【作者】 上官玉辉；

【导师】 王杰芳；

【作者基本信息】 郑州大学 ， 凝聚态物理， 2010， 硕士

【摘要】 本文以不同Cu含量Al-Cu合金为研究对象,研究了不同Ti含量对亚共晶Al-5wt.%Cu合金的微观组织细化,对比研究了常规铸造条件下和不同冷却速度下不同Cu含量Al-Cu合金的微观组织,通过DSC分析了冷却速度对不同Cu含量Al-Cu合金熔化潜热的影响。研究结果包括以下几个方面：(1)不同的Ti含量对亚共晶Al-5wt.%Cu合金的微观组织晶粒细化：随着Ti含量的逐渐增大,晶粒尺寸变小。当Ti含量为0.1wt.%时晶粒尺寸最小。当Ti含量大于0.1wt.%以后,晶粒细化效果呈下降趋势。(2)不同Cu含量Al-Cu合金微观组织对比：亚共晶Al-Cu合金中,随着Cu含量的增加,初生α-Al相所占比例逐渐减小,共晶组织所占比例增加；共晶Al-Cu合金是共晶组织(a-Al相+0-Al2Cu相),呈片层状分布。(3)冷却速度对过共晶Al-40wt.%Cu合金微观组织的影响：随着冷却速度的增大,初生θ-Al2Cu相由方块状变得更加细小,晶粒尺寸由45μm左右减小到10μm左右。其主要原因是冷却速度增大时,会造成合金内部的过冷度增大,抑制了初生θ-Al2Cu相的析出和长大。从冷却速度和晶粒尺寸标准差的关系图看出,要想获得晶粒尺寸分布均匀性好的材料,需要提高合金的冷却速度。(4)通过对不同Cu含量Al-Cu合金DSC曲线的观察分析得出：常规铸造条件下,亚共晶Al-Cu合金中,随着Cu含量的增加,共晶组织比例增加,其熔化对应的峰值温度在升高。在含Cu量为5wt.%-40wt.%的范围内,随着Cu含量的增加,Al-Cu合金的熔化潜热逐渐减小。(5)距楔形试样尖端1cm处,冷却速度较大,亚共晶以及共晶Al-Cu合金的DSC曲线中初生α-Al相和共晶组织所对应的熔化吸热峰的温度逐渐增大,相同Cu含量Al-Cu合金的熔化潜热比常规铸造条件下减小。(6)随着冷却速度逐渐增大,亚共晶Al-20wt.%Cu合金的熔化开始温度、低温吸热峰、高温吸热峰、熔化终止温度逐渐增大,合金的熔化潜热逐渐减小。(7)随着冷却速度的增大,亚共晶Al-20wt.%Cu合金的硬度逐渐增大,过共晶Al-40wt.%Cu合金的硬度反而逐渐减小。更多还原

【Abstract】 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.更多还原