挤压铸造对Al-Cu合金显微组织及溶质分布的影响

研究了挤压铸造工艺条件下,工艺参数对Al-5Cu-0.4Mn合金显微组织及Cu元素分布的影响。结果表明,合金在25MPa压力下成形时,初生α-Al晶粒尺寸得到明显细化;浇注温度越高组织变得越粗大;升高模具预热温度,晶粒尺寸增大且分布不均匀。挤压铸造改变重力铸造条件下Cu的逆偏析现象,从铸件边缘往心部的Cu含量呈现增加的趋势,主要原因为晶间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内侧。Cu在α-Al基体中的固溶度随着压力的增大而增加;沿径向远离铸件心部,α-Al晶内Cu含量逐渐增加。在挤压力为100MPa、浇注温度为680～730℃、模具温度为200℃的工艺条件下,可获得晶粒细小、组织致密、宏观偏析少的Al-5Cu-0.4Mn合金挤压铸件。

Effects of Squeeze Casting on Microstructure and Solute Distribution in Al-Cu Alloy

Effects of processing parameters on microstructure and Cu distribution in squeeze casting Al-5Cu-0.4Mn alloy were investigated.The results show that primary α-Al grain size in the alloy is significantly refined with solidification under a pressure of 25 MPa.Coarse microstructure is increased with increasing in pouring temperature.Non-uniform and coarse microstructure is formed with increasing in mould preheating temperature.Normal solute concentration profile can be observed in the squeeze casting alloy rather than inverse segregation under gravity casting Cu content is increased from the edge to the center.That is attributed to solute-rich driven to the inside of the castings through skeleton channel of inter-dendrite by forced feeding of pressure.The average solubility of Cu in α-Al matrix is increased with the increase of applied pressure.Cu content in primary α-Al grain rises with radius distance of the specimen.Sound squeeze castings of Al-5Cu-0.4Mn alloy with fine grain structure and less macro-segregation can be obtained with a pressure of 100MPa,pouring temperature of 680～730 ℃,and die temperature of 200 ℃.