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# Fabrication of Hybrid Metal Matrix Composite Reinforced With SiC/Al2O3/TiB2

S Johny James, A Raja Annamalai, P Kuppan, R Oyyaravelu

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S Johny James, A Raja Annamalai, P Kuppan, R Oyyaravelu. Fabrication of Hybrid Metal Matrix Composite Reinforced With SiC/Al2O3/TiB2. Mechanics, Materials Science & Engineering MMSE Journal. Open Access, 2017, 10.2412/mmse.66.73.476. [https://hal.science/hal-01504690](https://hal.science/hal-01504690)

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Distributed under a Creative Commons Attribution 4.0 International License
# Fabrication of Hybrid Metal Matrix Composite Reinforced With
SiC/Al₂O₃/TiB₂

S. Johny James¹, a, A. Raja Annamalai², P. Kuppan², R. Oyyaravelu²

1. Kingston Engineering College, Vellore, 632059, India

2. School of Mechanical Engineering, VIT University, Vellore, 632014, India

a. johnyjames2002@yahoo.com

<figure><img src="image_3.png" /></figure>

DOI 10.2412/mmse.66.73.476 provided by Seo4U.link

**Keywords:** Al₂O₃, hybrid metal matrix composite, SiC, TiB₂, wear.

**ABSTRACT.** Looking at the need for composite materials, a trial was made to fabricate hybrid metal matrix composite. Efforts were taken to develop composite with three emerging reinforcements like SiC/Al₂O₃/TiB₂ and its compositions were 5%, 3% and 2% respectively. The aluminium metal matrix designed for this composite is aluminium alloy Al6061. Stir casting bottom pouring technique was used to fabricate the specimen successfully. The fabricated Hybrid metal matrix composite after various attempts was made to undergo various tests to examine its strength and property. Specimen was made from the casting and micro structural analysis was carried out using optical microscope and SEM. Results of micro structural analysis prove the existence and dispersion of reinforcements in the matrix phase. Specimens were prepared in order to test its hardness due to the addition reinforcements. Vickers hardness test and its value which is equal to 122.13 HRC indicate elevated hardness value upto 50% when compare to the hardness value of parent alloy. Tensile specimens were prepared using wire EDM as per ASTM E8 standards. There is no considerable improvement in tensile strength due to addition of above reinforcements. Failure analysis was carried and the factors caused failure was analyzed. In order to study and understand the wear resistance property of Composite which it is mainly known for, wear test was carried out and test results proves the increase in wear resistance property of Composite in terms of frictional force and coefficient of friction.

**Introduction.** Requirement of engineering materials paves the way for invention of advanced materials like super alloys, ceramics, and composites. In these advanced materials Composites have distinguished properties such as increased wear resistance, high specific strength, strength-to-weight ratio, strength to cost ratio etc. This unique property finds application in aerospace, defense, marine, etc. This motivates researchers to fabricate composite with constitution of various reinforcements with aluminum matrix. The addition any one of the reinforcements like SiC, B₄C, Al₂O₃, ZrSiO₄, TiN, and TiB₂ have been carried out and in process as well. Efforts have been initiated to fabricate metal matrix using in situ salt reactions [1]. The stir casting process parameters were thoroughly examined by Pai. It has been concluded that, stir casting process is relatively simple and less expensive as compared to other processing methods [2,3]. Production of composites using stir casting process needs equal distribution of abrasive particles with the metal matrix. S. Balasivanandha Prabu "Influence of stirring speed and stirring time on distribution of particles in cast metal matrix composite". In the present study, high silicon content aluminium alloy-silicon carbide metal matrix composite material, with 10% SiC were successfully synthesized, using different stirring speeds and stirring times.. [4]. Cast composite mainly replace steel and alloys used in aerospace, defense mainly wear resistant applications. Titanium diboride (TiB₂) gives a number of advantages over traditional ceramic reinforcements such as silicon carbide (SiC) or alumina (Al₂O₃). But fabrication of composite reinforced with TiB₂ has number of challenges [5]. During fabrication of TiB₂ chances of formation of cluster is at high side. [6]. TiB₂ has resistance to chemical reaction with Aluminium. The wear
resistance of this material is due to the lack of pull out of this material from the aluminum matrix. TiB2 composites are well known for high wear resistant property when compared to other available ceramic reinforcements [7,8]. This work focuses addition of TiB2, SiC and Al2O3 metal matrix composite. So far SiC and Al2O3 is added with Aluminum matrix but not TiB2. An objective of this study is to harvest the merits of TiB2, SiC and Al2O3. However; most of the existing research work focus on the effect of metal matrix composite with single reinforcement. The present work develops hybrid metal matrix composite. SiC and Al2O3 is widely used reinforcement for composite and it has its own elevated mechanical property. Our present work selects TiB2 as third reinforcement because of its outstanding properties than other existing reinforcements.

**Experimental procedure.** Silicon Carbide, Alumina and Titanium di boride of average particle size 30 micron was used to fabricate Al-SiC-Al2O3-TiB2 metal matrix composite by stir casting bottom pouring technique. The metal matrix selected for this work was Al6061. The melting of aluminium alloy was carried out in a steel crucible located inside the resistance furnace. SiC, Al2O3 and TiB2 particles were preheated at 400°C and 200°C respectively for 90 min to get better wet ability by removing the absorbed hydroxide and added gases. At this molten stage the preheated SiC, Al2O3 and TiB2 particles were added into the crucible. The reinforcement as well as matrix were stirred using mechanical stirrer. The mixed slurry was poured into the mould by bottom pouring technique. Samples were sliced using wire EDM to study the morphology of cast composite. The micro hardness test was carried out by means of Vicker's hardness testing instrument (Matsuzawa MMT-X). The tensile test was performed using INSTRON tensile testing machine. The specimens were prepared as per ASTM-E8 standard Wear test was performed using pin-on-disc reciprocating wear testing equipment

**Results and Discussion**

**Microstructure analysis.** Fig1 (a, b, c, d) shows the SEM and optical image of Al6061/SiC/Al₂O₃/TiB₂ Composite. The SEM and optical image confirms the existence of SiC/Al₂O₃/TiB₂ reinforcements in the metal matrix and its distribution in the metal matrix.

<figure><img src="image_4.png" /><figcaption>Fig. 1, a SEM image of SiC/Al₂O₃/TiB₂.</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Fig. 1, (c) Optical image of SiC/Al₂O₃/TiB₂.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 1, b SEM image of SiC/Al₂O₃/TiB₂.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig. 1, (d) Optical image of SiC/Al₂O₃/TiB₂.</figcaption></figure>
**Cluster formation.** From Fig1 (b, d) it is also observed that there is cluster of reinforcement particle in the metal matrix phase. These cluster formation is one of the main challenge in fabrication of composites using stir casting. As the cluster powders are only reinforcement, during specimen preparation by machining process like EDM, milling etc the reinforcement powders will be poured out which leads to pores. This can be clearly identified using SEM. The black pore which is seen continuously is cluster of reinforcement and the grey phase surrounded by reinforcement is aluminum matrix as shown in SEM image.. This can be prevented by varying stirring speed, holding time and improving wettability between reinforcement and metal matrix phase. Researchers may concentrate in this problem and find a solution to avoid agglomeration.

## Hardness test of Al6061 reinforced with SiC, Al₂O₃ and TiB₂

<table><caption>Table 1. The hardness value.</caption><thead><tr><th rowspan="2">NO</th><th colspan="3">Measurement Position(mm)</th><th rowspan="2">Load</th><th colspan="2">Diagonal(µm)</th><th rowspan="2">Hardness HV</th><th rowspan="2">Conv. Scale</th></tr><tr><th>X</th><th>Y</th><th>Distance</th><th>D<sub>1</sub></th><th>D<sub>2</sub></th></tr></thead><tbody><tr><td>1</td><td>7.639</td><td>-0.427</td><td>7.651</td><td>500</td><td>94.52</td><td>79.31</td><td>122.7</td><td>HRC</td></tr><tr><td>2</td><td>7.232</td><td>-0.356</td><td>7.241</td><td>500</td><td>83.43</td><td>80.44</td><td>138.1</td><td>HRC</td></tr><tr><td>3</td><td>7.549</td><td>-0.303</td><td>7.555</td><td>500</td><td>94.66</td><td>92.67</td><td>105.6</td><td>HRC</td></tr><tr><td colspan="7">Average value</td><td>122.13</td><td>HRC</td></tr></tbody></table>

Addition of reinforcement with aluminum matrix normally increases hardness. In this work SiC, Al₂O₃ and TiB₂ respectively which is named for high hardness was added with the metal matrix. Hardness test was carried out for a load 500gf with a dwell time of 10 seconds. Three readings were taken with standard distance of 0.5mm from every indentation to achieve reliability in results. The average hardness value is 122.13 HRC. The hardness value proves 50% increases in hardness due to the addition of SiC, Al₂O₃ and TiB₂. It has been clearly proved that addition of reinforcements with aluminum matrix increases the hardness value.

**Mechanical testing.** The size of each tensile specimen was 100x10x6 mm. The maximum tensile strength value of cast composite is 0.091Gpa. From table it has been concluded that there is no considerable increase in tensile strength of the cast composite specimen. The cast specimen's strength value will be more if the amount of cluster formation has been controlled by using proper stir casting parameters.

<table><caption>Table 2. The tensile strength of Composite.</caption><thead><tr><th>Weight % of reinforcements</th><th>SL.NO</th><th>Maximum Load (N)</th><th>UTS (GPa)</th><th>Modulus (Automatic Young's) (MPa)</th><th>Proof Stress (MPa)</th></tr></thead><tbody><tr><td>Al6061/SiC-5%</td><td>1</td><td>2697.14594</td><td>0.070</td><td>29806.848</td><td>60.63</td></tr><tr><td>Al₂O₃-3%</td><td>2</td><td>3333.81891</td><td>0.087</td><td>35429.303</td><td>72.66</td></tr><tr><td>TiB₂-2%</td><td>3</td><td>3488.38568</td><td>0.091</td><td>37072.744</td><td>70.74</td></tr><tr><td colspan="6">Maximum value</td><td>0.091Gpa</td></tr></tbody></table>
Fractography

Fig 2(a) and 2(b) shows the SEM image of Al6061/SiC/Al₂O₃/TiB₂ tensile specimen after test. It has been observed from the figure that the reinforcement is evenly distributed in the continuous metal phase of the cast specimen. But a clear, strong interfacial bonding is not seen in between metal and reinforcement phase. This poor interfacial bonding decreased the strength of the composite than the parent metal.

<figure><img src="image_8.png" /><figcaption>Fig. 2. (a) Tensile fracture SEM image.</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>Fig. 2. (b) Tensile fracture SEM image.</figcaption></figure>

The black spot seen in the image 1(d) are reinforcement clusters. The SiC, Al₂O₃, TiB₂ particles mix together and forms cluster. The cluster formed surface lack interfacial bonding with aluminum matrix. As this cluster formation leads to pores and poor interfacial bonding tensile test results are adverse and substantial reduction in strength of composite to 0.091Gpa.

Wear test

Wear test was carried to find out wear resistant property of composite for the purpose which is well known for. The table tabulates COF and FF which is 0.668, 33.483N respectively. Additions of reinforcements like SiC, Al₂O₃, increases wear resistance property. The hard reinforcement particles especially TiB₂ and its high wear resistant property prevent the aluminium matrix from wear.

<table><caption>Table 5. Shows the value of COF and Frictional Force during wear test.</caption><thead><tr><td>COF</td><td>FF(N)</td><td>TEMP(°C)</td><td>LOAD(N)</td><td>SPEED</td><td>Wear in um</td></tr></thead><tbody><tr><td>0.668</td><td>33.483</td><td>34</td><td>50</td><td>608</td><td>128.298</td></tr></tbody></table>

**Summary.** Materials required to fabricate hybrid metal matrix composite was perfectly chosen and fabricated using stir casting process. Microstructure and spectrum processing shows the distribution and existence of SiC, Al₂O₃, and TiB₂ in the metal matrix. Hardness test proves improvement of hardness value approximately 50% due to the addition of reinforcements in the metal matrix phase. Tensile test was carried out and tensile strength was measured. The low value depicts poor bonding between reinforcement and metal matrix which is clearly once again proved by fractography. Wear resistant property which is one of the peculiar properties of Composite has been achieved due to addition of three reinforcements especially TiB₂ in metal matrix Al 6061. Above fabrication and tests
ensure the attainment of superior mechanical and tribological property of cast hybrid metal matrix composite using stir casting process.

References

[1] Kumar, S., Chakraborty, M., Sarma, V. S., & Murty, B. S. (2008). Tensile and wear behaviour of in situ Al-7Si/TiB2 particulate composites. Wear, 265(1), 134-142.

[2] Pai, B. C., Pillai, R. M., & Satyanarayana, K. G. (1993). Stir Cast Aluminium Alloy Matrix Composites. In Key Engineering Materials (Vol. 79, pp. 117-128). Trans Tech Publications.

[3] Hashim, J., Looney, L., & Hashmi, M. S. J. (1999). Metal matrix composites: production by the stir casting method. Journal of Materials Processing Technology, 92, 1-7.

[4] Prabu, S. B., Karunamoorthy, L., Kathiresan, S., & Mohan, B. (2006). Influence of stirring speed and stirring time on distribution of particles in cast metal matrix composite. Journal of Materials Processing Technology, 171(2), 268-273.

[5]. Watson, I. G., Forster, M. F., Lee, P. D., Dashwood, R. J., Hamilton, R. W., & Chirazi, A. (2005). Investigation of the clustering behaviour of titanium diboride particles in aluminium. Composites Part A: Applied Science and Manufacturing, 36(9), 1177-1187.

[6] Smith, A. V., & Chung, D. D. L. (1996). Titanium diboride particle-reinforced aluminium with high wear resistance. Journal of materials science, 31(22), 5961-5973.

[7] Taya, M., Hayashi, S., Kobayashi, A. S., & Yoon, H. S. (1990). Toughening of a Particulate-Reinforced Ceramic-Matrix Composite by Thermal Residual Stress. Journal of the American Ceramic Society, 73(5), 1382-1391.

[8] Mc Murtry, C. H., Boecher, W. D. G., Seshardri, S. G., Zanghi, J. S., & Garnier, J. E. (1987). Microstructure and material properties of SiC-TiB/sub 2/particulate composites. Am. Ceram. Soc. Bull.;(United States), 66(2).

Cite the paper

S. Johny James, A. Raja Annamalai, P. Kuppan, R. Oyyaravelu (2017) *Fabrication of Hybrid Metal Matrix Composite Reinforced With SiC/Al2O3/TiB2*. *Mechanics, Materials Science & Engineering*, Vol 9. Doi 10.2412/mmse.66.73.476