Delivered by Publishing Technology to: Chinese University of Hong Kong IP: 117.253.226.93 On: Mon, 14 Mar 2016 06:57:45 Copyright: American Scientific Publishers Copyright © 2010 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 10, 956–964, 2010 Simultaneous Enhancement of Tensile/Compressive Strength and Ductility of Magnesium Alloy AZ31 Using Carbon Nanotubes M. Paramsothy 1 , S. F. Hassan 2 , N. Srikanth 3 , and M. Gupta 1 ∗ 1 Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576 2 Department of Mechanical Engineering, King Fahd University of Petroleum & Minerals, P.O. Box No. 1061, Dhahran 31261, Kingdom of Saudi Arabia 3 Centre for Management of Science and Technology, Department of Industrial & Systems Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 117574 AZ31 nanocomposite containing carbon nanotube (CNT) reinforcement was fabricated using solid- ification processing followed by hot extrusion. The CNT reinforcement was integrated with AZ31 using an Al foil method. The AZ31 nanocomposite exhibited slightly smaller grain and intermetallic particle sizes than monolithic AZ31, reasonable CNT distribution, dominant (1 0 -1 1) texture in the transverse and longitudinal directions unlike monolithic AZ31, and 48% higher hardness than mono- lithic AZ31. Compared to monolithic AZ31, the AZ31 nanocomposite exhibited higher 0.2%TYS, UTS, tensile failure strain and tensile work of fracture (WOF) (+10%, +17%, +68% and +92%, respectively). Similarly, compared to monolithic AZ31, the AZ31 nanocomposite exhibited higher 0.2%CYS, UCS, average compressive failure strain and compressive WOF (+58%, +3%, +5% and +17%, respectively). Inclusive of crystallographic texture changes, the effect of CNT integration on the enhancement of tensile and compressive properties of AZ31 is investigated in this paper. Keywords: AZ31, CNT, Nanocomposite, Texture, Mechanical Properties. 1. INTRODUCTION Magnesium and aluminium are commonly used light met- als in the automotive and aerospace weight-critical struc- tural applications. Mg is about 35% lighter than Al. Both metals have similar melting points and strengths. Mg has the disadvantage of limited ductility attributed to its HCP structure, while Al is more ductile given its FCC struc- ture. The elastic modulus of Mg is also lower (40–45 GPa) compared to Al (69.6 GPa). 1 Traditional alloying can be used to increase strength and ductility of Mg. 2 Addi- tionally, many properties of Mg have been improved beyond the limits of alloying with the use of discontinuous reinforcement. 3 In recent years, three methods that have been tried to improve the strength, ductility and modulus of Mg are: (a) use of various oxide nanoparticles as well as CNTs for improving strength and ductility, 4–6 (b) use of metallic particles such as Ti and Mo for improving ductility 7–9 and (c) use of micron size ceramic particulates for improving strength and modulus. 10 11 AZ31 is a very ∗ Author to whom correspondence should be addressed. commonly used Al-containing (or Zr-free) Mg alloy in the world today, and is characterized by: (a) low cost, (b) ease of handling, (c) good strength and ductility and (d) resis- tance to atmospheric corrosion. Recently, AZ31 has been surface-reinforced using the friction stir processing tech- nique with SiC microparticulates, 12 C 60 molecules, 13 and multi-walled carbon nanotubes. 14 Good dispersion and hardening of the base matrix were reported in these stud- ies. Similar findings along with grain refinement were also reported for AZ31 reinforced with SiC and B 4 C micropar- ticulates using gas-tungsten arc (GTA) with simultaneous reinforcement powder feeding processing technique. 15–17 Defect-free and adherent particle-matrix interface has been reported in the AZ31/SiC microcomposite. 16 17 Using pulsed current hot pressing (PCHP), TiNi shape memory alloy (SMA) fibers have been incorporated in AZ31 matrix without significant interfacial reaction. 18 As a consequence of residual compressive stress in the AZ31 matrix due to phase change induced shrinkage of the TiNi fiber, the yield stress and elongation in the AZ31/TiNi microcom- posite increased with temperature (strength significantly exceeded that of AZ31 matrix). Researchers added Al 2 O 3 956 J. Nanosci. Nanotechnol. 2010, Vol. 10, No. 2 1533-4880/2010/10/956/009 doi:10.1166/jnn.2010.1809