Metal matrix nanocomposites (MMNCs) with the addition of nano-sized ceramic particles can be of significance for automobile, aerospace and numerous other applications. The physical and mechanical characteristics of the light refractory carbides such as SiC, TiC and B 4 C make them suitable for being used as reinforcement in aluminium base metal matrix composites This paper presents a technique for an inexpensive fabrication of bulk lightweight MMNCs with reproducible microstructures and superior properties by use of ultrasonic nonlinear effects, namely transient cavitation and acoustic streaming; to achieve uniform dispersion of nano-sized B 4 C particles in molten aluminum alloy. Nano-sized B 4 C p enhanced properties of aluminium matrix composites, with 1.5%wt of B 4 C. As compared to the base metal alloy, the mechanical properties including tensile strength and yield strength of the nanocomposites were improved significantly, while the ductility of base metal alloy matrix castings was retained. Micro structural study was carried out with an optical microscope and SEM which validates a good dispersion of nano-sized B 4 C p in metal matrix. Mechanical properties of the as-cast MMNCs have been improved significantly even with a low weight fraction of nanosized B 4 C.
Damping is a measure of rate at which vibration energy dissipates in any structure. In order to protect any structure from vibration damping needs to be enhanced. Damping exists in many forms like material damping, dry friction damping, etc. Damping is even influenced by the manufacturing process. Out of two manufacturing types that are casting and forging it is found that casting imparts more damping than forging. The reason for which is attributed to the casting defects like blowholes. But for a casting of given shape, geometry, dimensions and volume allowable number of blow holes for the desired strength are not specified anywhere. The outcome of the paper would be bringing out the relation between number of blowholes and their orientation with respect to strength and damping characteristics in a controlled casting environment.
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