strength.

Material property combinations and ranges have been, and are yet being, extended by the development of composite materials. Generally speaking, a composite is considered to be any multiphase material that exhibits a significant proportion of the properties of both constituent phases that a better combination of properties is realized. According to this principle of combined action, better property combinations are

fashioned by the judicious combination of two or more distinct materials. Property trade-offs are also made for many composites.

Composites of sorts include multiphase metal alloys, ceramics, and polymers. For example, pearlitic steels have a microstructure consisting layers of ferrite and cementite. The ferrite phase is soft and ductile, whereas cementite is hard and very brittle. The combined mechanical characteristics of the peralite are superior to those of either of the constituent phases. There are also a number of composites that occur in nature. For example, wood consists of strong and flexible cellulose fibers surrounded and held together by a stiffer material called lignin. Also, bone is composite of the strong yet soft protein collagen and the hard, brittle mineral apatite. A composite, in the present context, is a multiphase material that is artificially made, as opposed to one that occurs or forms naturally. In addition, the constituent phases must be chemically dissimilar and many ceramics do not fit this definition because their multiple phases are formed as a consequence of natural phenomena.

In designing composite materials, scientists and engineers have ingeniously combined various metals, ceramics, and polymers produce a new generation of extraordinary materials. Most composites have been created to improve combinations of mechanical characteristics such as stiffness, toughness, and ambient and high temperature strength.

Composite materials are engineering materials made from two or more constituent materials that remain separate and distinct on a macroscopic level while forming a single component. There are two categories o constituent materials: matrix and reinforcement. The matrix material surrounds and supports the reinforcement materials by maintaining their relative positions. The reinforcements impart their special mechanical and physical properties to enhance the matrix properties[2]. A synergism produces material properties unavailable from the individual constituent materials. Due to the wide variety of matrix and reinforcement materials available, the design potentials are incredible

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II. EXPERIMENTAL SETUP

A. Materials used

In the present work we chosen AL1100-CU is matrix material and AL2O3 is reinforcement.

Table 1: shows the properties of matrix and reinforcing materials used in the study [3]

Properties Al1100 AL₂O₃

Melting point 650°c 2072°c

Density (g/cc) 2.7 3.69

Poisson’s ratio 0.33 0.21

Strength (Tensile/ Compressive) Mpa

115 (T) 2100 (C)

Hardness (HB500) 30 1175

Elastic modulus (GPa) 70-80 300 B. Preparation of AL1100 +AL2O3 composite by stir casting

Among the variety of manufacturing processes available for particulate reinforced metal matrix composites, the stir casting technique is the simplest and the most economical process for producing particulate reinforced MMCs. In this method, in order to achieve the optimum properties of the metal matrix composite, the distribution of the reinforcement material in the matrix should be uniform and the wettability between the molten matrix and reinforcement particles should be optimized. The porosity level with cast metal matrix composite should be minimized and the chemical reaction between the reinforcement material and the matrix must be avoided. The vortex method is one of the better known approaches used to create a good distribution of the reinforcement material in the matrix.

In this, after the matrix material is melted, it is stirred vigorously by a mechanical stirrer to form a vortex at the surface of the melt and the reinforcement material is then introduced at the side of the vortex. Good quality composites can be produced by this method by proper selection of the process parameters such as pouring temperature, stirring speed, preheating temperature of reinforcement etc. Preparation of the hybrid composite was carried out according to the following procedure:

About 1kg of Al1100 alloy was melted in a graphite crucible in an induction type electric resistance furnace.

The temperature of the melt was 725ºC.After complete melting and degassing of the alloy by nitrogen, a simple mechanical four-blade alumina coated stainless steel stirrer was introduced into the melt and stirring was started. The coating of an alumina to the blades of the stirrer is essential to prevent the migration of ferrous ions from the stirrer into the molten metal. The stirrer was rotated a 600 rpm for 20min. The depth of immersion of the stirrer was maintained at about two thirds the depth of the molten metal.

During stirring, the mixture of preheated reinforcement particles SiC and Gr in equal volume fraction was added inside the vortex formed due to stirring. The reinforcement particles were preheated to 600ºC for an hour before addition. Their average diameters were 75 µm respectively. After complete addition of the particles to the melt, the composite alloy was tilt poured into the preheated (250 ºC) permanent steel mould and allowed to cool in atmospheric air. The billet was then removed from the mould. The Al1100 hybrid composites of different volume fractions(0%,2%,4% of reinforcement materials were thus produced and wear specimens were machined from them. A sectional view of the stir casting is shown in fig 1.0

Fig 1.0 Stir Casting

III. TESTING

A. Tensile test

The monotonic static tension test is the most common testing methodology for determining mechanical properties of metals. In general, tension tests provide information related to the strength and ductility of metals under direct tension stress. It is a very common testing procedure for quality control and specification validation. One should be very careful to recognize that a static tension test may not reflect the actual in service behavior of the material. For example, the tension test is conducted with controlled loading rates, high-tolerance machining of specimens, controlled temperature conditions, and other environmental conditions unique to the laboratory. However, the data obtained from tension testing is very useful for design purposes i. Test specimen preparation

Testing specimen was prepared according to the American Standard Testing Materials (ASTM) [4] as shown in figure.2

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Fig 2: tensile test specimen

Fig 3: Photographs of Tensile Test Specimens (Al-1100 with different compositions of alumina) ii. Equations

Deformation = P X L/A X E Stress = Force/ area

%age of elongation = L_f –L_{i / L}i

By these above formulae the tensile strength of the composite material can be found.

Fig 4: Electronic Universal Testing Machine

B. Vickers hardness test

The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. The Vickers test is often easier to use than other hardness tests since the required calculations are independent of the size of the indenter, and the indenter can be used for all materials irrespective of hardness. The basic principle, as with all common measures of hardness, is to observe the questioned material's ability to resist plastic deformation from a standard source. The Vickers test can be used for all metals and has one of the widest scales among hardness tests. The unit of hardness given by the test is known as the Vickers Pyramid Number (HV) or Diamond Pyramid Hardness (DPH). The hardness number can be converted into units of pascals, but should not be confused with a pressure, which also has units of pascals. The hardness number is determined by the load over the surface area of the indentation and not the area normal to the force, and is therefore not a pressure.

i. Test equipment

Vickers hardness testing machine is shown in the fig below. It consists of a microscope, a diamond indenter, a light source and is connected to a computer. Different positions of the specimen can be accessed by moving the platform of the microscope.

Fig 5 :Vickers test equipment

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IV. RESULTS

A. Tensile test

Table 2: tabular list for tensile test values SI Material tensile strength

(N/mm2)

% of Elongation 1 AL1100 with 0%

of Al2O3

140.6 14.3

2 AL1100 with 2%

of Al2O3

165.2 11.8

3 AL1100 with 2%

of Al2O3

174.5 10.62

These are results obtained of tensile test for different trails of different composition of alumina into the al1100 cu alloy

It can be observed from the above tensile test results that the tensile strength has increased with increase in the percentage of Al₂O₃. This indicates that the specimen with higher percentage of the reinforcement can withstand a larger amount of load before fracture. The percentage elongation of the specimen decreases with increase in the percentage of Al₂O₃. This is a good attribute because it indicates that the dimensional stability is high for the specimen with higher percentage of the reinforcement.

Graph 1: tensile strength variation graph B. Vickers Hardness Test

Graph 2: VHN variations with different compositions

From the above graph 2 it can clearly be seen that the Vickers Hardness Number has increased with increase in the percentage of Al₂O₃. This indicates that the hardness of the composite has increased with the addition of Al₂O₃.

V. CONCLUSION

The results of the present investigation may be summarized as follows: The composite Al1100/Al₂O₃ was successfully produced by liquid metallurgy route.

The manufactured Al1100-Al₂O₃ composites exhibited higher values of tensile Strength than the base alloy Al1100.It was revealed that the hardness of composite samples increased with increasing the weight percentage of Al₂O₃ particles. The ductility of the composite was found to be slightly lower than that of the aluminum 1100alloy.

REFERENCES

[1] Szu Ying Yu, Hitoshi Ishii, Keiichiro Tohgo, Young Tae Cho, DongfengDiao, “Temperature dependence of sliding wearbehavior in SiC whisker or SiC particulate reinforced 6061 aluminumalloy composite”, Wear 213 (1997) 21- 28.

[2] H.C. How, T.N. Baker, “Dry sliding wear behaviour of Saffil-reinforced AA6061 composites”, Wear 210 (1997) 263-272.

[3] J. Gilbert Kaufman “Properties of AluminumAlloys; Tensile, Creep, and Fatigue Data at High and Low Temperatures”, ASM International2002.

[4] ASM handbook of Composites, Volume 21.54 G.

B. Veeresh Kumar, C. S. P. Rao, N. Selvaraj, M.

S. Bhagyashekar Vol.9, No.1

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