Synthesis of Al/SiC nanocomposite and evaluation of its mechanical properties using pulse echo overlap method

In the present study, pulse echo overlap method (PEO) has been used as a non-destructive technique for evaluating the mechanical properties of Al/SiC nanocomposites. The nano-sized AI/SiC powders were prepared by mechanical alloying method. The particle size and microstructures of the milled powders were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) techniques. Al/SiC powders containing different amounts of nano-size SiC particles (0, 5 and 10 vol.\%) were subsequently cold-pressed and sintered to produce bulk composite samples. The polycrystalline bulk modulus K, Young's modulus E, shear modulus G, Poisson ratio upsilon and hardness H of Al/SiC composites are gained by PEO method. The results showed an increase in the hardness value from 3.8 to 6.6 GPa and a decrease in Al crystallite size from 175.6 to 90.8 nm with increasing SiC content. Besides, Young's modulus of Al/10SiC sample was measured to be 97.1 GPa, which is much higher than that for pure Al (72.6 GPa). Poisson's ratio results indicate that its value decreases with increasing the elastic moduli and ultrasonic wave velocities of Al/SiC composites. The Pugh ratio showed the ductility behavior of all Al/SiC samples, while Poisson's ratio showed slightly decrease in the ionic contribution with increasing the volume fraction of SiC nanoparticles in metal matrix composites MMCs. Microstructural analysis revealed that the origin of change in mechanical properties is attributed to the decrease in interparticle spacing and increase in the grain boundary area, which provides more obstacles for dislocation pile up in the adjacent grains. (C) 2012 Elsevier B. V. All rights reserved.