Effect Of Cooling Rate On The Microstructures And The Latent Heat Of Al-Cu Alloy

Al-Cu alloy with different Cu contents were investigated in this paper. Firstly, the effects of different Ti contents on microstructure refinement of hypoeutectic Al-5wt.%Cu alloy were studied, secondly, microstructures of Al-Cu alloy with different Cu contents were comparative studied in conventional casting conditions and different cooling rates conditions, finally, the effects of cooling rate on the latent heat in Al-Cu alloy with different Cu contents by DSC were analyzed. The results showed that as follows:(1)Grain refinement of microstructures on hypoeutectic Al-5wt.%Cu alloy with different Ti contents:With the increasing of Ti contents, the grain was refined, when the Ti content was 0.1wt.%,the grain size was smallest; when the Ti contents were more than 0.1wt.%,the grain refinement was in downward trend.(2) Microstructures of Al-Cu alloy with different Cu content were in contrast:In hypoeutectic Al-Cu alloy, with the increasing of Cu contents, the primary phaseα-Al percentage decreased, the proportion of eutectic increased;eutectic Al-Cu alloy was the eutectic (a-Al phase+θ-Al2Cu phase), showed laminar distribution.(3) The effects of cooling rate on the microstructures of hypereutectic Al-40wt.%Cu alloy:with the increasing of cooling rate,θ-Al2Cu phase became more refined, the grain size reduced from about 45μm to 10μm. The main reason was that the increasing of cooling rate will cause undercooling increased and restrain the primary phase precipitation and growth. The graph of the relationship between cooling rate and standard deviation of grain size showed that in order to get material with good distribution of grain size, it need to increase the cooling rate of the alloy.(4) The DSC curves of Al-Cu alloy with different Cu content were observed and analyzed:In conventional casting conditions, with the increasing of Cu contents, the proportion of eutectic increased in hypoeutectic Al-Cu alloy,which peak temperature increased.The latent heat of Al-Cu alloy decreased with the increasing of Cu contents raging from 5wt.%to 40wt.%. (5) 1cm from the wedge tip with high cooling rate, the peak temperature of melting endothermic of the DSC curves in hypoeutectic and eutectic Al-Cu alloy increased, the latent heat of Al-Cu alloy with same Cu contents became smaller.(6) With the increasing of cooling rate, the beginning of melting temperature, the low temperature endothermic peak, the high temperature endothermic peak and the ending of melted temperatures of hypoeutectic Al-20wt.%Cu alloy increased, the latent heat decreased.(7) With the increasing of cooling rate, the hardness of hypoeutectic Al-20wt.%Cu alloy increased gradually, but the hardness of hypereutectic Al-40wt.%Cu alloy decreased gradually.