In present work, the effects of hybridizing micron sized B4C particles with multi walled carbon nanotubes on the microstructural and mechanical properties of Al - B4C composite were investigated. Microstructure reveals grain refinement ascribed to the presence of uniformly distributed micron sized B4C particles with multi walled carbon nanotubes. The Al - (B4C + MWCNT) hybrid composite indicates the alliance of mechanical properties such as hardness, tensile strength and ductility. The enhanced attribute of Al - (B4C + MWCNT) hybrid composite when compared to Al - B4C is the increased content and uniform distribution of MWCNTs. Â© Published under licence by IOP Publishing Ltd

Arjun, R.

Khan, M.A.

Nadeem Pasha, K.

Sharieff, S.

Zakaulla, M.

IOP Conference Series : Materials Science and Engineering

ePrints@Bangalore University

IOP Conference Series: Materials Science and EngineeringPAPER • OPEN ACCESSHybridizing Micro - B4C With Carbon nanotubes toEnhance The Mechanical Properties of AluminiumMatrix CompositesTo cite this article: Mohamed Zakaulla et al 2017 IOP Conf. Ser.: Mater. Sci. Eng. 225 012234 View the article online for updates and enhancements.Related contentComputational simulation of a diffusionprocess of carbon nanotubes in aluminiumto improve the mechanical properties of acomposite materialG Suárez Guerrero, M F Valencia-García,H V Martínez Tejada et al.-A Brief Research Review for ImprovementMethods the Wettability between CeramicReinforcement Particulate and AluminiumMatrix CompositesAlaa Mohammed Razzaq, Dayang LailaAbang Abdul Majid, M.R. Ishak et al.-Mechanical Properties of Single-Walled(5,5) Carbon Nanotubeswith VacancyDefectsYuan Shi-Jun, Kong Yong and Li Fa-Shen-This content was downloaded from IP address 177.142.115.112 on 14/03/2018 at 23:511Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd1234567890ICMAEM-2017 IOP PublishingIOP Conf. Series: Materials Science and Engineering 225 (2017) 012234 doi:10.1088/1757-899X/225/1/012234 Hybridizing Micro - B4C With Carbon nanotubes to Enhance The Mechanical Properties of Aluminium Matrix Composites. Mohamed Zakaulla, Arjun R, Muzakkir Ahmed Khan, Nadeem Pasha K, Salim Sharieff. Associate professor, Department of Mechanical engineering, H.K.B.K.C.E, Bangalore, India Research scholar, Department of Mechanical engineering, University Visvesvaraya college of engineering, Bangalore, India Assistant professor, Department of Mechanical engineering H.K.B.K.C.E, Bangalore, India Research scholar, Department of Mechanical engineering, University Visvesvaraya college of engineering, Bangalore, India Research scholar, Department of Mechanical engineering, University Visvesvaraya college of engineering, Bangalore, India  Abstract: In present work, the effects of hybridizing micron sized B4C particles with multi walled carbon nanotubes on the microstructural and mechanical properties of Al - B4C composite were investigated. Microstructure reveals grain refinement ascribed to the presence of uniformly distributed micron sized B4C particles with multi walled carbon nanotubes. The Al - (B4C + MWCNT) hybrid composite indicates the alliance of mechanical properties such as hardness, tensile strength and ductility. The enhanced attribute of Al - (B4C + MWCNT) hybrid composite when compared to Al - B4C is the increased content and uniform distribution of MWCNTs.  Keywords: Ductility, Hybrid composite, Hardness and Tensile strength. 1. INTRODUCTION Aluminium being a light metal is studied with much attention as structural material, though they lack in rigidity and strength when compared with iron.  Al2024 alloy has high strength to weight ratio, good fatigue resistance, average machinabiity and high strength. Its application involves wing structures in aircraft. Boron carbide is the hardest material and has properties such as low density and good chemical resistance.  MWCNTs are used strength additives for polymer, ceramic and metallic composites due to high stiffness and strength. Metal matrix/ ceramic/ CNT composites have a great potential in automobile, space craft and VLSI industry due to high hardness, less coefficient of thermal expansion and high specific strength.  Amal and Mostafa [1] investigated the attributes of Al- CNT strips and Al – 0.5wt% CNT strips exhibited improved yield strength, tensile strength and low density.  Pulickel and Zhou [2] reported that CNT structures are remarkable and hence they are used in wide range of applications. Prabhu and Vinayagam [3] studied that MWCNTs helps improving the surface features from micro to nano level when used in grinding process. Yufeng Wu and Gap yong kim [4] obtained a hardness value of 87.5HV at 620°C for Al6061-CNT composite. Lai xue pang et al [5] developed Fe3Al-CNT composite at 1273k and pressure 30 Mpa. The value for microhardness and compressive strength was 8.7 Gpa and 3175Mpa for 5% CNT in the composite. Bradbury et 21234567890ICMAEM-2017 IOP PublishingIOP Conf. Series: Materials Science and Engineering 225 (2017) 012234 doi:10.1088/1757-899X/225/1/012234al  [6] studied aluminium composite with 6 wt% of CNT preared by milling and concluded that maximum hardness was achieved due to MWCNTs. Dehong Lu et al [7] studied AZ31 composite reinforced with 0.1% Al2O3 and 0.2% CNTs and concluded that composite showed less wear for less load. Choi et al [8] investigated the aluminium nano composite reinforced with 5wt% Si alloy and 3 vol% MWCNTs and there was a improvement in % elongation and yield strength. Liu et al [9] reported that CNTs strength improved when ball milling time was 6 hours. Sebastian et al [10] fabricated Ni- MWCNT composite and was no improvement beyond 3 wt% of CNT because CNTs reagglomerated for large volume fraction. Bustamante et al [11] reported that when 5 wt% CNT content was added to Al 2024 composite it showed improved wear properties.   In the present work, hybrid composite is fabricated using stircasting technique and matrix used is Al2024 and reinforcements are micro B4C and MWCNTs. The obtained composites are investigated for microstructure and mechanical properties such as hardness, tensile strength and ductility. Finally SEM is used for analyzing fractured specimens of composite. 2. EXPERIMENTAL PROCEDURE  The material used for fabricating hybrid composite is Al2024 which is in form of billets, reinforcements such as B4C of size 30 microns and MWCNTs. Initially Al2024 is made in to small billets and melted in a Electric resistance furnace at a temperature of 700°C. Degassing agent (hexachlore ethane) was used for reducing gas porosities. 10 wt% of Boron carbide particles and MWCNTs of 1wt% and 2wt% were mixed in ball mill and preheated for 3 to 4hours at 450°C. Preheated reinforcements was added in to melts and mixed for 5 mins using a stirring bar.  Finally molten composite slurry is poured in to metallic mould and allowed to solidify.  3. RESULTS AND DISCUSSION  3.1 Microstructure The presence and distribution of B4C particles and MWCNTs in Al2024 matrix were studied using optical microscope. Fig 1 (a) shows the equiaxed grains in the Al2024 sample. Fig 1(b) shows the Al2024-10%B4C composite and it is seen that B4C are uniformly distributed in the matrix.  Fig1(c) and Fig 1(d) shows the microstructure of Al2024-10%B4C-1%MWCNTs and Al2024-10%B4C-2%MWCNTs composite. It is seen that crystal grains of composite with 1% MWCNTs is coarser than 2% MWCNTs content.        31234567890ICMAEM-2017 IOP PublishingIOP Conf. Series: Materials Science and Engineering 225 (2017) 012234 doi:10.1088/1757-899X/225/1/012234                          (a) Al2024                       (b) Al2024+ 10% B4C                                                                     (c)  Al2024+ 10% B4C + 1%MWCNTs                             (d)  Al2024+ 10% B4C +2%MWCNTs  Fig.1 Microstructure of Al2024 hybrid composite  3.2 Hardness Hardness of a composite is determined as per ASTM E10 standards. A test load of 500Kg is enforced on the specimens for 30sec. The average of all the eight readings is taken as hardness of the sample. The diameter of the steel ball indenter is 10mm. Fig 2 shows the hardness of Al2024 hybrid composite. It is seen that by addition of 10wt% of B4C particles the hardness of the composite is increased because of the high hardness value of boron carbide as a ceramic and protects the specimen surface. It is also seen that with the increased content of MWCNTs the hardness is increased since they are uniformly distributed and MWCNTs provide deformation resistance to the movement of dislocation. The Brinell hardness for Al2024 sample is 100.35 BHN and for only 10%B4C sample has 113.13 BHN and for 1% MWCNTs and 2% MWCNTs with 10%B4C has 116.59 and 125.03 BHN respectively.  41234567890ICMAEM-2017 IOP PublishingIOP Conf. Series: Materials Science and Engineering 225 (2017) 012234 doi:10.1088/1757-899X/225/1/012234 Fig. 2  Hardness of Al2024 hybrid composite  3.3 Tensile strength   Fig 3 shows the results of tensile test for hybrid composite reinforced with 10wt% B4C and different wt% of MWCNTs. Tensile test was conducted from tensometer according to ASTM E8 standards and four readings was taken as a average. It is observed that 10wt% B4C + 2%MWCNTs provides the most significant strengthening (+43%) followed by 10wt%  B4C + 1%MWCNTs provides 32% and finally 10wt%  B4C provides 20%   in compare to Al2024 alloy. Improvement in tensile strength is mainly due to better dispersion of CNTs and B4C provided by ball miling and in addition to the strain hardening which contributes to the final strength of the composite there is a mismatch of elastic and thermal expansion coefficients between matrix and reinforcements (αAl2024 – 22.8 X10-6 °C-1,   αB4C – 5 X10-6 °C-1, αMWCNTs – 0.73X10-5 °C-1 ) which contributes to the strength of composite.   Fig. 3 Tensile strength of Al2024 hybrid composite 020406080100120140BHN020406080100120140160180200Tensile strength51234567890ICMAEM-2017 IOP PublishingIOP Conf. Series: Materials Science and Engineering 225 (2017) 012234 doi:10.1088/1757-899X/225/1/012234 3.4  Ductility and fractography  Fig 4 shows the % elongation for Al2024 hybrid composite. Al2024 alloy and as 10wt% B4C is added to base alloy the ductility decreases because presence of hard ceramic phase which leads to localized crack initiation and stress concentration sites at the matrixMWCNTs with 10wt% B4C to Al2024 alloy leads to improvement in ductility becausestressed state there is a resistance to plastic deformation of dislocations and it increases for nano structu(a) Al2024                                                 02468101214% ElongationThere is larger elongation for - reinforcement interface. Addition of different wt% of which is due to difficulty in rearranging res which have less generated dislocationFig. 4 % Elongation of Al2024 hybrid composite shows the SEM fractographs of Al2024 hybrid composite. The Al2024 alloy shows large and deep dimples on the fracture surface which indicates ductile fracture.  fig 5 (b)10wt% B4C which has areas of brittle fracture which is due to the particles from Al2024 matrix. The fracture surfaces of fig 5(c) and 5(d)shows a lot of dimples indicating the ductile nature of fracture which means that interfaces C particles and MWCNTs are very strongly bonded.                   (b) Al2024+ 10% Bof  in a .   shows the   4C  Fig 5 composite reinforced with decohesion of B4C between the matrix, B4           61234567890ICMAEM-2017 IOP PublishingIOP Conf. Series: Materials Science and Engineering 225 (2017) 012234 doi:10.1088/1757-899X/225/1/012234           (c)  Al2024+ 10% B4C + 1%MWCNTs             Fig. 5 Fracture surface of Al2024 hybrid composite 4. CONCLUSIONS  In this study, composites with B4C particles and by using stir casting technique. The samples results are as follows 1) B4C particles and MWCNTs are uniformly distributed in the Al2024 matrix and there is no agglomeration of MWCNTs in the composite.2) The max Brinell hardness number was obtained for Al2024the value is   125.03 BHN.3) Al2024-10wt% B4C + 2%MWCNTs provides strengthening (+43%) in compare to Al2024 alloy. 4) The fracture surface of composite rindicates a ductile fracture which means particles and MWCNTs are very strongly bonded5. REFERENCES  [1] Amal M.K. Esawi, Mostafa A. El Borady, Carbon nanotubeComposites Science and Technology, 68, (2008), PP. 486[2] Pulickel M. Ajayan and Otto Z. Zhou, Applications of Carbon Nanotubes, International Material reviews (2001). [3] S Prabhu, and B K Vinayagam, Nano Surface Generation of GrinNano Tubes, Indian Academy of Sciences, Vol. 35, Part 6, (2010). PP 747[4] Yufeng Wu, Gap-Yong Kim,Carbon nanotube reinforced aluminium composite fabricated by semi-solid powder processing, Journal of Materials Processing Te1341–1347.             (d) Al2024+ 10% B4C +2%MWCNTs 1% - 2% MWCNTs were successfully preparedwas subjected to mechanical tests and the various  -10%B4C-2%MWCNTs and  einforced with B4C particles and MWCNTs that interfaces between the matrix, . -reinforced aluminium strips, –492. ding Process Using Carbon –760  chnology 211 (2011), PP   B4C 71234567890ICMAEM-2017 IOP PublishingIOP Conf. Series: Materials Science and Engineering 225 (2017) 012234 doi:10.1088/1757-899X/225/1/012234[5] Lai-Xue Pang, Kang-Ning Sun, Shuai Ren, Chang Sun, Run-Hua Fan, Zhi-Hua Lu, Fabrication and microstructure of Fe3Al matrix composite reinforced by carbon nanotubes, Materials Science and Engineering: A, Volume 447, Issues 1–2, 25 Feb 2007, PP 146-149. [6]  Christopher R. Bradbury, Jaana-KateriinaGomon, LauriKollo, Hansang Kwon, Marc Leparoux, Hardness of Multi Wall Carbon Nanotubes reinforced aluminium matrix composites, Journal of Alloys and Compounds 585 (2014), PP 362–367. [7] Dehong Lu, Yehua Jiang, Rong Zhou, Wear performance of nano-Al2O3 particles and CNTs reinforced magnesium matrix composites by friction stir processing, Wear, Volume 305, Issues 1–2, 30 July 2013, PP 286-290. [8] H.J. Choi, J.H. Shin, B.H. Min, D.H. Bae, Deformation behaviour of Al–Si alloy based nanocomposites reinforced with carbon nanotubes, Composites: Part A 41 (2010), PP 327–329. [9] Z.Y. Liu, S.J. Xu, B.L. Xiao, P. Xue, W.G. Wang, Z.Y. Ma, Effect of ball-milling time on mechanical properties of carbon nanotubes reinforced aluminium matrix composites, Composites: Part A 43 (2012), PP 2161–2168. [10] Sebastian Suarez, Federico Lasserre, Frank Mücklich,Mechanical properties of MWNT/Ni bulk composites: Influence of the microstructural refinement on the hardness, Materials Science & Engineering A 587 (2013), PP 381–386. [11] R. Pe´rez-Bustamante, J.L.Bueno-Escobedo, J.Jime´nez-Lobato, I.Estrada-Guel, M. Miki-Yoshida, L.Licea-Jime´nez, R.Martı´nez- Sa´nchez,Wear behaviour in Al2024–CNTs composites synthesized by mechanical alloying, Wear 292–293 (2012), PP 169–175. 

Hybridizing Micro - B4C with Carbon nanotubes to Enhance the Mechanical Properties of Aluminium Matrix Composites

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Hybridizing Micro - B4C with Carbon nanotubes to Enhance the Mechanical Properties of Aluminium Matrix Composites

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