Due to the demand for lightweight materials in the field of automobiles, aeronautics and some other application, there is a need to develop lightweight materials. For the last few decades, aluminum matrix co mposites are being developed in order to meet out the demand of the above -mentioned industries. aluminum the above, lightweight material in the form of composites of B4C reinforced in Al7075 alloy is considered for the present investigation. The composite was produced using the stir casting method. In this investigation, the micro and nano B4C particles were used as reinforcements. The fabricated composites were characterized for microstructure and mechanical properties. From the microstructural examination, it was observed that 12% of B4C nanocomposites was having fine microstructure as compar ed to others. The hardness and strength were found to be maximum for 12 % B4C nanocomposites which impact strength was lowest for 12% micro composites. Keywords: Al7075 alloy, B4Cp, Stir casting, and UTS . Cite this Article: Krishna Mohan Singh and A. K. Chauhan , Comparison of mechanical and microstructural examination of Al7075 composites reinforced with micro and nano B4C, International Journal of Mechanical Engineering and Technology 11(4), 2020, pp. 08-15 http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=11&ITy pe=4 1. INTRODUCTION Aluminum matrix composites are being used in various fields such as automobiles, aerospace marine, etc. due to their favorable properties [1]. An alloy of the Al7075 series is having the highest strength to weight ratio. This properly makes Al7000 series alloys a good option for reinforcement. The reinforcement can be a ceramic oxide, nitride ca rbide particulates. These reinforcements are improving the properties of Al7000 series alloys [2],[3],[4]. In an investigation, Al7075 alloy was reinforced with LM 13 aluminum/ B4C by means of liquid metallurgy techniques to find the wear behavior [5]. V. Ramakoteswara Rao et al [6] have synthesized Aluminium matrix composites reinforced with titanium carbide particles to find the sliding wear behavior . E. Zalenhad and A.D. Sachan investigated fretting fatigue resistance of Al7075 -T6 with surface treatment of Ti -TiN multilayer coating [7]. The Impact of Share Cropping System on the Productivity of Rice Farming in Central Java http://www.iaeme.com/ IJMET/index. asp 9 editor@iaeme.com From most of the investiga tion done by various researchers, it was observed that the composite of the Al7000 series is made by casting technique [8]. Harichandran and Selvakumar instigated that mechanical properties such that impact energy was higher in composites having nano reinforcement as compared to composites having micro reinforcement [9]. Daniel et al [10] having investigated the influence of wt. percentage of SiC particles reinforced in aluminum metal matrix comp osites. Nagral et al [11] have reported that Al2024 alloy composites were manufactur ed with B 4C particles using a stir casting technique. Singh and Chuahan [12] have reported about the second generation of composites. They reported that hybrid aluminum matrix composites are belonging to second -generation composites. According to the second generation, composites have substantial potential as an alternative to Singh reinforced composites. AA707 5 matrix was reinforced with TiC particles through the stir casting technique [13]. The investigators found the effect of load on the friction and wear of matrix as well as composites. In a research paper, the authors developed a statistical model to envisage vibration amplitude [14]. Dhokey and Rane have applied aluminum -based TiB 2 reinforced composites as brake drum material. They observed that the wear behavior of the composites was considerably good in correlation with its mechanical properties [15]. In the present investigation Al7075 alloy has been used as a matrix. This was reinforced with micro and nano B4C particles. The composit es were characterized in terms of microstructure and mechanical properties, 2. MATERIAL S Al7075 alloy was selected as a composites matrix . micro and nano B4C chosen for the fabrication of the composites reinforcement particle . The composites were manufactured by stir casting techniques . The Al 7075 alloy framework made of Al7075 w as melted in a vacuum furnace for the preparation of the composites . After passing through a sieve for each composite, weighted and preheated dispersoi ds of size between 50 μm and 90 nm with 6, 8, 10 & 12 weight % were poured into the melt . The melt was con tinuousl y stirrer during the insertion of the dispersoid, using a stirrer put in the melt driven by a motor. 3. STIR CASTING TECHNIQUES The vacuum fu rnace (Fig.1) was used to produce the composites. A scattered phase ( micro and nano B 4C particles) was inserted in molten metal . The stir was used to uniformly distribute the reinforcement particles. Figure 1 Experimental setup for fabricating Al7075 and B4C particle s. Comparison of mechanical and microstructural examination of Al7075 composites reinforced with micro and nano B4C http://www.iaeme.com/ IJMET/index. asp 10 editor@iaeme.com 4. MICR OSTRUCTURAL AND MECHANICAL PROPERTIES The microstructure was examined using an optical microscope. XRD spectra were performed on the composites to find the crystal structure. T he hardness was measured using a Brinell Hardness Tester. The load and dwelling times applied were 18 7.5 kgf and 5s, respectively. Tensile experiments were c onducted on a Universal Testing Machine (UTM). The tests were performed as per the ASTM E8 standard. The impac t tests were carried out on an impact testing machine . The impact tests were performed as per the ASTM E23 standard. 5. RESULT AND DISCUSSION 5.1. Compositional analysis The compositions of the Al7075 and B 4C are shown in Tables 1 and 2 respectively. Table 1 Chemical analysis of Al 7075 alloy. Elements Zn Mg Cu Fe Cr Al % by wt. 5.8 2.4 1.5 0.2 0.2 Balance Table 2 Chemical analysis of B4C micro powder (50µm) and nanopowder (90nm). Elements Assay Boron Carbide O N Si Ni % by wt. 99.9 77.2 22.3 <0.1 <0.08 <0.1 <0.01 5.2. Microstructural Examination Fig. 2, show the microstructure of Al7075 and Fig. 3 and Fig. 4, show the microstructure of the Al7075 with micro and nano B 4C respectively . The analysis of microstructure clearly shows that the surfaces are transparent with few porosities. The investigation into Optical microscope micrographs shows that microstructure consists of a uniform distribution of micro B 4C particles and intermetallic comp ounds scattered along the grain boundary in the Al7075 alloy matrix. Uniform micro - and nano B4C particle dispersal and better bonding within Al7075 improve the properties. Al7075 alloy Figure 2 The microstructure of Al7075 alloy The Impact of Share Cropping System on the Productivity of Rice Farming in Central Java http://www.iaeme.com/ IJMET/index. asp 11 editor@iaeme.com Al7075 -6 wt. % of micro B4C Al7075 -8 wt. % of micro B4C Al7075 -10 wt. % of micro B4C Al7075 -12 wt. % of micro B4C Figure 3The microstructure of Al7075 with micro B4C. Al7075 -6 wt. % of nano B4C Al7075 -8 wt. % of nano B4C Comparison of mechanical and microstructural examination of Al7075 composites reinforced with micro and nano B4C http://www.iaeme.com/ IJMET/index. asp 12 editor@iaeme.com Al7075 -10 wt. % of nano B4C Al7075 -12 wt. % of nano B4C Figure 4 The microstructure of Al7075 with nano B4C. 5.3. X-ray diffraction analysis Figure 5 XRD of Al7075 alloy with wt. % micro B4C. 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85050000100000150000 B4CZn B4CAlIntensity (count/sec.) 2 (degree )Al7075+ 6 wt.% micro B4C Al 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85050000100000 B4C B4CZnAlIntensity (count/sec.) 2 (degree)Al7075 + 8 wt.% micro B4C Al 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85050000100000150000 B4CB4CZnAlIntensity (count/sec.) 2 (degree )Al7075 + 10 wt.% micro B4CAl 15 20 25 30 35 40 45 50 55 60 65 70 75 80 8502000040000 B4CB4CZnAlIntensity (count/sec.) 2 (degree )Al7075 + 12 wt.% micro B4CAl The Impact of Share Cropping System on the Productivity of Rice Farming in Central Java http://www.iaeme.com/ IJMET/index. asp 13 editor@iaeme.com Figure 6 XRD of Al7075 alloy with wt. % nano B4C Fig. 5 and Fig. 6 respectively, indicate X-ray diffraction spectra of as -cast Al7075 alloy and reinforced with micro and nano B 4C. The XRD analysis study reveals that the height of the peak shows the presence of elements as mentioned. 5.4. Tensile Tests Fig. 7 Demonstrates a comparative bar graph of AMCs reinforced with B 4Cp of 6, 8, 10 and 12 % micro and nano B4C. The increase in the tensile strength of AMCs containing nano B4Cp is due to the strengthening of th e matrix. Figure 7 Comparative bar chart for UTS of Al7075 and its composites. 15 20 25 30 35 40 45 50 55 60 65 70 75 80 8502000040000 B4CB4C B4CMgZnAlIntensity (count/sec.) 2 (degree)Al7075+ 6 wt.% nano B4CAl 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85050000100000 B4CZnAlIntensity (count/sec.) 2 (degree)Al7075+ 8 wt.% nano B4C Al MgB4C 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850200004000060000Intensity (count/sec.) 2 (degree )Al7075+ 10 wt.% nano B4CAl Al Zn Zn B4CB4CCu 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85020000400006000080000Intensity (count/sec.) 2 (degree )Al7075+ 12 wt.% nano B4C Al Al ZnZn B4CMg Cu050100150200250 0 wt. % 6 wt. % 8 wt. % 10 wt. % 12 wt. %Ultimate Tensile Strength (UTS)B4C(wt. %)Ultimate Tensile Strength (UTS) Specimen Standard: ASTM E8 Al7075 alloy Al7075+ micro B4C Al7075+ nano B4C Comparison of mechanical and microstructural examination of Al7075 composites reinforced with micro and nano B4C http://www.iaeme.com/ IJMET/index. asp 14 editor@iaeme.com 5.5. Hardness Test Fig. 8 indicates the effect of the particle content of micro and nano B 4C on the hardness of the micro and nano B 4C reinforced composites . The values of hardness seem to depend on the weight of micro and nano B 4Cp. The composites made with nano B4C are having th e same what higher hardness. With the addition of 12 wt .%, the hybrid composites reach optimum hardness. Figure 8 Comparative bar chart for BHN of Al7075 and its composites . 5.6. Impact test The toughness value of the alloy and t he composites is shown in Fig. 9. It is observed that there is a decrease in toughness due to an increase in the volume fraction of reinforcements. Figure 9 Comparative bar chart for Impact strength of Al7075 and its composites . 6. CONCLUSIONS The micro and nano B 4Cp reinforced with Al7075 were produced using stir - casting . The composites were examined to investigate the effect of various weight percentages of micro and nano B 4Cp on the microstructure and mechanical properties of the composites . The nanocomposites having higher strength than that of micro composite and Al7075 alloy The impact energy of nano B4Cp reinforced aluminum composites was higher than that of micro B 4Cp reinforced Al7075 composites. 020406080 0 wt. % 6 wt. % 8 wt. % 10 wt. % 12 wt. %Imact Strength B4C (wt. %)Imact Energy (Charpy Test) Specimen Standard: ASTM E23 Al7075 alloy Al7075+ micro B4C Al7075+ nano B4C The Impact of Share Cropping System on the Productivity of Rice Farming in Central Java http://www.iaeme.com/ IJMET/index. asp 15 editor@iaeme.com