对加入不同量稀土元素镧的A356.2铸造铝合金的显微组织进行了分析,研究了稀土元素镧加入量对合金显微组织的影响。结果表明：合金的基体显微组织主要由α-Al相和共晶硅相组成，当稀土元素镧加入量大于0.4%(质量分数)时，合金显微组织中开始有较大颗粒状的稀土元素镧相析出，且析出量随稀土元素镧加入量的增加而增加；稀土元素镧对合金显微组织中的α-Al相有细化作用，随着稀土元素镧加入量的增加，合金显微组织中的共晶硅相由针片状逐渐变为块状和颗粒状以及细小的颗粒状。

The microstructure of A356.2 cast aluminum alloy with different contents of rare earth element lanthanum was analyzed, and the effects of adding amount of lanthanum on microstructure of the alloy were studied. The results show that the matrix microstructure of the alloy was mainly composed of α-Al phase and eutectic silicon phase. When the adding amount of rare earth element lanthanum was more than 0.4% (mass fraction), large rare earth element lanthanum phase particles began to precipitate in microstructure of the alloy, and the precipitation amount increased with the increase of adding amount of lanthanum. The rare earth element lanthanum could refine the α-Al phase in the microstructure, and with the increase of adding amount of lanthanum, the eutectic silicon phase in the microstructure gradually changed from needle-like shape to massive and granular shape and then to fine granular shape.