Effect of Y 2 O 3 and TiC Reinforcement Particles on Intermetallic Formation and Hardness of Al6061 Composites via Mecha
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AMONG all the aluminum alloys, Al6061 alloys are highly corrosion resistant, have excellent formability, and exhibit higher strength to weight ratio.[1–3] They are ideal materials for structural applications in automotive, aircraft, military, and marine industries. Al6061 metal matrix composites (MMCs) reinforced with ceramic particles such as TiC, SiC, Al2O3, Y2O3, AlN, Si3N4, TiB2, and MoSi2 have been particularly attractive due to possessing superior properties, including high strength at elevated temperature, good fatigue performance, high stiffness, and excellent wear resistance.[4–9] It is important to understand the influence of the reinforcing phases on the mechanical behavior and microstructural evolution of the aluminum-based composites. In earlier work,[10,11] it has been reported that the presence of nanoparticles enhances strength by interacting with dislocations, while simultaneously retarding grain growth. The nanoscale size of the reinforcing particles is also an important factor in determining the plasticity of the materials.[10] Mechanical alloying is a solid-state powder processing technique and can achieve a homogeneous distribution of reinforcement particles throughout the matrix. This technique includes two essential processes, cold welding and the fracturing of powder particles. During highenergy ball milling, processing of the constituent powder CHUN-LIANG CHEN, Associate Professor, and CHEN-HAN LIN, Master Student, are with the Department of Materials Science and Engineering, National Dong Hwa University, No. 1, Sec. 2, Da Hsueh Rd., Shoufeng, Hualien 97401, Taiwan ROC. Contact e-mail: [email protected] Manuscript submitted November 20, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A
particles involves repeated cold welding, fracturing, and rewelding. This enables a variety of materials and alloys to be produced, for example, amorphous, nanostructured materials and MMCs.[12,13] However, mechanical alloying is a complex process and hence optimization of variables is important to achieve the desired product. As a result, much research has been undertaken in recent years to investigate the effect of mechanical alloying conditions on the microstructure evolution and material properties such as mill speed, milling atmosphere, the process control agent, ball to powder weight ratio, and the grinding media.[14–16] In this study, Al6061 reinforced with Y2O3 and TiC particles, fabricated by mechanical alloying, has been investigated. Although there are some studies on the synthesis, consolidation, and mechanical behavior of these types of composite materials,[17–21] there is only a limited amount of research work reporting the effect of reinforcement particles on microstructural changes and mechanical properties of Al6061 composites during the mechanical alloying process. The purpose of the present work is to investigate the formation of intermetallic compounds and complex oxide dispersoids associated with reinforcement particles/matrix interaction of the Al6061 composites. Nanoindent
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