中文摘要：

镁合金AZ91D中加入质量分数为1％的La时，合金在常温下的抗拉强度和延伸率分别增大了21％和101．2％，并且腐蚀速率下降为原AZ91D的47．2％．其中力学性能的提高主要是由于加入La后形成了（Al，Mg）11La3强化相，同时，细化了β相．耐蚀性的提高则是由于La的加入形成了具有类网状结构的β相，这种类网状结构的β相能有效地抑制腐蚀过程的进行，从而提高了镁合金的耐蚀性．当La加入量进一步增大时，合金力学性能缓慢增大，但其耐蚀性却明显降低，特别是当La达到2％时，合金的腐蚀速率甚至高于原合金的腐蚀速率．这主要是由于过多的La导致镁合金基体α相的Al含量大大降低，从而降低了镁合金的耐蚀性．

英文摘要：

The microstructure, mechanical property and corrosion behavior of AZ91D with addition of lanthanum were investigated. When adding 1% lanthanum, the ultimate tensile strength and the elongation increased by 21.1% and 101.2%, respectively, which resulted from the refinement of the β phase and the formation of （Al, Mg）11La3 strengthening phase, while the corrosion rate decreased to 47.2%. But when La content was over 1%, the corrosion rate increased. Small amount of La addition could form the small β phase grains similar to net-like structure, which could restrain the corrosion at some extent. Large amount of La addition caused the depletion of Al in α matrix, which increased the corrosion rate.