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AZ91D合金中加入1%La(质量分数)后,不但形成了条状的Al_(11)La_3相和块状的Al_8LaMn_4相,而且在粗大β相(Mg_(17)Al_(12))周围形成了许多细小的层片状β相,并使β相进一步网状化.这些细小的层片状β相明显阻碍了腐蚀的扩展,提高了AZ91D镁合金的耐蚀性.条状的Al_(11)La_3相和块状的Al_8LaMn_4相都属于阴极耐蚀相.其中Al_(11)La_3相由于较小的阴极面积,对加速其周围镁基体的腐蚀不起明显作用;而块状的Al_8LaMn_4相阴极面积较大,与基体构成微电偶腐蚀,加速了基体的腐蚀.
The addition of 1% La (superscript 2 +) to AZ91D alloy not only formed the Al 11 La 3 phase and the massive Al 8 LaMn 4 phase, but also formed around the coarse β phase (Mg 17 Al 12) Many fine lamellar β phases and further β lamellar reticulation.These tiny lamellar β phases obviously obstruct the corrosion growth and improve the corrosion resistance of AZ91D magnesium alloy.The stripe Al 11 La_3 phase and bulk Al_8LaMn_4 phase belong to the cathodic corrosion resistant phase, in which the Al_ (11) La_3 phase does not play a significant role in accelerating the corrosion of the surrounding magnesium matrix due to the smaller cathode area; while the bulk Al_8LaMn_4 phase cathode area Larger, with the substrate form micro galvanic corrosion, accelerated corrosion of the substrate.