Development and Evaluation of Tensile and Compression Strength of Al based MMC

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Development and Evaluation of Tensile and Compression Strength of Al based MMC

Kudithipati Narayanaswamy M.Tech student Mechanical Dept

Don Bosco Institute of Technology Bangalore, India

Shivanna

B S Praveen Kumar

Associate Professor, Mechanical Dept Don Bosco Institute of Technology

Bangalore, India

Associate Professor, Mechanical Dept Don Bosco Institute of Technology

Bangalore, India

AbstractThe Metal Matrix Composites have almost replaced the conventional metals due to their high strength, stiffness and durability. Aluminium based MMCs are most widely explored due to their low cost and availability. The present work focuses on the development and evaluation of tensile and compression properties of Al 7075 and fused SiO2 Metal matrix composite. Stir casting route has been adopted for the production of the composite. The specimens were subjected to T6 heat treatment. The reinforcement was varied in steps of 3%, 6%, 9% and 12%.

KeywordsAl 7075, Fused SiO2, Stir Casting, Heat Treatment (T6), Strength

  1. INTRODUCTION

    Metal matrix composites (MMCs) usually consist of a low- density metal, such as aluminum or magnesium, reinforced with particulate or fibers of a ceramic material, such as silicon carbide or graphite. Compared with unreinforced metals, MMCs offer higher specific strength and stiffness, higher operating temperature, and greater wear resistance, as well as the opportunity to tailor these properties for a particular application. New and high performance particle reinforced metal matrix composites (PRMMC) are expected to satisfy many requirements for a wide range of performance-driven, and price sensitive, applications in aerospace, automobiles, bicycles, golf clubs, and in other structural applications. In general, these materials exhibit higher strength and stiffness, in addition to isotropic behavior at a lower density, when compared to the un- reinforced matrix material. The recognition of the potential weight savings that can be achieved by using the advanced composites, which in turn means reduced cost and greater efficiency, was responsible for this growth in the technology of reinforcements, matrices and fabrication of composites. If the first two decades saw the improvements in the fabrication method, systematic study of properties and fracture mechanics was at the focal point in the 60s. Since then there has been an ever-increasing demand for new, strong, stiff and yet light-weight materials in fields such as aerospace, transportation and automobile and

    construction sectors. These materials have low specific gravity that makes their properties particularly superior in strength and modulus to many traditional engineering materials.

  2. SCOPE AND OBJECTIVE

    The aim of the present investigation is to develop and characterize tensile and compression properties of Al 7075 reinforced with fused SiO2. The objectives of the present work are as follows:

    • Preparations of composite by Stir Casting route.

    • Heat treatment (T6) of obtained composite specimens.

    • Preparation of specimens as per ASTM Standards.

    • Evaluation of tensile properties.

    • Evaluation of compression properties.

  3. EXPERIMENTAL SETUP

    A. selection of materials:

    Matrix Material

    Fig 1: Ingot Structure of Al 356

    Eleme nt

    Wt. %

    Element

    Wt. %

    Elemen t

    Wt. %

    Al

    87.1 – 91.4

    Mg

    2.1 – 2.9

    Si

    Max 0.4

    Cr

    0.18 – 0.28

    Mn

    Max 0.3

    Ti

    Max 0.2

    Cu

    1.2 – 2

    Other, each

    Max 0.05

    Zn

    5.1 – 6.1

    Fe

    Max 0.5

    Other, total

    Max 0.15

    Eleme nt

    Wt. %

    Element

    Wt. %

    Elemen t

    Wt. %

    Al

    87.1 – 91.4

    Mg

    2.1 – 2.9

    Si

    Max 0.4

    Cr

    0.18 – 0.28

    Mn

    Max 0.3

    Ti

    Max 0.2

    Cu

    1.2 – 2

    Other, each

    Max 0.05

    Zn

    5.1 – 6.1

    Fe

    Max 0.5

    Other, total

    Max 0.15

    Table 1: Chemical composition of Al 7075 Matrix Material

    Casting 4: Al 7075 + 9% Fused SiO2 (%)

    Casting 5: Al 7075 + 12% Fused SiO2 (%)

  4. EXPERIMENTAL DETAILS

    Reinforcement Material:

    A.Tensile test:

    Fig 3: Tensile Specimen

    Fig 2: Reinforcement Fused SiO2

    B.Fabrication by Stir Casting

    • Aluminum (Al 7075) 2kg was melted in the furnace to a temperature of 7500c

    • Addition of scum powder.

    • Formation of slag.

    • Slag removal.

    • After 10 mins degassing tablet 190 was added to remove the entrapped gases (degasification) and Stirrer was introduced.

    • Reinforcement material fused SiO2 powder was added according to the required proportions to molten metal in steps of 3% while stirring.

    • Stirrer was rotated at a speed of 0 to 300 rpm to create a vortex in the liquid metal.

    C. Percentage composition of matrix and reinforcement material:

    Table 2: Different wt% ratios of matrix metal & Reinforcement

    Samples

    Al 7075 (kg)

    Fused SiO2 (%)

    1

    2

    0

    2

    2

    3

    3

    2

    6

    4

    2

    9

    5

    2

    12

    The casting samples with different wt% reinforcements were

    Prepared respectively as shown below. Casting 1: Al 7075 + 0% Fused SiO2 (%)

    Casting 2: Al 7075 + 3% Fused SiO2 (%)

    Casting 3: Al 7075 + 6% Fused SiO2 (%)

    Properties that are directly measured via a tensile test are ultimate tensile strength, maximum elongation and reduction in area. The tests were conducted according to ASTM E8M – 04 at room temperatures

    Fig4: Specimens of Tensile test

    B.Compression test

    Compression test was carried out using a standard 10-ton capacity universal testing machine. Compression tests were conducted on specimens of 20 mm diameter and 3

    0 mm length machined from the cast compositesThe tests were conducted according to ASTM E9 at room temperature.

    Fig 5: Specimens of Tensile test

  5. RESULTS AND DISCUSSIONS:

    A. Tensile Test Results

    It is observed that the tensile strength and yield strength are increased at 3% weight of Fused SiO2 The increase in tensile strength is due to the presence of the hard and

    Strength (N/mm2)

    Strength (N/mm2)

    higher SiO2 particles embedded in the Al (7075) matrix, which act as a barrier to resist plastic flow when the composite is subjected to strain from an applied load. Also, the decreased interparticle spacing, due to the increasing weight percent f Fused SiO2 reinforcement, creates increased resistance to dislocation motion, which contributes to the enhanced strength of the composites.

    250

    200

    150

    100

    UTS

    YS

    250

    200

    150

    100

    UTS

    YS

    0 3 6 9 12

    Reinforcement in wt%

    0 3 6 9 12

    Reinforcement in wt%

    50

    0

    50

    0

    Fig 6: Variation of tensile strength and yield strength

    Compression strength (N/mm2)

    Compression strength (N/mm2)

    The resultant graph shows that the tensile properties are high in case of the composite Fused SiO2 as the reinforcement as compared to the aluminium alloy.

    1000

    900

    800

    700

    600

    500

    400

    300

    200

    100

    0

    1000

    900

    800

    700

    600

    500

    400

    300

    200

    100

    0

    0

    3

    6

    9

    12

    0

    3

    6

    9

    12

    Reinforcement in wt%

    Reinforcement in wt%

    Fig 7: Variation of compression strength

    The graph shows that the compression strength has increased with addition of reinforcement.

  6. CONCLUSION:

    From the experimental results it has been found that the tensile strength maximum at 3% reinforcement and there is marginal decrease in the tensile strength with increase percentage reinforcement. The compression strength has increased gradually and is maximum at 9% reinforcement.

  7. REFERENCES:

  1. K. Upadhya, composite materials for aerospace applications, developments in ceramics and metal matrix composites, Kamaleshwar Upadhya, Ed.., warren dale, PA: TMS publications, 1992, pp. 3-24.

  2. T.W. Clyne, An Introductory Overview of MMC System, Types and Developments, in Comprehensive Composite Materials, Vol-3; Metal Matrix Composites, T. W. Clyne (ed), Elsevier, 2000, pp.1- 26.

  3. L.M.Manocha & A.R. Bunsell Advances in composite materials, Pergamon Press, Oxford, 1980, Vol.2, p 1233- 1240.

  4. Ambient and elevated temperature mechanical properties of hot- pressed fused silica matrix composite D.C. Jia*, Y. Zhou, T.C. Lei, Journal of the European Ceramic Society, 28 April 2002.

  5. M.G. McKimpson and T.E.Scott, Processing and Properties of MMCs Containing Discontinuous Reinforcement, Mat. Sci. and Engg., Vol. 107A, 1989, pp 93-106.

  6. H.J. Rack, Metal Matrix Composites, Adv. Mater. Processes, Vol. 137 (1), 1990, pp 37-39.

  7. A. W. Urquhart, Molten Metals Sire MMCs, CMCs, Adv. . Mater. Processes, Vol. 140(7), 1991, pp 25-29.

  8. V. V. Bhanuprasad, K. S. Prasad, A.K. Kuruvilla, A. B. Pandey, B. V.

    R. Bhat and Y. R. Mahajan, Composite Strengthening in 6061 and Al-4Mg Alloys, . at. Sci. Vol. 26, 1991, pp 460-466.

  9. M. S. Zedias, P. S. Gilman and S.K.Das, High Temperature Discontinuously Reinforced Aluminium, JOM, Vol. 43(8), 1991, pp 29-31.

  10. JIWON PARK, S. SRIDHAR, and RICHARD J. FRUEHAN Ladle and Continuous Casting Process Models for Reduction of SiO2 in SiO2-Al2O3-CaO Slags by Al in Fe-Al(-Si) Melts The Minerals, Metals & Materials Society and ASM International 2014.

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