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1. By Rakesh Kumar (2023RSME024) Study of Mechanical And Tribological properties of Metal matrix composite(MMCs)

2. Contents

3. Conventional Engineering materials have limitations in achieving good combination of strength, stiffness, toughness and density. To overcome these shortcomings and to meet the ever increasing demand of modern day technology, composites are most favorable materials of recent interest. MMCs are being developed to fulfill various performance requirements. MMCs are stronger and lightweight; so used as structural materials in aircraft, helicopters, spacecrafts, automobile etc. Introduction

4. What is composite A materials system composed of two or more physically distinct phases whose combination produces aggregate properties that are different from those of its constituents. OR, Composite material consists of two or more materials that differ in chemical and physical properties and are not soluble in one another. Composite = Matrix + Fiber (Reinforcement) The matrix and reinforcement materials can either be organic (polymer), inorganic (glass, ceramic) or metallic (aluminum, titanium etc ). When at least three materials are present, it is called a hybrid -composite.

5. There are two classification systems of composite materials. One of them is based on the matrix material (metal, ceramic, polymer) and the second is based on the reinforcing material structure: (Based on matrix material) Metal Matrix Composites (MMC) Ceramic Matrix Composites (CMC) Polymer Matrix Composites (PMC) (Based on reinforcing material structure) Particulate Composites Fibrous Composites Laminate Composites Classification Of Composites

6. Metal matrix composites are High strength, fracture toughness and stiffness are offered by metal matrices They can withstand elevated temperature in corrosive environment MMCs are widely used in engineering applications where the operating temperature lies in between 250 °C to 750 °C. METAL MATRIX COMPOSITES (MMCS)

7. Stir Casting: Matrix and Reinforcement

8. The matrix is the monolithic material into which the reinforcement is embedded and is completely continuous. In structural application, the matrix is usually a lighter metal such as Aluminum, magnesium or, titanium and provide a compliant support for reinforcement . In high temperature application cobalt and cobalt nickel alloy matrices are common. Function of Matrix Binds fibre Act as medium Protect fibre Prevent propagation of cracks. Different Matrix for MMCs Aluminum matrix composite Magnesium Matrix composite Copper Matrix composite Titanium Matrix composite Matrices for MMCs

9. Matrix material Salient properties Applications Al Pure/AA1100 (Al99) Recyclability, ductility, workability and corrosion resistance Metal spinning, decorated foil pouches for food and drink, food packaging trays AA2024 (AlCu4Mg1)   High strength to weight ratio, machining to a high surface finish, high fatigue strength, high specific strength   Thin sheets, truck wheels, aircraft structures, screw machine products, scientific instruments, veterinary and orthopaedic braces, and rivets AA6061 (AlMg1SiCu) Excellent for heat treatment, easy to work, weld and machine the product with reasonable strength   For all kind of structural applications especially a truck, marine frames, railroad cars, and pipelines AA7075 (Al-Zn6MgCu) High fatigue strength, high corrosion resistance, reasonable machinability, high strength-to-density ratio   Rock climbing equipment, bicycle components, in line skating-frames and hang glider airframes A413/LM6 (AlMg6) Excellent fluidity property, high strength, good workability, and high resistance to corrosion Military and aerospace application due to its excellent joining characteristics A356/LM25 (Al-Si7Mg) Excellent castability, machinability, wear resistance and lightweight Refractory in the thermal protection system, engine piston, moving parts in automobiles Frequently used Al matrix materials for the production of AMMCs.

10. The following demand are generally applicable Low density Mechanical Compatibility Thermal stability High Young’s Modulus Good process ability Economic efficiency The reinforcement material is embedded into the matrix. Reinforcement is used to enhance mechanical & tribological properties. It is used to change physical properties such as wear resistance, friction coefficient, or thermal conductivity. The reinforcement can be either continuous, or discontinuous. Reinforcing materials in MMC are silicon carbide, boron carbide, alumina, and graphite. In the form of particles, short fibers (whiskers) or long fibers. Reinforcement for MMCS

11. Percentage of Reinforcement used in mmcs

12. Properties Of Various Particulate Reinforcements Used In The Production Of MMCs Reinforcement properties Application Al 2 O 3 High strength to weight ratio, High hardness   Brake discs, pistons, cylinder heads, connecting rods SiC High hardness, stiffness, specific strength, and thermal properties. Resistant to acids, alkalis Pistons, brake rotors, callipers, liners, propeller shaft, connecting rod, brake rotors, driveshaft, engine cradle, brake disc on ICE bogies   B 4 C High strength, low density, high hardness, excellent chemical stability, and neutron absorption capability   Automotive applications TiO 2 Strong bonding, high tensile strength, hardness and impact strength Automobile applications SiO 2 Superior mechanical and tribological properties Wear-resistant applications ZrO 2 High hardness and wear resistance Pistons, cylinder liners, and connecting rods TiN High strength and wear resistance Cutting tools, solar-control films, and other microelectronic applications. Excellent diffusion barrier against most of the metals   CNT High strength-to-weight ratio, low density, increase in yield strength, tensile strength, ductility, and hardness   Brake shoes, cylinder liners and aircraft landing gears Si 3 N 4 High hardness and tensile strength Automotive parts Fly ash   Lower cost, high tensile strength, compressive strength, impact strength, and hardness   Covers, pans, shrouds, casings, pulleys, manifolds, valve covers, brake rotors, and engine blocks in automobiles TiC High wear resistance Pistons, connecting rods ZrB2 High exothermic formation, thermodynamic stability, better bonding strength, high hardness, and wear resistance   Aerospace applications BN High strength, low density, high hardness -------------- TiB2 High strength and wear resistance High-tech structural and functional applications including aerospace, defence, automotive, and thermal management areas, as well as in sports Red mud   Low cost, tensile strength, compression strength, and hardness increased with the increase in the weight fraction  Aircraft industry, marine components, bicycle industry, drive shafts, electrical parts and equipment’s, brakes, fittings WS2 Self-lubrication, improved friction and wear properties. Moving parts of engines

13. Fig: Framework for producing better quality AMMCs by a stir casting process

14. Challenges In the Production of Metal matrix composite The main technical challenges can be listed as: reinforcement selection; dispersion of reinforcement within the matrix reactivity between the reinforcement and matrix interfacial bonding preferred orientation of reinforcement .

15. Objectives To develop the MMCs which are having high fatigue strength, good wear- resistant, light in weight useful for fabrication of Automobile components. The most important objective is to fabricate metal- matrix composite, which are having tendency to withstand high temperature working condition. To test the hardness/wear resistance and the impact strength of the metal-matrix composite. 15

16. FABRICATION TECHNIQUES OF AMMC

17. Stir Casting Technique for MMCs Stir casting is the simplest and the most economical method for the fabrication of aluminum metal matrix composite. In this method a molten aluminum metal is melted at a definite temperature in a furnace and then a preheated reinforcement particulates are mixed with molten alloy & then stirrer is used to mix the molten metal with reinforcement particles.     Stir casting is a process of mixing dispersed phase ceramic particles or short fibres in a molten matrix metal using mechanical stirring .

18. Wettability Figure 1 Schematic illustration of contact angle in a (a) non-wetting system, and (b) wetting system. It is defined as extent where a liquid will spread over a solid surface Good wettability means liquid matrix flows over reinforcement The wettability of a solid by a liquid is indicated by the contact angle, as shown in Fig. 1. The contact angle, h, between solid, liquid and gas/vapour is related by the Young— Dupre’s equation,

19. Thermal processing and the (a) effect of different temperature and (b) time of treatments were briefly discussed based on the current literature. Mechanical treatments (wherein the stir casting by mechanical impellers as well as acoustic-based processes are presented); the effect of impeller design and configurations are introduced and that the main influencing aspects of ultrasonic melt treatment are explained. Other methods based on reactive wettings are compactly mentioned (wherein an alloying agent ( e.G. , Mg) addition to al composite melt , is added to a composite slurry to enhance the affi nity in interfacial region of reinforcer and matrix . Reinforcing agent is coated by a metal or ceramic ( to prevent melt attack to the strengthening particles ) Wettability improvement Method Wettability can be improved by some of the important techniques Surface treatments and coating of the reinforcement.

20. Interface has a strong influence over the properties of the metal matrix composites. Strengthening in the composites by the reinforcements is dependent on the interfacial bond strength between the matrix and the reinforcement. Interfacial bonding permits transfer and distribution of the load from the matrix to the reinforcement. A mechanical bonding arises from mechanical interlocking between the matrix and reinforcements in the absence of all chemical sources of bonding and it is significant only in the case of fibre-reinforced composite. Chemical bonding occurs when the atoms of matrix and reinforcement are in direct contact and is accomplished by exchange of electrons. Why are Reinforcement-matrix interfaces important? Fig : 2 Interfaces between phases in a composite material: Direct - bonding between primary and secondary phases

21. Literature Review TITLE AUTHORS WORK FINDINGS Investigation of Mechanical Properties of Aluminium Based Metal Matrix Composites Reinforced with Sic & Al2O3. Haider et al.2015 fabrication of aluminium 6061 based metal matrix composites, Reinforced with silicon carbide and Al2O3 by stir casting technique. The percentage of one reinforcement particulate is kept constant and varying other and vice versa, namely type I and type II composites > Hardness of the SiC & Al2O3 filled Al6061 alloy composites found increased with increased ceramic particulates content. > Finer the grain size better is the hardness and strength of composites leading to lowering of wear rates.  Analysing the mechanical properties of aluminium ( SiC , B4C) hybrid Composite. Kannan et al 2021 > Al 7475 is a base metal and reinforced with SiC, B4C in different combinations of composition like 85%Al 7.5%SiC 7.5%B4C, 85%Al 5%SiC 10%B4C, 85%Al 10%SiC 5%B4C by stir casting method. > Stir casted composite is machined carefully to prepare specimen for different mechanical property test > With the addition of SiC increases the hardness is increases and tensile test value is decreases. > With the addition of B4C increases the tensile test value is increases and hardness test value is decreases.   Experimental Analysis of Mechanical Properties on Hybrid metal Matrix Composite (AA7175/ B4C/SiC/graphite) Kumar et al.2023 > In this research, AA7175 has been used with SiC, B4C & Graphite as reinforcements in different amounts (3, 6, 9, 12 respectively) of weight percent. > Mechanical properties of HAMCs i.e., hardness, tensile strength & percentage elongation have been analysed. > Hybrid Composite is continuously stirred for homogenous mixing of reinforcements in aluminium alloy >During the experiments, it has been analysed that the rate of hardness increases with the increment of weight percentage of reinforcements and the maximum hardness is found at 12% wt reinforcements.

22. TITLE AUTHORS WORK FINDINGS Wettability enhancement of aluminum metal matrix composite reinforced with magnesium coated silicon carbide particles E M Gutema, V Yu Bazhin and S N Fedorov (2018) The adhesion at the interface between the matrix and reinforcement plays a major role in determining mechanical properties of Aluminum Metal Matrix Composite (AMMCs). Various techniques are developed for better properties incorporation of magnesium as coating material for SiC enhances the wettability between the matrix and reinforcement. The addition of magnesium as reinforcement along with SiC increases the tensile strength from 82 MPa to 135 MPa. An optimum content of SiC and Mg at which the composites exhibited good tensile strength is found to be Al+12%SiC+2Mg ratio. The hardness of the composite with the incorporation of Mg is higher than that of composite reinforced only by different weight fraction of SiC. The Brinell hardness of the composite raised enhanced. Mechanical & Tribological Behavior of Stir Cast LM6 – Fly ash Composite A k Dhar Aand G Sutradhar (2021) in order to enhance characteristics while minimizing the cost of production. Fly ash (2%, 5%, and 8% by weight) was used to make Al alloy MMC through stir casting method Tribological test is performed on block on roller tribotester to ascertain the wear and Cof properties of composites under load of 25N, 50N, and 75N at sliding speeds of 400rpm, 500rpm, and 600rpm. uniformity in molecular circulation leads to improved mechanical characteristics. As the strain on the composites grew, so did the coefficient of friction. The friction coefficient decreases as the amount of fly ash in the mixture increases. The wear rate, on the other hand, increased as the load expanded. the effects of tic nforcement on thermal, electrical and Dry sliding wear behaviour of aluminium matrix Nanocomposites M. SIVARAJ1, S.MUTHURAMAN2 to investigate the thermal, electrical &dry sliding wear behaviour of aaluminium matrix composite reinforced with dissimilar particle size (≤ 200 nm and 2 μ m) of titanium carbide particles. Analuminium matrix composite with 0, 5, 10 and 15 vol.% TiC reinforcement was prepared by using powder metallurgy . A pin-on-disc apparatus was broadly used to investigate the wear behaviour of the Al/ TiCnano composites. Wear test was carried out for normal load of 5 N,10 N, 15 N& 20N at constant sliding velocity of 2.61 m/s at room temperature . Hardness value increases with increasing the secondary particle TiC in the Al matrixFor a given load, there is a linear increasein SWR of composites and pure aluminium pinswith sliding distance under dry sliding. The addition of nano sized TiC particles aseinforment in Al matrix was established to embellish the wear resistance significantly The coefficient of friction for the load of 20 N was greater than those for the loads of 10 N& 15 N at constantsliding velocity. However, the coefficient of friction increases as the sliding distance increases.

23. Kamaal Haider et al. investigated the mechanical behavior and fabrication of AA6061 reinforcements of SiC and Al2O3 by the stir-casting process. It is found that the hardness, tensile strength of AA6061/SiC/Al2O3 composite increases with reinforcement contents [1].    Callister et al. evaluated that The structure and properties of the reinforcements (SiC,Al2O3) control the mechanical properties of the composites. Increase in elastic modulus and strength of the composites are reasoned to the strong interface that transfers and distributes the load from the matrix to the reinforcement Further, the improved interface strength and better dispersion of the particles in the matrix can also be achieved by preheating the reinforcements [2].   Kakkar et al. analyzed that silicon carbide (SiC) and Boron carbide (B4C) have a low density and a high hardness in comparison to other reinforcements. During the research, it was analyzed that the hardness and tensile strength increased and due to the addition of 3 to 12% wt of reinforcements [3].

24. Boopathi raman et.al. investigated that Aluminium is widely used for various mechanical application and also have excellent castability properties . But it has some limitation of pure aluminium alloys due to stiffness, wear resistance and lower strength . This limitations can be eradicated by producing hybrid metal matrix aluminium composites with the addition of reinforcement particle . This paper deals with an attempt to study the mechanical behaviour of aluminium hybrid metal matrix composite. The Aluminium 7075 Metal Matrix Composite (MMC) is reinforced (5, 10, 15 Vol. %) with equal amount of Boron Carbide ( B4C ) and Titanium Carbide ( TiC ), fabricated by using stir casting method. Here the micro hardness and the ultimate tensile test is obtained at 15% like 46.10BHN & 220 Mpa [4].  Anand Babu et al. studied the mechanical behaviour of ceramic and fly ash particles reinforcement combined with aluminium based MMCs. The weight contribution of (SiC + aluminium oxide) and fly ash particles were 3, 6, and 9% were utilized for the stir casting method. The combination of 4.5 percentage SiC and fly ash, and aluminum metal alloy reached maximum hardness and tensile when compared with other percentage contribution (3 and 6%). Similarly, the next combination of 4.5 percentage aluminium oxide and fly ash and aluminium base composed maximum hardness and tensile compared to other percentages (3 and 6%). The mechanical results revealed that the porosity range was very low and the particles of reinforcement were homogeneous [5].   

25. Sipway et al explored that Different reinforcements such as TiC , Al4C3, SiC, Al2O3, B4C, TiB2, ZrB , etc can be added but many researchers have mostly used SiC, B4C, and Graphite reinforcements (because the cost of SiC, B4C, and graphite powder is very low) and these have better wettability, besides good mechanical properties in comparison to other reinforcements particles[6]. M.kok et al. investigated that wear resistance of the composites was significantly larger than that of the aluminium alloy , and increased with increasing Al2O3 particles content and size , and wear resistance decreased with increasing the sliding distance, the wear load and the abrasive grit size . The effect of Al2O3 particle size on the wear resistance was more significant than that of the particle content[7].  Guttikonda et.al. studied that , In the fabrication of Al7075 metal matrix composite (MMC), stir casting method is used. In the experimental study it is revealed that the mechanical properties are enhanced by means of heat treatment process and The micro-hardness improved by adding reinforcements to the base alloy . The addition of SiC particles improved wear properties results by the addition of AL2O3 Further the mechanical properties enriched by heat treatment. Micro hardness and tensile strength improved by 34% and 7% by the heat treatment process. Homogeneous mixture of the reinforcement particles with molten metal was observed in the micro structure [8]. 

26. Krishnamoorthi and Balasubramanian reviewed that when the Al7075 is reinforced with various ceramic materials using the techniques such as stir, squeeze casting or ultrasonic casting, powder metallurgy, high energy ball milling and friction stir casting. The properties of the matrix composite such as both mechanical and physical properties are varied and parameters such as reinforcement fraction, particle size and its behaviors during heat treatment and extrusion gets affected. It is also mentioned that there is a significant drop in the density of the matrix composite, an increase in the hardness after reinforcement, increased elastic modulus and tensile strength over its base alloys. The wear rate has increased if applied load and speed are increased [9]. Prasad et al. have investigated by preparing a matrix composite reinforced with magnesium oxide(MgO) using stir casting technique. They have varied the weight percentage of the particles at 5 & 10 have found that tensile properties and hardness and values after reinforcing have increased many-folds than nonreinforced nanoparticles [10]

27. B.N. Sarada et al. studied the hardness and wear loss of Aluminium based hybrid composite manufacturing by a stir casting process. It was found that with the 10% addition of reinforcements activated Carbon and Mica in LM25, the hardness and wear resistance increase in comparison to single reinforcement content [ 11 ] 

28. Materials Used Percent Reinforcements Hardness Tensile Strength Ref. No Al 7075 10Wt.% SiC 1 10BHN 2 29.9MPa 1  Al 6061 12 Wt.% Al2O3 185BHN 195 MPa 2  Al 6061 NiP coated 10 Wt.% Si3N4 86.6BHN 306 MPa 3  AA 6061 10Wt.% B4C 68HV 145 MPa 4  AA 6061 15Wt.% TiC   230 MPa 5  AA 6063 12% Al2O3 & 1%Gr   351.6 MPa 6  Al 6082 12Wt.% Si3N4 93.5VHN 201 MPa 7  AA 6082 10%Wt. WC 83BHN 190 N/mm2 8 A 356 7.5 Wt.% Al2O3 78BHN 164 MPa 9  Aluminium 7 Wt.% Al2O3 63BHN 120 MPa 10  Aluminium 15 Wt.%SiC 52BHN 145 MPa 11  Aluminium 6 &10 Wt.% GSA, SiC 63HRV 166 MPa 12  Aluminium 10 Wt.%SiC 147.2BHN 163 MPa 13  Aluminium 6 Wt.% SiC 88HV 130 MPa 14  Aluminium 20 Wt.% SiC 45.40 BHN 77.56 MPa 15  AA 5083 10 Wt.% SiC 76 BHN 253 MPa 16  LM 25 10% mica & 10% activated Carbon 89.5 BHN - 17  LM 6 10 Wt.% SiC 78BHN   18  LM 25 2wt% Al2O3, 3wt% B4C 52.8BHN 54.6 MPa 19  Table 1: Literature review of various reinforcements in aluminium metal matrix composites

29. . Materials Used Reinforcements Conclusion and Results Ref. No. Al 356 Nano-SiC particles A356 /nano-SiC composite was fabricated by stir casting method. SiC content was distributed uniformly within the matrix. Mixing of 4.5 vol. % of SiC had improved the UTS from 145 to 240 MPa. 13) AA 7075 Nano SiC particles AA 7075/SiC nano composites were manufactured by mechanical stirring and ultrasonic cavitation process. Hardness and impact strength of AA 7075/10%SiC nano composite was improved by 10% and 75 % respectively. 12) Al 6061 Nano Al2O3 particles Al 6061/ Al2O3 composite was prepared by ultrasonic assisted squeeze casting method with avoiding the accumulation of Al2O3particulates. 14) Pure Al TiO2 nanoparticles Al/ TiO2 nano composite specimen was manufactured via powered stir casting technique with avoiding agglomeration of TiO2 nanoparticles. 1 7) Al 6061 Nano ZrO2 content Aluminium-ZrO2 nano composites 7.5% successfully produced by stir casting method. 1 5) AA 7075 SiC+ Al2O3 Nano composites Single and hybrid reinforced nano composites was manufactured via stir and squeeze cast process. Hardness was enhanced by 63.7% and 81.1% for single and hybrid reinforced nano composite.   2 0) Pure aluminum Nano TiO2 The powder metallurgy method was used to prepare Al/ TiO2 composite successfully. Uniform distribution of 40reinforcement was observed. 18) Al-SiC alloy Al2O3-WS2 Increased Wt. % of WS2 solid lubricant had increased the hardness of the hybrid composite. The % of WS2 had increased the density of the composite by filling the gap of the composite. Composites with about 5 percent of WS2 have less pits and worn-out surface as compare to composite without WS2 1 9) Table 3: Literature Review of Aluminium based Nano reinforced Composites

30. S.NO MATERIAL   MANUFACTURING PROCESS   RESULT   1     Al7075 Is Reinforced with Various Ceramic Materials [1]  Stir, Squeeze Casting or Ultrasonic Casting, Powder Metallurgy Friction Stir Casting The density is decreased with reinforcement into the matrix material. The Wear rate of composites increases with increasing applied load and speed and Highest wear rate is obtained for the lower particle size 2   Al7075 With Magnesium Oxide Nano powder (5, 10 wt %) [29]   Stir Casting Technique   At 95 wt % of Al and 5 wt % Of Mgo , Ultimate Tensile Strength = 137.042N/mm2, Hardness Value = 92.07   At 90 wt % Al and 10wt % Mgo Ultimate Tensile Strength = 197.211N/mm2 Hardness Value = 100 (VHN) 3   Al7075 - Tic and Sic (Varying From 0-15 wt %) [2]   Stir Casting Technique   Ultimate Tensile Strength = 240 MPa Corrosion Resistance In 3.5 wt % in Nacl Solution Proving Better Corrosion Resistance (Tested using SEM ) 4   AL7075 - TiC and SiC (90 wt % of Al7075, 4 wt % of TiC,and 8 wt % of SiC ) [3]   Stir Casting Technique   Micro hardness = 52.12 HV. The compression test revealst hat its density has lowest coefficient of friction   5   Al7075 With Tic And Sic (Al7075-5 wt % TiC+5 wt % SiC ) [4]   Stir Casting Technique   Hardness Increased By 39%, ultimate tensile strength = 155 MPa, yield strength = 116 MPa   6   Al7075 With Aluminium Oxide(5%, 10%, 15% Of Al2o3) [5] . Stir Casting Technique   Tensile Strength = 69.519 N/mm2, Micro Hardness = 148.09(VHN) In SEM Analysis Thermal Conductivity Is Higher;Temperature Distribution and Thermal Flux Are Outstanding at 10 wt % Reinforcement  

31. S.NO MATERIAL   MANUFACTURING PROCESS   RESULT   7 Al7075 – Sic (10 wt %) [13]   Stir Casting Technique Sliding speed = 3.77 m/s (ungreased up condition). Sliding speed = 3.14 m/s (greased up condition). Wear rate increments with the typical burden and sliding rate and it is most extreme in latent state of framework amalgam at 30 N.   8   Al7075-T6 with FLY ASH (15, 20, 25wt %) [12] Stir Casting Technique   The SEM images revel that the distribution of the reinforcement fly ash is uniform. The reinforcement of 20% fly ash gives good hardness Highest Hardness value = 80 (BHN)   9   Al7075 – Sic - Al2o3 (2.5, 5, 7.5 wt % OF DIFFERENT COMPOSITIONS OF SIC AND Al2O3) [14]  Stir Casting Technique   The highest hardness value = 130 (BHN). Highest impactable e = 10 J 10   Al7075 - Sic (5, 10, 15wt %) - Magnesium (1 wt %) [8]   Stir Casting Technique   Hardness value =199 (VHN). A Maximum reduction of 27.27% and 54.03% in friction co-efficient and wear rate. 11   Al7075 - Sic (3 wt %) - Al2O3 (3, 6, 9,12wt %) [18]   Stir Casting Technique   Microstructure analysis reveals uniform Distribution. Al7075+12%Al2O3+3% SiC Density= 2752 Kg/m3, Micro Hardness=147.51 300 gmf /13 Sec, Wear=71 micron, Wear Rate=1.26910-4 mm3/ N m, Coefficient of friction = 0.3076  12   Al7075 - SIC (3, 5, 7,9 wt%) Al2O3 (2 wt%) [24].   Stir Casting Technique   The microstructures show the reinforcing particles in the matrix and the solidification pattern. Al7075+9 wt % of SiC+2 wt % of Al2O3 has highest value HARDNESS=119 VHN,UTS =325 MPa and elongation of 2.08.  13   Al7075- sic (size 6.18 μm and 25 wt %) [23]   Stir Casting Technique   Consistent dispersion of SiC particulates in the matrix alloy was observed in the optical micrographs. Around 42% of improvement in grey relational grade has been achieved.  

32. The applications of different reinforcing elements are decided based various considerations such as cost of production, product quality and end application of the product. Powder metallurgy route for AMMCs fabrication offers better kinetics at the interfaces It also helps in reduction in the agglomeration of the reinforcing elements. . It gives the better refinement of the structure by the use rapid solidification of fine powders. Stir casting process for AMMCs are found to economical and provides the net shape product. However, agglomeration of nano particles of reinforcing limits its application in the nano metal matrix composites It was also noticed that the microstructure of the final composite is greatly affected by the fabricating process parameters, type of reinforcing elements and reaction at the interface. Nano reinforce composites possess better strength, hardness and structural integrity then the micro and macro reinforce composites. Important point

33. On the basis of review Some important fi ndings are listed below. 1.Density drop of MMCs caused by adding ceramics as reinforcement with metal matrix 2. It shows that significant increase in the hardness of the metal matrix composite. Further improvement of hardness can be done by heat treatment, temperature ageing process. 3. This type of AMC is found to have higher elastic modulus and tensile strength when compared to base alloys which are being used currently by industries. 4. It is clear that wear rate of composites is increased when applied load and speed are increased. Conclusions

34. References 1.Kamaal Haider, Md. Azad Alam , Amit Redhewal,Vishal Saxena, Investigation of Mechanical Properties of Aluminium Based Metal Matrix Composites Reinforced With SiC & Al2O3, t. Journal of Engineering Research and Applications, ISSN: 2248-9622, Vol. 5, Issue 9, 2015.  2.Callister Jr. W. D., ―Materials Science and Engineering: an introduction‖, New York, Wiley, year 1999. 3.Kakkar K, Jha S, Sharma R, Kamboj K. Study of the Properties of Different Aluminium Metal Matrix Composites-A Review. Proceedings of 3rd International Conference on Manufacturing, Manfex 2016:80-86. 4. Krishnamoorthi , K. and Balasubramanian, P., 2015. Review the Properties of Al7075 Matrix Composites. J. Mater. Sci. Mech. Eng., 2(1), pp.85-90 5.Saravanan S, Senthil Kumar P, Ravichandran M, Anandhakrishnan V and Balan A V., 2017, Processing of aluminium metal matrix composites – A review”, Journal of Manufacturing Engineering,12(3), pp 130-141 6 .M.kok, Kamil Ozadin Wear resistance of aluminium alloy and its composites reinforced by Al2O3 particles 2007Journal of Materials Processing Technology 183(2):301-309

35. 7.Guttikonda manohar , Krishna Murari Pandey, Saikat Ranjan Maity , Effect of processing parameter on mechanical properties on Al7175/ B4C Composite fabricated by powder metallurgy techniques, Advances in Science and technology, ISSN No. 1662-0356, Vol. 105, April 2021. 8. P.H. Shipway, A.R. Kennedy, A.J. Wilkes, ―Sliding wear behaviour of aluminiumbased metal matrix composites produced by a novel liquid route‖, Wear 216 (1998) 160 –171.  9 .Pugalenthi P, Jayaraman M, Natarajan A Evaluation of Mechanical Properties of Aluminium Alloy 7075 Reinforced with SiC and Al2O3 Hybrid Metal Matrix Composites 2015: 766-767   10. .B.N.Sarada, , P.L. Srinivasa Murthy, G. Ugrasen , Hardness and wear characteristics of Hybrid Aluminium Metal Matrix Composites produced by stir casting technique, 4th International Conference on Materials Processing and Characterization, 2 ( 2015 ) 2878 – 2885 11. K. Anand Babu, P. Venkataramaiah , K. Dharma Reddy, Mater. Today: Proc. 5 (2018) 28155–28163

36. 12.Kamaal Haider, Md. Azad Alam , Amit Redhewal,Vishal Saxena, Investigation of Mechanical Properties of Aluminium Based Metal Matrix Composites Reinforced With SiC & Al2O3, t. Journal of Engineering Research and Applications, ISSN: 2248-9622, Vol. 5, Issue 9, 2015.  13 .Callister Jr. W. D., ―Materials Science and Engineering: an introduction‖, New York, Wiley, year 1999. 14.Kakkar K, Jha S, Sharma R, Kamboj K. Study of the Properties of Different Aluminium Metal Matrix Composites-A Review. Proceedings of 3rd International Conference on Manufacturing, Manfex 2016:80-86. 15 . Krishnamoorthi , K. and Balasubramanian, P., 2015. Review the Properties of Al7075 Matrix Composites. J. Mater. Sci. Mech. Eng., 2(1), pp.85-90 16.Saravanan S, Senthil Kumar P, Ravichandran M, Anandhakrishnan V and Balan A V., 2017, Processing of aluminium metal matrix composites – A review”, Journal of Manufacturing Engineering,12(3), pp 130-141 17.M.kok, Kamil Ozadin Wear resistance of aluminium alloy and its composites reinforced by Al2O3 particles 2007Journal of Materials Processing Technology 183(2):301-309

37. [18] J. Hashim, L. Looney, M.S.J. Hashmi,”Metal matrix composites: production by stir casting method”, Journal of Material Processing Technology , 92-93 1999: 1-7 [19] A. R. KENNEDY, A. E. KARANTZALIS, S. M. WYATT,” The microstructure and mechanical properties of TiC and TiB 2 -reinforced cast metal matrix composites” Journal of Materials Science 1999 ; 34 : 933- 940 [20] S. Gopalakrishnan, N. Murugan “ Production and wear characterisation of AA6061 matrix titanium carbide particulate reinforced composite by enhanced stir casting method” Composite : Part B 43 2012 : 302-308 [21] M. Boopathi, K.P. Arulshri , N. Iyandurai “Evaluation of mechanical properties of aluminium alloy 2024 reinforced with silicon carbide and fly ash hybrid metal matrix composites” Am J Appl Sci , 10 (3) (2013), pp. 219–229 [22] D. Siva Prasad, C Shoba “ Hybrid composites – a better choice for wear resistant materials”, J Mater Res Technol , Volume 3 (2),2014,pp-172-178

38. Thermal processing and the (a) effect of different temperature and (b) time of treatments were briefly discussed based on the current literature. Mechanical treatments (wherein the stir casting by mechanical impellers as well as acoustic-based processes are presented); the effect of impeller design and configurations are introduced and that the main influencing aspects of ultrasonic melt treatment are explained. Other methods based on reactive wettings are compactly mentioned (wherein an alloying agent ( e.G. , Mg) addition to al composite melt , is added to a composite slurry to enhance the affinity in interfacial region of reinforcer and matrix . Reinforcing agent is coated by a metal or ceramic ( to prevent melt attack to the strengthening particles ) Wettability improvement Method

39. Cast aluminium alloys Properties required for good casting Low melting temperature Low solubility of gases except H2 Good fluidity Good surface finishes Main disadvantage High solidification shrinkage (3.5-8.5%) Factors controlling properties Melting and pouring practices Impurity levels Grain size Solidification rate Cast aluminium alloys are widely used for transport applications, Eg: Cast engine block

40. IMPORTANT POINT   As the temperature increases, the expansion of the matrix metal is restricted by the reinforcement ; ---Thus, leading to the generation of thermal residual stresses at the matrix/reinforcement interface   consequently, affecting load transfer from the matrix to the reinforcement during high temperature operation .   These residual stresses deteriorate the matrix/reinforcement interface and are often relieved through elastic relaxation and plastic deformation.    Effect of mismatch in thermal expansion coefficient Mismatch in thermal expansion coefficient will surely lead to Residual stresses in both matrix and reinforcement. You could run a simple simulation in ABAQUS, ANSYS or any other software to work out the residual stresses .     Residual stresses are concentrated in the interface region between Matrix and reinforcement. It is irrespective of the shape, size and volume. However, the residual stress in MMCs is depended on the 1.Reinforced particulates sizes 2.shapes and 3.volume.