Microstructural Studies of Al Al2O3 Nanocomposites Prepared by Powder

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1 Microstructural Studies of Al Al2O3 Nanocomposites Prepared by Powder Metallurgy Route K. Dash*, D.Chaira and B.C. Ray Department of Metallurgical & Materials Engineering National Institute of Technology Rourkela, Rourkela , India

2 OVERVIEW Introduction to nanocomposites Why Al-Al2O3? Applications Microcomposite vs nanocomposites Experimental design Mechanism of SPS XRD Accommodation factor Particle size ratio SEM TEM AFM Density, microhardness and nanohardness Conclusions References

3 AN INTRODUCTION TO NANOCOMPOSITES 1. Small filler size: High surface to volume ratio Small distance between fillers bulk interfacial material 2. Mechanical Properties Increased ductility with no decrease of strength, Scratching resistance 3. Optical properties Light transmission characteristics particle size dependent CRITICAL ISSUES IN NANOCOMPOSITES Dispersion Alignment Volume and rate Cost effectiveness Interface study Even god knew composites would create magic Supercritical applications of nanocomposites

4 Why Al Al2O3? The system shows high stability at elevated temperatures. The system resists softening at high temperatures. Alumina does not react with matrix at high temperature and does not create any undesired phase. The system has superior properties such as hardness, fracture toughnessas compared to the native material. High thermal stability of alumina particles prevents the particles fromripeningand dissolving. Native aluminum s wear resistance is poor and alumina helps in enhancing the same. APPLICATIONS

5 Micro composites Strength Ductility Higher Inter-particle distance Higher Dislocation immobilization Lower Dislocation density Higher Higher Nano composites

6 EXPERIMENTAL DESIGN Blending of as received powders Spark Plasma Sintering Density esy measurement Crystal structure t Internal structure Characterization Properties Morphology Interface

7 Proposed mechanisms of Spark plasma sintering Spark impact pressure Plasma cleaning of particle surfaces Joule heating Local melting and evaporation Surface activation on the particles Electron wind force Field assisted diffusion Pulsed current flow through powder particles The on-off DC pulse energizing method generates Spark plasma Spark impact pressure Joule heating Electrical field diffusion effect

8 X-RAY DIFFRACTION STUDY [200] Al [603] Al2 O 3 [220] Al [311] Al [222] Al [111] Al ) [111 ] Al (in arb units) [200] Al 7% Alumina 5% alumina 1% Alumina Intensity [012] Al 2 O 3 [104] Al 2 O [113] Al [024] Al [116] Al [300] Al 3 O 2 3 O O 3 2 O 3 [220] Al [311] Al [222] Al Intensity (in arb units Theta (in deg) Theta (in deg) Microcomposite Nanocomposites

9 ACCOMODATION FACTOR

10 PARTICLE SIZE RATIO(PSR) Ordered Random Clustered PSR = The ratio of reinforcement particle size to the matrix particle size PSR ~ 1 (lower is the possibility of clustering) CLUSTERING = f (relative sizes of metal and reinforcing particles) f (volume fraction of reinforcement) f (processing route) OFF-SHOOTS OF CLUSTERING Deformation and fracture Damage initiation and accumulation Fracture toughness Flow stress and work hardening

11 SCANNING ELECTRON MICROSCOPY

12 NANO MICRO

13 TRANSMISSION ELECTRON MICROSCOPY NANOCOMPOSITES MICROCOMPOSITE

14 SAD PATTERNS EDX ANALYSIS

15 ATOMIC FORCE MICROSCOPY NANOCOMPOSITE 3D IMAGING MICROCOMPOSITE

16 SECTION ANALYSIS NANOCOMPOSITE MICROCOMPOSITE

17 ROUGHNESS ANALYSIS PEAK AND VALLEY MEASUREMENT

18 DENSITY MICROHARDNESS &NANOHARDNESS Al-Al 2 O 3 nanocomposites Al-Al 2 O 3 microcomposite 1.0 nanohardness of Al 2 O 3 nanocomposites nanohardness ofal 2 O 3 microcomposite microhardness of Al 2 O 3 nanocomposites microhardness of Al 2 O 3 microcomposite Densification (% %) Vol % of alumina Al-Al 2 O 3 Nanocomposites Al-Al 2 O 3 Microcomposite Theoritical values Hardne ess(in GPa) Vol percent of alumina Elastic modulus ( in GPa) Vol percent of alumina

19 CONCLUSIONS Al-Al 2 O 3 nanocomposites with composition of 1, 5, 7 vol. % alumina and microcomposite with 5 vol. % alumina were fabricated successfully by spark plasma sintering method. The distribution profile of alumina particles in the aluminium matrix is better in case of nanocomposites than in the microcomposite. T The interface of aluminium and alumina in nanocomposites is seemingly sound than in the case of microcomposite i.e. the bonding of alumina to aluminum in nanocomposites is proficient but in the case of microcomposite is discontinuous and random. The density of microcomposite is higher than the nanocomposites, but the microhardness of nanocomposites is higher than the mcirocomposite. The nanohardness also shows higher values for nanocomposites than the mcirocomposite. it Themodulus dl of elasticity itvalues of nanocomposites is higherh than that of microcomposite. The TEM SEM and AFM micrographs reveal a lack of intimate proximity in the case of microcomposite than in the nanocomposites.

20 REFERENCES 1. S. Choi, H. Awaji, Nanocomposites-a new material design concept, Sci. Technol. Adv. Mater. 6 (2005) Y. Li, Y.H. Zhao, V. Ortalan, W. Liu, Z.H. Zhang, R.G. Vogt, N.D. Browning, E.J. Lavernia, J.M. Schoenung, Investigation of Aluminum-based Nanocomposites with Ultra-High Strength, Mat. Sci. Eng. A 527 (2009) S.C. Tjong, Z.Y. Ma, Microstructural and mechanical characteristics of in situ metal matrix composites, Mat. Sci. Eng. 29 (2000) S. Vaucher, O. Beffort, Bonding and interface formation in metal matrix composites (MMC), MMC-Assess Thematic Network, EMPA-Thun, volume M.T. Luke, Microstructural Evolution Of Nickel During Spark Plasma Sintering, Master of Science Thesis in Materials Si Science and Engineering, i Boise State Ui University, i May R. German, Sintering theory and practice, John Wiley and Sons, Inc, New York, G. B. Scaffer, B. J. Hall, S. J. Bonner, S. H. Huo, T. B. Sercombe, The effect of atmosphere and the role of pore filling on the sintering of aluminium, Acta Mater. 54 (2006) M. Rahimian, N. Parvin, N. Ehsani, Investigation of particle size and amount of alumina on microstructure and mechanical properties of Al matrix composite made by powder metallurgy, Mat. Sci. Eng. A 527 (2010) Z. Razavi Hesabi, A. Simchi, S.M. Seyed Reihani, Structural evolution during mechanical milling of nanometric and micrometric Al 2 O 3 reinforced Al matrix composites. Mat. Sci. Eng. A 428 (2006) S.S. S Razavi-tousi, R. Yazdani-Rad, S.A. Manafi, Effect of volume fraction and particle size of alumina reinforcement on compaction and densification behavior of Al-Al 2 O 3 nanocomposites, Mat. Sci. Eng. A 528 (2011) Z.A. Munir and Dat V. Quach, Electric Current Activation of Sintering: A Review of the Pulsed Electric Current Sintering Process, J. Am. Ceram. Soc. 94 (2011) 1 19.

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