Study On Interfacial Microstructure And Properties Of (A356_?l?/T2_?s?) Bimetal In Liquid-solid Compound Casting Process

With the progress of science and technology,the single metallic material could not satisfy the needs for industrial production.In this case,it is necessary to develop composite materials with superior property.Al/Cu bimetallic composite material,combing the excellent properties of both aluminum and copper,exhibits not only light and cheap but also outstanding electrical and thermal conductivity.Therefore,Al/Cu bimetallic composite material has been widely applied in some fields such as electricity industry,automotive industry,metallurgical engineering and so on.In this paper,liquid-solid composite casting method was adopted for the preparation of Al/Cu bimetallic composite material.Subsequently,based on the analysis of the microstructure and properties of the composite,we improved the bonding strength and electrical conductivity of the Al/Cu joint via adjusting the preheating temperature,preheating time and adding element Ce/Sr.The results obtained could provide a method of guidance for its application in manufacturing.The fabrication of Al/Cu bimetallic composite material was carried out on a home-made equipment for vacuum liquid-solid compound casting.Among the three different layer formed in Al/Cu joint,we focus on the analysis of the intermetallic layer,which are Al2Cu(?)?AlCu(?2)?Al3Cu4(?2)?Al2Cu3(?)?Al4Cu9(?1),respectively.Because thick intermetallic layer can exert some negative effect on the bonding strength and electrical conductivity of the Al/Cu joint,it needs to optimize the parameters of Al-Cu liquid-solid compound casting.We found that less intermetallic compounds and thinner intermetallic layer appeared with lower preheating temperature and shorter preheating time.Moreover,the bonding strength and electrical conductivity of the Al/Cu joint can be improved remarkable.However,some gaps and voids appeared in the Al/Cu joint,resulting from too low preheating temperature and too short preheating time,which leads to worse bonding strength and electrical conductivity.Based on the results with shear strength 42.5Mpa and the electrical conductivity 39.3MS/m,the optimized preheating temperature and preheating time can be 750? and 1 min,respectively.Besides,we explored the influence of Ce/Sr on the microstructure and properties of Al/Cu bimetallic composite material under the optimized parameter mentioned before.It can be concluded that Ce could not improve the microstructure and electrical conductivity of the Al/Cu joint effectively.On the contrary,the addition of Sr can result in the transition of the morphology of eutectic silicon from coarse plate-like or acicular to fine fibrous and dot-like spherical shape.Ideally,the ?-Al phase was refined and the electrical conductivity of the Al/Cu joint added up to 44.6MS/m.As supplementary,the theory of Ce/Sr modification and the principle of electrical conductivity improvement was discussed thoroughly.