固溶处理中Mg-9Gd-2Er-0.4Zr合金的组织演变

摘要

Microstructure evolution of the cast Mg-9Gd-2Er-0.4Zr alloy during solid solution treatment at temperature of 460-520 ℃ for 3-12 h was investigated by using optical microscope (OM),scanning electron microscope (SEM) and transmission electron microscope (TEM).The results indicated that the grain size and the shape of second phase were obviously changed with time and/or temperature going on.At 460 ℃ for 3 h,the morphology of the Mg5(GdEr) phase was changed into fragmentized island morphology and the volume faction of the phase decreased.After solution solid treatment at 460 ℃ for 6 h,the Mgs(GdEr) phase was already completely dissolved,but some cuboid-shaped RE-rich phase precipitated.As the temperature increased,the morphology of the Mg5(GdEr) phase was transformed into the same morphology as that at 460 ℃ for 6 h.It was suggested that the microstructure evolution of the alloy during the solid solution treatment was concluded as follows:Mgs(GdEr) eutectic phase→Gd/Er atom diffusing into matrix→spheroidic Mg5(GdEr) phase→cuboid-shaped RE-rich phase→grain boundary immigration.%利用OM、SEM和TEM研究了固溶处理过程中Mg-9Gd-2Er-0.4Zr铸造镁合金的微观组织演变,其固溶处理温度和时间范围分别为460～520℃和3～12h.结果表明,随着固溶时间的延长和(或)温度的升高,合金的晶粒尺寸和第二相形态均有显著变化.当固溶温度和时间分别为460℃和3h时,Mg5(GdEr)相的体积分数降低并转变为破碎的岛状.当固溶温度和时间分别为460℃和6h时,Mg5(GdEr)相已经完全溶解,但是析出了少量的立方状富RE相.随着固溶温度的升高,Mg5(GdEr)相的形貌演变与固溶温度460℃和时间6h时的相似.在固溶处理过程中合金的组织演变为:Mg5(GdEr)共晶相→Gd/Er原子向基体扩散→类球形Mg5(GdEr)相→立方状富RE相→晶界迁移.