Al-Li-Mg合金电场下自由能的TF方程计算

Calculation of Free Energy of Al-Li-Mg Alloy by TF Equation

基于Thomas-Fermi(TF)模型,确定电场作用下的内势场边界条件,建立了电场作用下单原子、化合物,固溶体、实际工业合金的自由能计算方法,系统地定量计算研究了电场作用下自由能的变化趋势。结果表明:单原子自由能变化趋势在电场作用下是关于非零电场对称的,并且不同元素的自由能对电场的敏感性不同,Al,Mg,Li3元素在正电场一侧的敏感性依次为Al,Li,Mg;在负电场一侧的敏感性依次为Al,Mg,Li。电场作用下Al3Li化合物和固溶体Al-2.14%Li(原子分数,下同)的自由能在460K和800K表现出不同电场对称性和电场敏感性。在两种温度下,Al-2.14%Li固溶体自由能的电场敏感性要高于化合物Al3Li。而且在800K高电场下固溶体Al-2.14%Li的自由能明显高于化合物Al3Li的自由能,在460K相同的电场下,化合物的自由能低于固溶体的自由能。1420合金自由能的变化趋势是关于零电场对称的,时效电场下1420合金的拉伸性能也是关于零电场对称的。

Based on the TF （Thomas-Fermi） equation, the interior potential boundary condition under the electric field was established. Free energies were calculated under the influence of electric field with the defined boundary for the single atom, solid solution, compound and practical alloys. It can be concluded that the monatomic free energy under the electric field was not symmetrical about zero point of the external potential. The free energy sensitivities of the three calculated elements on the side of positive electric field take turns ofAl, Li, and Mg, and take turns of Al, Mg and Li on the side of negative electric field. The free energies of Al3Li compound and Al-2.14%Li solid solution exhibit different electric field symmetries and sensitivities in the electric field, and the Al-2.14%Li is more sensitive than the Al3Li at 460 K and 800 K. The free energy of solid solution Al-2.14%Li is higher than the compound Al3Li at 800 K under higher electric field, the free energy of Al3Li is lower than Al-2.14% Li at 460 K. The free energy of 1420 alloy is symmetrical about the zero external potential, consistent with its tensile properties during aging process in the electric-field.