| 4004 aluminum alloy is used as the 434 compound aluminum foils due to thelow melting point, good wetting and good fluidity. At the certain temperature,4004 aluminum alloy can be used as the brazing material. During the producingprocess of 4004 alloy ingots, because of a higher content of silicon element, thesilicon phase presents the coarse lamellar or needle-like morphology. Therefore,the matrix of aluminum alloy is split and the mechanical properties are worsened,especially the plasticity, which directly results in the defect formation duringrolling. In this paper, the influences of modification of 4004 aluminum alloymodified by Sr, RE, and Sr-RE are investigated.Firstly, by comparison tests, the influences of additions, holding time of theSr and RE on the microstructure and properties of 4004 aluminum alloy areanalyzed. Experimental results show that additions of Sr and RE have apronounced effect on the microstructure of alloy: primary and eutectic structuresare apparently refined. When the content of Sr reaches to 0.04wt.%, themodification effect is the best: elongation of 4.4% and tensile strength of 199MPa.When the content of RE reaches to 0.2wt.%, the modification effect is the best:elongation of 4.3% and tensile strength of 201MPa. The best holding time for Srand RE is 60min.Secondly, by orthogonal experimental design, the best modification situationfor Sr-RE is: 0.03%Sr, 0.15%RE, 740℃, 60min.Thirdly, when the content of RE is fixed at 0.15wt.%, the temperature ofmodification 740℃, the holding time 60min,the influence of the content Sr onthe interactive compound modification is investigated. When the contend of Sr is0.03wt.%,α-Al is obviously refined and the eutectic silicon looks like fibrous. At the same time, mechanical properties reach the highest point: the elongation of5.8% and tensile strength of 252MPa. When the holding time is within 90min, alloy would not occur over deterioration phenomenon.Finally, the influence of T6 heat treatment on the microstructure ofcompounded-modified alloy by Sr-RE is researched. The results show that heattreatment has a significant effect on microstructure and mechanical properties ofthe alloy. The morphologies of refined eutectic structure are in the oval-shape orround-shape, and are evenly distributed inα-Al. The elongation reaches to 6.6% and tensile strength to 268MPa.
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