采用金相法和扫描电镜研究了稀土元素在LD31RCS铝型材合金中的分布、存在状态及其对合金金相组织和性能的影响。结果表明,适量稀土主要富集在晶界上,它使合金组织细化,强度、硬度及挤压速度明显提高。过量稀土会形成Al-Si-Fe-RF多元球团状质点,促进韧窝的形核和发展,但它使合金组织粗化,强度和硬度下降。对掺法生产RE-LD31合金的稀土含量以0.2wt％为宜。 The distribution, existing state of rare earth elements in the LD31RCS aluminum alloy and its effect on the microstructure and properties of the alloy were studied by metallographic method and scanning electron microscope. The results show that the proper amount of rare earth is mainly concentrated on the grain boundary, which makes the alloy structure refinement, and the strength, hardness and extrusion speed increase obviously. Excessive rare earth will form Al-Si-Fe-RF multiple pellet-like particles to promote the dimple nucleation and development, but it makes the alloy coarsening, strength and hardness decreased. The rare earth content of RE-LD31 alloy doped with admixture is preferably 0.2wt%.