Electromagnetic Stir Casting: An Approach to Produce Hybrid Metal Matrix Composite (MMC)

(Figure: Experimental Setup)

A metal matrix composite is a composite material that constitutes one metal and other different metal or another material like ceramic or organic compound. When at least three materials are present it constitutes hybrid MMC. The use of composite increases day by day in defense, automobile, aviation, aerospace industry. Now a day’s hybrid MMC development and characterization play an important role in the industry. Hybrid aluminium MMC has better mechanical properties like hardness, tensile strength, impact strength, microstructural morphology etc. and good tribological properties.

The metal matrix materials for hybrid MMC are aluminum, copper, magnesium, titanium alloys while the reinforcement can be widely used Al2O3, SiC, BN, B4C, B, AlN, TiB2, graphite etc. Electromagnetic stir casting method is an effective way to produce hybrid metal matrix composites. Electromagnetic fields are often used industrially to control the flow of liquid metal. An alternating field induces eddy currents in liquid metal which interact with the field to give a Lorentz body force which is generally rotational and which must, therefore, drive fluid motion.

In the high-frequency limit, the field is confined to a narrow layer on the surface of the conductor. Electromagnetic stirring uses the principle of a 3 phases induction motor and it differs from the conventional mechanical stirrer as it is a non-contact type stirrer in which no part is in contact with the molten metal. The molten metal is mixed with the material by electromagnetic action.

Electromagnetic stirring has the advantage of having no contact between the melt and the stirring system. To achieve the optimum properties of the hybrid MMC, the distribution of the reinforcement material in the matrix alloy should be uniform, and the wettability between these substances should be optimum. This method is having an edge over other MMC fabrication methods due to the more uniform distribution of reinforced particles. Hybrid composite applications continue to expand, the spectrum of materials and processes employed will remain relatively wide.