中文摘要：

用光学显微镜、扫描电镜、EDS能谱仪等手段，研究了镧对ADC12铝合金固溶时效显微组织、固溶温度条件对ADC12稀土铝合金显微组织的影响。结果表明，加入镧后，固溶时效组织中粗大的块状多边形初晶硅消失；针状的共晶硅形貌得到改善，由长针状变为短棒状，并且得到不同程度的细化和球化，且弥散分布；同时加入镧后有害化合物形态得到改善，且固溶温度越高，有害金属间化合物溶解越多，晶粒越细小；镧质量分数为0．3％，硅相细化、球化效果较佳，过量的镧会生成大量的黑色针状金属间化合物。

英文摘要：

The effects of lanthanum on microstructure of ADC12 aluminum alloy solid solution and aging treatment were studied by means of optical microscopy （OM）, scanning electron microscope （SEM） and energy diffraction spectrum （EDS）. At the same time, the effect of solid solution temperature on microstructure of ADC12 aluminum alloy was researched. The re- sults show that after adding La, the coarse block - like polygonal primary silicon disappeared in the solution and aging micro- structure. The acicular eutectic silicon morphology was transformed from long acicular - like to the short stick - like. It gets remarkably refined, spheroidized and homogeneous distribution. Besides, the morphology of harmful compounds is improved, and the harmful intermetallic compounds are dissolved more and the grains are smaller when the alloy is solution treated at higher temperature. The effect of grain refinement and spheroidization on silicon phase is the best when the mass fraction of lanthanum is 0.3%. However, it will form a large number of black acicular - like intermetallic compounds after adding excessive La.