STUDIES OF MECHANICAL PROPERTIES ON ALUMINIUM HYBRID METAL MATRIX COMPOSITE

Transcription

1 Abstract International Journal of Emerging Researches in Engineering Science and Technology, Volume 2, Issue 6, July 15 STUDIES OF MECHANICAL PROPERTIES ON ALUMINIUM HYBRID METAL MATRIX COMPOSITE B.Sundar 1, B.Rajeswari 2, K.S.Amirthagadeswaran 3 Department of Mechanical Engineering, Government College of Technology, Coimbatore , India 1 bsundarbose@gmail.com Recently aluminium based metal matrix composite is emerging as a promising material for structural, aerospace, marine and automobile applications. In the present study Aluminium 7075 alloy reinforced with silicon carbide (SiC) and alumina (Al 2O 3) particulates to form aluminium metal matrix hybrid composite using stir casting technique. This technique is less expensive and very effective. The mechanical properties (Hardness, Tensile strength and Fracture toughness) of stir cast hybrid aluminium composites reinforced with various weight fractions of SiC and Al 2O 3 particulates of 2.5%, 5% and 7.5% reinforcement were tested and compared with various compositions of Al-SiC-Al2O3 composites. The results revealed that the addition of silicon carbide and alumina particles in aluminium matrix improving the mechanical properties. Keywords: Metal matrix composite, Silicon carbide, Alumina, Stir casting,mechanical properties. I. INTRODUCTION A typical composite material is a system of materials composing of two or more materials (mixed and bonded) on a macroscopic scale. Generally, a composite material is composed of reinforcement (fibers, particles, flakes and fillers) embedded in a matrix (polymers, metals, or ceramics). The matrix holds the reinforcement to form the desired shape while the reinforcement improves the overall mechanical properties of the matrix. When designed properly the new combined material exhibits better strength than would each individual material. Particle reinforced aluminium matrix composite possesses the significantly enhanced properties including high strength, high stiffness and damping capacity compared with the unreinforced alloy matrix [3].SiC particle reinforced aluminium composites have received more commercial attention than other kinds of MMCs due to their high performance, high mechanical properties, wear resistance, low coefficient of thermal expansion and high thermal conductivity. Therefore they are more competitive on MMC market and find wider application in industries [1]. Aluminium 7075 alloy matrix composites with combined reinforcement of SiC and Al 2O 3 have exhibited improved mechanical properties compared to the composites reinforced with either SiC or Al 2O 3 alone. Hardness of the composite increase because of increase in ceramic phase due to the addition of SiC particulates [2]. Oxidation resistance of matrix material was significantly improved using SiC particulate with a minimal addition of Al 2O 3 [4]. The composite has been fabricated without applying stirring process, particle clustering occurred in some places and some places were identified without SiC inclusion. Wettability between most ceramic particles and liquid metals has been poor so mechanical force was given to overcome surface tension to improve wettability. To improve the particle distribution heat the molten matrix alloy to a temperature above the liquidus and then stir the melts using an automatic device for 10 minutes at 600 rpm [6]. There are numerous methods for fabricating composite components. Composite fabrication usually involves wetting, 77

2 mixing or saturating the reinforcement with the matrix, and then causing the matrix to bind together (with heat or a chemical reaction) into a rigid structure. Selection of a method will depend on the materials, the part design and end-use or application. Fabrication of composite materials is accomplished by a wide variety of techniques such as powder metallurgy, squeeze casting, spray deposition and stir casting. The conventional stir casting is an attractive processing method for producing AMCs as it is relatively inexpensive and offers a wide selection of materials and processing conditions and suitable for mass production and production of complex profiled composite components without damaging the reinforcement particles. Cost was the major thing for the producing components of even minimally complex shapes. Casting technology is the key thing to overcome this problem. In order to achieve high mechanical properties, it is essential to achieve the uniform distribution of reinforcement within the matrix. The porosity is another common problem exists in the MMC [7]. The composite gives longer fatigue life than unreinforced alloy in lower stress state. The fatigue behavior of AMCs is a very important factor in engineering applications involving cyclic or dynamic loading. It has been reported that incorporation of hard ceramic particles resulted in low crack propagation rates, especially at low stress intensity factor levels in composite materials compared with their unreinforced counterpart [13]. The stirrer geometry has significant effects on the flow pattern in the stirred crucible. When the geometry is ranged from the single stage to the multistage the volume fraction of stagnant zone in cylinder part decreases [3]. Stir casting method is used to fabricate the hybrid metal matrix composite. A weighted quantity of the aluminium 7075 alloy was heated in vacuum metal melting furnace. The melt was superheated by about 100 o C to get the fluidity. And weighted quantity of reinforcement particles (SiC and Al 2O 3) are pre heated at 900 o C in pre heating furnace. After pre heating the reinforcement particles are added to the matrix material (matrix material in liquid state). During the process, the molten metal was well agitated by a multistage stirrer to create turbulence motion. The multistage stirrer is helpful to eliminate the undesirable zone in the crucible compared with the single stage stirrer. The stir was rotate at 600 rpm. Then the molten mixer was pour into the die, which is preheated to about 300 o C. The stir casting method used to prepare the composites could produce uniform distribution of the reinforced fly ash particles. The Tensile Strength, Compression Strength and Hardness increased with the increase in the weight fraction of reinforced fly ash and decreased with increase in particle size of the fly ash. The ductility of the composite decreased with increase in the weight fraction of reinforced fly ash and decreased with increase in particle size of the fly ash [14]. II. EXPERIMENTAL DETAILS Aluminium 7075 alloy has been used for the work aluminum alloy's composition roughly includes % zinc, % magnesium, % copper and less than half a percent of silicon, iron, manganese, titanium, chromium. The uniform hardness values were achieved at 600 rpm with 10 min stirring [1]. 78

3 Fig 1 Stir casting set up and multi stirrer blade A.Hardness test result III. RESULT AND DISCUSSION In this test a 5 mm indentation ball is used to apply load. 500 kg load is applied on the work piece without any jerk for 10 to 15 seconds. By using microscope we measure the indentation diameter and by using formula we measure the hardness value. TABLE I HARDNESS TEST RESULT load is applied. By using the fractured specimen we measure the strain value of the composition. TABLE 2 TENSILE STRENGTH RESULT S.No %Composition Of Reinforcement Ultimate Tensile Strength (Mpa) 1 7.5% Al 2O %SiC + 5% Al 2O %SiC + 2.5% Al 2O S.NO %Composition of Hardness (BHN) Reinforcement 1 7.5% Al 2O %SiC + 5% Al 2O %SiC + 2.5% Al 2O Fig 3 Tensile tested specimen C) Fracture toughness test result B) Tensile test result Fig 2 Hardness tested specimen The specimen to be tested is fastened to the two end jaws of the UTM machine. Now load is applied gradually on the specimen by means of the movable crosshead, till the specimen features. During the test, the magnitude of load is measured by the load measuring unit. A strain gauge is used to measure the elongation of the specimen between the gauge marks when the The Izod impact test is a dynamic test in which a test piece V-notched test piece, gripped vertically, is broken by a single blow of a freely swinging pendulum. The blow is struck on the same face as the notch and at the fixed height above it. The energy absorbed is measured. This absorbed energy is a measure of the fracture toughness of material. S.NO TABLE 3 FRACTURE TOUGHNESS RESULT %Composition of Reinforcement Fracture Toughness (MPa-m 1/2 ) 1 7.5% Al 2O

4 2 5%SiC + 5% Al 2O %SiC + 2.5% Al 2O % Al2O3 Hardness (BHN) 5%SiC + 5% Al2O3 7.5%SiC + 2.5% Al2O3 Hardness (BHN) Ultimate tensile strength (MPa) Fracture Toughness (MPa-m1/2) % Al2O3 5%SiC + 5% Al2O3 7.5%SiC + 2.5% Al2O3 Ultimate 19 tensile strength 18.5 (MPa) % Al2O3 5%SiC + 7.5%SiC + 5% Al2O3 2.5% Al2O3 Fracture Toughness (MPa-m1/2) Fig 4 shows the effect of reinforcement in aluminium matrix alloy From the table 1 the hardness value of the composite material increases and from the table 2 the tensile strength of the composite also increase gradually but the fracture toughness of the composite get degrease because of the ceramic reinforcement particles. From the above tables the hardness and tensile strength of the composite material get increased and fracture toughness value get reduced, IV. CONCLUSION The influence of percentage of reinforcement on mechanical properties of Al7075-SiC-Al2O3 hybrid metal matrix composite was found out. The mechanical properties of the composite were tested and compared with various compositions of Al-SiC-Al2O3 composites. Aluminium 7075 with 7.5% silicon carbide and 2.5% alumina has a maximum hardness, ultimate tensile value. Fracture toughness decreases with increase in SiC particulate, because of the ceramic property of silicon carbide. By adding more than 20% of reinforcement to aluminium matrix alloy, the mechanical property of matrix alloy comes below the normal value because of uneven mixer of reinforcement. The results revealed that the addition of silicon carbide and alumina particles in aluminium matrix improving the mechanical properties of the matrix alloy. V. REFERENCES [1] S. BalasivanandhaPrabu, L. Karunamoorthy, S. Kathiresan and B. Mohan., Influence of stirring speed and stirring time on distribution of particles in cast 80

5 metal matrix composite Journal of Materials Processing Technology 171 (2006) [2] S.Suresha, B.K. Sridhara., Friction characteristics of aluminum silicon carbide graphite hybrid composites, Materials and Design 34 (2012) [3] Hai Su,WenliGao, Hui Zhang,Hongbo Liu, Jian Lu and Zheng Lu., Optimization of Stirring Parameters Through Numerical Simulation for the Preparation of Aluminum Matrix Composite by Stir Casting Process, Journal of Manufacturing Science and Engineering 132 (2010). [4] Keiichiro Suzuki, Nobuo Kageyama and Takashi Kanno., Improvement in the oxidation resistance of liquid-phase-sintered silicon carbide with aluminum oxide additions, Ceramics International 31 (2005) [5] S. Suresha and B.K. Sridhara., Effect of addition of graphite particulates on the wear behaviour in aluminium silicon carbide graphite composites Materials and Design 31 (2010) [6] ManojSingla, D. Deepak Dwivedi, Lakhvir Singh and VikasChawla., Development of Aluminium Based Silicon Carbide Particulate Metal Matrix Composite Journal of Minerals & Materials Characterization & Engineering, 8(2009) [7] J. Hashim, L. Looney, M.S.J. Hashmi, Particle distribution in cast metal matrix composites, Part 1, J. Mater.Process. Technol. 123 (2002) [8] Giovanni Belingardi and Roberto Vadori., Low velocity impact tests of laminate glass-fiber-epoxy matrix composite material plates, International Journal of Impact Engineering 27 (2002) [9] K.M. Shorowordi, T. Laoui, A.S.M.A. Haseeb, J.P. Celis and L. Froyen., Microstructure and interface characteristics of B4C, SiC and Al2O3 reinforced Al matrix composites: a comparative study, Journal of Materials Processing Technology 142 (2003) [10] Kwang-Young Lima, Young-Wook Kim, Toshiyuki Nishimura and Won- SeonSeo., High temperature strength of silicon carbide sintered with 1 wt. % aluminium nitride and lutetium oxide, Journal of the European Ceramic Society 33 (2013) [11] Keiichiro Suzuki, Nobuo Kageyama and Takashi Kanno., Improvement in the oxidation resistance of liquid-phase-sintered silicon carbide with aluminum oxide additions, Ceramics International 31 (2005) [12] G. Abouelmagd., Hot deformation and wear resistance of P/M aluminium metal matrix composites, Journal of Materials Processing Technology (2004) [13] S. Arivukkarasan, V. Dhanalakshmi, A. Suresh babu and M. Aruna.,Performance Study on Fatigue Behaviour in Aluminium Alloy and Alumina Silicate Particulate Composites Journal of Applied Science and Engineering, 16 (2013) [14] H.C. Anilkumar, H.S. Hebbar and K.S. Ravishankar., mechanical properties of fly ash reinforced aluminium alloy (al6061) composites,international Journal of Mechanical and Materials Engineering. 6 (2011)