Improvement of Wear-Resistance in Hyper-Eutectic Al-Si Alloy by Surface Concentration of Primary Silicon Using Electromagnetic Force

Though the aluminum alloy containing silicon exhibits high wear-resistance, primary silicon deteriorates mechanical properties such as elongation and tensile strength due to its brittleness.In this paper a new solidification processing of the aluminum alloy which enable to improve wear resistance without deterioration of the mechanical properties, is proposed, The principle of the processing is to make use of the EMF (electromagnetic force) induced by imposing direct electric current and static magnetic field in the alloy. When EMF is imposed in the molten hyper-eutectic Al-Si alloy in which the primary silicon has been crystallized, EMF scarcely acts on primary silicon particles due to its lower electric conductivity in comparison with the molten alloy. Thus, the primary silicon particles are moved to the surface of a product opposite to the direction of the imposed EMF.The validity of the processing was confirmed by the solidified structures obtained with and without EMF. The high wear-resistance and excellent hardness were demonstrated by using the test pieces treated in the new processing.