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 Mg5（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：Mg5（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。
基金
Projects(2011BAE22B01,2011BAE22B04-2) supported by the National Key Technology R&D Program during the 12th Five-Year Period
Projects(51071004,51101002) supported by the National Natural Science Foundation of China
