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采用基于密度泛函理论的Castep和Dmol程序软件包,计算了Mg17Al12、Al2Y及Al2Ca相的结构稳定性、弹性性能与电子结构。形成热和结合能计算结果表明:Al2Y具有最强的合金化形成能力和结构稳定性;热力学性质计算结果表明:在298~573 K温度范围内,Al2Y的Gibbs自由能始终最小,其结构热稳定性最好,Al2Ca次之,Mg17Al12最差,Y和Ca合金化Mg-Al系合金形成Al2Y及Al2Ca利于提高镁合金的高温抗蠕变性能;弹性常数的计算结果表明:3种金属间化合物均为脆性相,Mg17Al12的塑性最好;采用弹性常数计算结果预测的Al2Y熔点最高,其结构热稳定性最好。态密度和Mulliken电子占据数的计算结果表明:Al2Y结构最稳定的原因,主要源于体系在Fermi能级以下区域成键电子存在强烈的共价键作用。
The structural stability, elastic properties and electronic structure of Mg17Al12, Al2Y and Al2Ca phases were calculated using Castep and Dmol programs based on density functional theory. The calculation results of heat of formation and binding energy show that Al2Y has the strongest alloying formation ability and structural stability. The calculation results of thermodynamic properties show that the Gibbs free energy of Al2Y is always the smallest in the range of 298-573 K, and its structure is thermally stable The best of which is Al2Ca followed by the worst of Mg17Al12. The formation of Al2Y and Al2Ca by Y and Ca alloyed Mg-Al alloys can improve the high temperature creep resistance of magnesium alloy. The calculation of elastic constants shows that all three intermetallic compounds As the brittle phase, the plasticity of Mg17Al12 is the best. The melting point of Al2Y predicted by the elastic constants is the highest and the thermal stability of Mg17Al12 is the best. The calculated results of state density and Mulliken electron occupancy show that the most stable Al2Y structure is mainly due to the strong covalent bonding of the bond-forming electrons in the region below the Fermi level.