The Base Study Of Al-alloy Electromagnetic Rheocasting

The problems of lightening motorcar and recycle of material were brought forward for sparing energy sources and protecting environment of the Earth. The electromagnetic semi-solid casting is appreciated in the field of motorcar since it is the effective way of improving performance of Al-alloy accessory and lightening casting weight.In this paper, the electromagnetic stirring device was manufactured according to the demands, and the characters of melt, the structure of AI-24%Si hypereutectic alloy and the effect of various parameters on the structure of Al-6.6%Si hypoeutectic were investigated for providing theory direction in the field of industry production and improving its application further. The results indicated: the particles of α -Al phase that were non-existent through non-stirring casting in AI-24%Si hypereutectic alloy appeared through electromagnetic agitation and the primary silicon with cluster distributed on the matrix of alloy when the cooling rate was 10℃/min and the primary silicon with dot distributed on the matrix of alloy and the particles of α -Al phase became small when the cooling rate was 60℃/min; the α -Al phase of dendritic structure appeared firstly during solidification of the Al-6.6%Si hypoeutectic alloy under the electromagnetic agitation, the rupture of dendritic taked place under the mix convection mechanism and the dendritic firstly appeared was incurvated at roots under stirring force, which led to the dislocations occurring at the roots of dendritic, the dislocations getting together, incorporating and stuffing up and necking at the roots; the electromagnetic force and dislocations and heating undulation provided the root with enough energy, which led to the dendritic rupturing rapidly at the roots; the particles of non-dendritic α-Al phase were little with increasing the stirring intensity and decreasing the cooling rate; the particles of α -Al phase were incorporated rapidly and the number of α -Al phase particles in the unit volume greatly decreased when the temperature of AI-6.6%Si hypoeutectic alloy melt reduced to about 620℃.At last, the mechanical properties of alloy under different conditions of casting were investigated. The results indicated: the hardness , plasticity and intensity of Al-24%Si hypereutectic alloy and Al-6.6%Si hypoeutectic alloy under electromagnetic stirring were both greatly improved comparing with non-stirring casting.