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A Review on Tribological And Mechanical Behaviors of Aluminium Metal Matrix Composites
1V. Hariharan, 2V.Mohankumar, 3P.Gnaneswaran
1Professor, 2PG Scholar, Department of Mechanical Engineering, Kongu Engineering College, Tamil Nadu, India
3Assistant Professor, Department of Mechanical Engineering, Park College of Engineering and Technology, Tamil Nadu, India.
Abstract-Aluminum hybrid metal matrix composites have been widely used as a substitute materials in automobile, aerospace and structural applications because of their good tribological and mechanical properties. The present study deals with aluminium alloy 7075 reinforced with ceramic particles and graphite particles. The addition of graphite content to aluminium alloy increase the wear resistance and also act as a solid lubricant material. The hardness, tensile strength, flexural strength and compression strength of the aluminium hybrid metal matrix composites are found to be increased by increasing the weight percentage of ceramic particles.
Keywords-Aluminium hybrid metal matrix composites;
Graphite; Ceramic particles; Wear.
I. INTRODUCTION
Aluminium is the most popular matrix material in the composites. Metal matrix composites (MMCs) reinforced with ceramic particles offer high strength, wear resistance, low density, good corrosion resistance, high thermal conductivity and low coefficient of thermal expansion and are promising materials for automotive, aircraft and aerospace applications. The most widely used reinforced particles in the aluminium matrix composites (AMCs) are ceramic particles and graphite particles. Aluminium matrix composites normally fabricated by liquid casting technique or powder metrology route [16, 17]. Using stir casting techniques improves wettability and excellent bonding between the ceramics and the metal [18, 19]. These methods are typically cost effective [20]. A number of researchers have been concentrated only in the 6xxx series aluminium matrix composites and only a few of them where focused in the 7xxx series hybrid composites. A detailed literature survey of aluminium hybrid metal matrix composites is made based on the following areas.
Tribological behaviour
Mechanical properties
II. TRIBOLOGICAL BEHAVIOUR
Researchers have been studies related to the tribological behaviours of aluminium metal matrix composites.
Baradeswaran and Elaya Perumal [1] have investigated
the 7075 aluminium alloy-graphite composites for its tribological behavior under dry sliding conditions. The wear rate of Al 7075 decreases with increasing graphite content and it was minimum about 5 wt. % of graphite which possesses the superior wear properties than that of other compositions 10, 15 and 20 wt. % of graphite.
Baradeswaran and Elaya Perumal [2] have investigated the effects of graphite and Al2O3 content in the Al 7075.
The Al 7075/Al2O3/graphite hybrid composite was prepared with 5 wt. % graphite particles addition and 2, 4, 6 and 8 wt. % of Al2O3 the wear rate decreases with the addition of Al2O3 and reaches a minimum at 2 wt. % Al2O3 and 5 wt. % of graphite and the wear rate is about 36% less than that of the matrix material Al 7075, whereas Fig. 1 and 2 shows the wear rate of the hybrid composites retains up to certain sliding speed and load.
The effect of graphite addition on friction coefficient is shown in Fig.3. The presence of graphite in the hybrid composite decreases the coefficient of friction.
Moreover the hybrid composites exhibited lower coefficient of expansion and wear rate. Ravinder Kumar and Suresh Dhiman [3] have investigated the specific wear rate of the unreinforced Al 7075 alloy and hybrid aluminium metal matrix composite reinforced with 7 wt.
% of SiC and 3 wt. % of graphite fabricated by using stir casting method. Finally the Specific wear rate of alloy and hybrid composite, decrease with increase in the sliding distance for low speed (2–4 m/s) and low load (20–40 N). However, at high speed and high load specific wear rate increases with increase of sliding distance.
Fig.1 Wear rate of hybrid composites (Baradeswaran et al. [1])
Fig.2 Wear rate of hybrid composites (Baradeswaran et al. [1])
Fig.3 Coefficient of friction of hybrid composites (Baradeswaran et al. [1])
Suresha and Sridhar [4] have investigated the dry sliding wear behaviour of Al matrix composites reinforced with Gr and SiC particulate up to 10%. Parametric studies indicate that the wear of hybrid composites has a tendency to increase beyond % reinforcement of 7.5%
and compare to the Al-Gr and Al-SiC composites, these hybrid composites exhibit better wear characteristics.
Uthayakumar et al. [5] have studied the dry sliding wear behaviour of aluminium reinforced with 5% SiC and 5%
B4C hybrid composite using a pin on disc tribometer.
The experimental results show that the hybrid composites retain the wear resistance properties up to 60 N load and sliding speed ranges 1–4 m/s. Bijay Kumar Show et al. [6] have investigated the dry sliding wear behaviour of 6351 Al alloy and its composites with single (Al2O3) and hybrid (Al2O3 + SiC) reinforcements at low sliding speed (1 m s-1) against a hardened EN 31 disk at different loads. At lower loads the Al 6351 hybrid composite exhibits lowest wear rate due to the presence of (SiC + Al2O3) particle that resist abrasive wear to a great extent. However, at higher loads the breakdown of (SiC+ Al2O3) particle clusters results in a high wear rate in the hybrid composite.
Devaraju Arjun et al. [7] have investigated the wear properties of aluminium alloy 6061-T6 reinforced with hybrid composites [(SiC + Gr) and (SiC + Al2O3)] using friction stir processing techniques. The micro-hardness will increases due to presence of pinning effect of hard particles in SiC and Al2O3. At the same time low wear
rate can be exhibit in SiC and Gr particles.
Baradeswaran et al. [8] has investigated the aluminium alloy (AA) 6061 and 7075 were reinforced with 10 wt.%
of boron carbide (B4C) and 5 wt.% of graphite through liquid casting technique. The high hardness and good % of elongation obtained in the AA 7075 hybrid composite compared to the AA 6061 alloy and its hybrid composite. Under this optimal condition, the AA 7075/B4C/graphite hybrid composite exhibits higher wear resistance property compared to base alloys and AA 6061 hybrid composite. Fig. 4, 5 and 6 shows that in the entire given applied load, sliding distance and sliding speed the Al 7075 hybrid composites has high wear resistance. Finally concluded that AA 7075 hybrid composite has good potential of tribological behaviour.
Veeresh kumar G.B et al. [9] reported that, wear resistance of the Al6061-SiC and Al7075-Al2O3 composites are higher but the SiC reinforcement contributed significantly in improving the wear resistance of Al6061-SiC composites, which exhibits superior mechanical and tribological properties. Vijaya Ramnath et al. [10] was studied the mechanical properties of aluminium alloy, alumina (Al2O3) and boron carbide metal matrix composites. Addition of Al2O3 and B4C in aluminium alloy improving the tensile strength, flexural strength and hardness.
Fig.4 Effect of applied load on wear rate (Baradeswaran et al. [8])
Fig.5 Effect of sliding distance on wear rate (Baradeswaran et al. [8])
Fig.6 Effect of sliding speed on wear rate (Baradeswaran et al. [8])
III. MECHANICAL PROPERTIES
Researchers have been studies related to the mechanical behaviours of aluminium hybrid metal matrix composites. Baradeswaran and Elaya Perumal [1]
studied that influence of the wear behaviour and mechanical properties of aluminium alloy 7075 reinforced with 0-8 wt. % of the Al2O3 and 5 wt. % of graphite particles. The ultimate tensile strength increases with increasing Al2O3 is shown in Fig.7 and it was noticed that the hybrid composites are greater than that of base alloy. It is known that the mechanical strength decreased due to the addition of graphite and for improving the mechanical strength, the Al2O3 hard ceramic particles are added.
Fig.7 Variation of tensile strength (Baradeswaran et al.
[1])
Fig.8 Variation of compression strength (Baradeswaran et al. [1])
Fig.9 Variation of flexural strength (Baradeswaran et al. [1])
Fig.10 Variations of hardness (Baradeswaran et al. [1]) Likewise the ultimate compressive strength of the hybrid composite was increased with the addition of Al2O3 is shown in Fig. 8 and it was improved 10% than that of base alloy. The flexural strength of the composites obtained from three point bending test is shown in Fig. 9 indicates that the flexural strength was increased with the addition of Al2O3 with graphite. Mohammad Tajally et al. [11] reported that a comparative analysis of the mechanical behaviour of cold-worked and annealed 7075 aluminium alloy. In above 265°C temperature, the rearrangement of the molecules inside the sample specimens at the same time yield and tensile strength gradually decreased. J.R. Gomes et al. [12] investigated that among many ceramic materials, SiC and Al2O3 are widely in use, due their favourable combination of density, hardness and cost effectiveness. When these reinforcements are combined with Al-MMCs, the resulting material exhibits significant increase in its elastic modulus, hardness, strength and wear resistance.
Reda et al. [13] have reported that pre-aging at various ret rogation temperatures improves the hardness, tensile properties and electrical resistivity of Al 7075. Doel and Bowen [14] have reported the improved tensile strength and lower ductility of Al 7075 reinforced with SiC particles than that of unreinforced. Zaklina Gnjidic et al.
[15] investigated that, the SiC particles increases the yield strength and elastic modulus, but decreases the
ultimate compressive strength and ductility of the Al7XXX base alloy.
IV. CONCLUSION
The present literature study for AA 7075 hybrid metal matrix reinforced with ceramic and graphite particles.
The addition of graphite content to aluminium alloy increase the wear resistance up to certain wt. % of graphite particles and decrease the hardness of composites. Also the machinability is increased with addition of graphite particles. The effect of adding ceramic particles such as SiC, Al2O3 and B4C in AA 7075 to increase the mechanical properties such as tensile strength, compressive strength and flexural strength.
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