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Abstract: Ultrasonic degassing has been shown to be a reasonably efficient way of degassing a melt. Similarly, vacuum degassing has also been proven to be beneficial in producing high quality products. However, neither method is sufficiently efficient. Moreover, a combination of these techniques does not respond well to large volumes of melt. In this article, a novel approach, using ultrasonic assisted argon degassing was examined and compared with vacuum and argon degassing. The results indicate that the ultrasonic-argon degassing process is a faster method and can be used for large volumes of melt, thus overcoming the restrictions of the other two methods. [Copyright &y& Elsevier]

The effect of combined electromagnetic–ultrasonic fields evaluated on grain refinement. Cavitation induced by the combination of technologies suggested as major mechanism for grain refinement. A numerical simulation performed predicting the cavitation regions in the molten AA5754 aluminum alloy. It was concluded that the cavitation phenomenon occurs near the electromagnetic and ultrasonic sources. The observed acoustic streaming induced by ultrasonic horn is more intensive than the electromagnetic one. The ultrasonic streaming could transport small bubbles into the bulk rapidly. These micro-bubbles collapsed due to acoustic vibrations where the resulting micro-jets were strong enough to break the oxide layer, wetting impurities. Exogenous particles, intermetallic and oxides may contribute to the formation of fine, uniform and equiaxed microstructure across the treated melt. Experimental results confirmed the simulation predictions. [ABSTRACT FROM AUTHOR]

Abstract: Grain refinement of aluminium alloys has been an established method of improving mechanical properties of aluminium alloys. A5754 wrought aluminium alloy offers a number of attractive superior properties, however, refinement of this alloy and other wrought alloys is still a matter of concern. A novel technique is introduced for the refinement of wrought and cast alloys, using A5754 alloy as a model material. This method not only provides fine and uniform microstructure throughout the products but it also offers possibilities of industrial applications. This technique eliminates the problems associated with chemical grain refinement and introduces physical refinement as a better option for achieving fine grain sizes. [Copyright &y& Elsevier]

Abstract: The application of Melt Conditioner (MC) for production of high-quality DC billets and slabs at semisolid state is examined. In this technique, liquid metal is continuously fed into a twin-screw melt conditioning device, where the liquid metal or semisolid slurry is subjected to high shear rate, and then delivered continuously into a DC caster. In this paper, the feasibility of MCDC of a wrought aluminium alloy in the semi solid state has been investigated and the possibility of DC casting by MC technique below the liquidus temperature as a novel idea was explored. This idea may challenge the conventional DC casting which is normally performed above liquidus temperature. [Copyright &y& Elsevier]