Al-Sc合金相结构的第一原理研究

FIRST-PRINCIPLES STUDY OF THE PHASE STRACTURES OF Al-Sc ALLOYS

采用第一原理赝势平面波方法计算了Al-Sc合金固溶体、有序相和无序相结构对应的形成焓.在无序合金的电子结构研究中,引入了可以描述无序合金结构环境的小尺寸超单胞模型——SQS模型.计算结果表明:超饱和固溶体中的Sc原子具有偏聚产生L1_2结构的Al_3Sc析出相和L1_0结构的AlSc析出相的趋势.依据对各相的电子结构及电子密度分析结果,初步探讨了时效处理导致超饱和固溶体Al(Sc)中偏聚产生L1_2结构Al_3Sc析出相的形成机理.

The formation enthalpies of the Al-Sc compounds and the Al-rich solid solution phase have been studied from first-principles based on plane-wave pseudopotential method.To calculate the electronic structure of the disordered Al-Sc alloys,the small-size special quasirandom structures（SQS）, which exhibited similar structure environments as that of the disordered Al-Sc alloys,are employed. It is shown that the Sc atoms in supersaturated solid solution tend to segregation forming ordered Al_3Sc（L1_2） and AlSc（L1-0） precipitations.The nucleation mechanism of Al_3Sc precipitation phase in the supersaturated Al（Sc） solid solution is analyzed in terms of the calculated densities of states and distributions of electron densities.