Study Of Melt Mixing On Microstructures And Properties Of Al-Si Binary Alloy

Hypereutectic Al-Si alloy was strengthened because it has the primary silicon phase in the solidifyingstructure,but because of the primary silicon is normally thick plate to damage plasticity. Strength andhardness of the hypoeutectic Al-Si alloy is lower than the hypereutectic Al-Si alloys, but the plasticity andtoughness is better than that of hypereutectic Al-Si alloys. If can be obtain both hypereutectic structure andhypoeutectic structure in the same Al-Si alloy, it will brings great convenience to the applications of thematerials.In this thesis, through mixing semisolid hypereutectic Al-Si alloy and liquid hypoeutectic Al-Si alloymelt. At the same time get hypereutectic structure and hypoeutectic structure in the same alloy arediscussed. The experimental results show that the melt mixing method used in this paper can at the sametime get the hypereutectic and hypoeutectic composite microstructure. This method is able to refine theprimary silicon phase. Preparation of the alloy in this way has the toughness relatively conventionalhypereutectic alloy was improved, strength and hardness of relatively conventional hypoeutectic alloy wasimproved.By changing the melt temperature and quality, the changes of solidified structure are discussed.Experimental results show that the hypoeutectic Al-Si alloy melt the higher the temperature, the more theamount of the dissolved silicon, the smaller the size of primary silicon.By changing the melt pouring way, the changes of solidified structure was discussed. Theexperimental results show that mix hypoeutectic Al-Si alloy and semi-solid hypereutectic Al-Si alloythrough the method of porous pouring, in the same conditions of temperature and melt quality, couldimprove the adhesion phenomenon of primary silicon.Through adding the metamorphic agent at different stages, influence of metamorphic agent and mixedmethods on solidified structure were discussed. The experimental results show that adding metamorphicagent after the melt blending, Primary silicon refining effect is better than no adding metamorphic agent,distribution is more uniform. hypoeutectic Al-Si alloy melt had added metamorphic agent（NaF+NaCl），hypereutectic Al-Si alloy had added metamorphic agen（tP+S+Al+KCl), two melts was mixed. The primarysilicon and eutectic silicon were refined.