JOURNAL OF COMPOSITE MATERIALS Article Wear and friction behavior of nanosized TiB 2 and TiO 2 particle-reinforced casting A356 aluminum nanocomposites: A comparative study focusing on particle capture in matrix M Karbalaei Akbari 1 , S Rajabi 2 , K Shirvanimoghaddam 3 and HR Baharvandi 4 Abstract In the present study, regarding the theoretical and practical aspects of nanoparticle capture in liquid-state processing of aluminum composite, different volume fractions of TiB 2 and TiO 2 nanopowders were incorporated into aluminum alloy via stir casting method. Hardness and sliding wear test were carried out to evaluate the mechanical properties of composites. The effects of wear load and reinforcement content on wear rate and friction coefficient of composites were examined. Microstructural studied showed that particle distribution in A356-TiB 2 composites was more favorable than that of the A356-TiO 2 samples. Results showed that nanoparticles were partially captured by aluminum matrix. With an increase in reinforcement content the amount of porosity and rejected nanoparticles increased. Regarding the wettability features of particles, the amount of introduced TiB 2 powders was higher than that of TiO 2 particles. A356-TiB 2 composites showed higher mechanical properties compared with those of A356-TiO 2 samples. Significant improvements in hardness and wear resistance were obtained in A356-1.5 vol.% TiB 2 composite. It was observed that the friction coefficient of the composites was lower than that of the non-reinforced alloy. With an increase in normal wear load, wear rate of composites increased and friction coefficient of reinforced samples decreased. Study on surface morphology of the worn surfaces showed both of the mild and sever wear mechanisms. The depth and number of grooves in worn surface of composites decreased with introduction of nanoparticles into matrix. The presence of oxide layers was detected on worn surface. Iron trace was observed in wear debris of samples. Keywords Metal matrix nanocomposites, stir casting, wear, scanning electron microscope Introduction The applications of aluminum alloys are limited because of poor wear resistance at room and elevated temperatures. 1–3 It was reported by several investiga- tors that the incorporation of hard ceramic particles into the aluminum alloys enhanced the wear resistance. Aluminum alloys reinforced with ceramic particles are universally termed as aluminum matrix composites (AMCs). Al–Si alloy-based particulate reinforced metal matrix composites have emerged as an important class of high performance materials for use in aero- space, automobile, chemical, and transportation indus- tries because of their improved strength, stiffness, low 1 Faculty of Metallurgical and Materials Engineering, Semnan University, Iran 2 Department of Materials Science and Engineering, Sharif University of Technology, Iran 3 Institute for Frontier Materials, Deakin University, Australia 4 School of Metallurgy and Materials Engineering, University of Tehran, Iran Corresponding author: M Karbalaei Akbari, Faculty of Metallurgical and Materials Engineering, Semnan University, Semnan Province P.C 35131-19111, Iran. Email: m_akbari@sun.semnan.ac.ir Journal of Composite Materials 0(0) 1–17 ! The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0021998314568327 jcm.sagepub.com by guest on January 23, 2015 jcm.sagepub.com Downloaded from