基于田口方法的挤压铸造Al5Cu0.4Mn合金宏观偏析

摘要

采用田口方法分析挤压铸造参数对Al5Cu0.4Mn合金中Cu宏观偏析的影响规律,并预测在优化的挤压铸造参数条件下Cu的偏析程度.结果表明:挤压铸造参数对Cu宏观偏析影响由大到小依次为浇注温度、模具温度、挤压力和挤压前延迟时间；在680℃浇注温度、200℃模具温度和75MPa挤压力下,能得到宏观偏析较小的铸件.经扫描电镜和金相分析:挤压铸造易造成Cu的正偏析,主要因为固液界面前沿处富铜液相在压力的强制补缩下,通过枝晶骨架通道被挤向铸件心部,而并非重力铸造下的逆偏析现象;且在挤压铸件内形成平行于模壁的长条鱼骨状共晶偏析带,这种偏析带从铸件表面往心部逐渐减少.%Taguchi method was used to investigate the effects of applied pressure(p), pouring temperature(Tp), die temperature(Td) and delay time(td) on the macrosegregation of Cu in the squeeze casting of A15Cu0.4Mn alloy. And the level of macrosegregation in cast ingot under optimized conditions was predicted successfully. The results show that the influence sequence of squeeze casting parameters on macrosegregation from large to small is Tp, Td, p, td. The pouring temperature of 680 ℃, die temperature of 200 ℃ and applied pressure of 75 MPa were proposed for obtaining the sound squeeze castings. Through analysis of composition and microstructure by SEM and OM, it is revealed that the squeeze casting leads to the normal segregation of Cu rather than inverse solute concentration profiles under gravity casting conditions. It is the action of applied pressure that resulted the filling of shrinkage porosity with backflow of solute-rich liquid along the interdendritic channels. And fish-bone-like segregation strips form, which are parallel to the die wall. The amount of segregation strips decreases from edge to center in the cast ingot.