镁合金熔体结构信息的价电子理论研究

EET Research on Melt Structural Information of Magnesium Alloy

摘要:

运用固体与分子经验电子理论（EET）对Mg-Al合金熔体进行价电子结构分析，在此基础上构建了基本结构模型，获得熔体的基本结构信息。通过分析升温和降温过程中镁合金熔体黏度-温度关系曲线V(t)的不可逆现象，间接地对熔体结构信息的不可逆变化作出判断。结果表明：原子间各键共价电子对数nα的差异是造成熔体结构信息变化的根本原因，直接导致合金熔体存在微观不均匀性；当温度升高至730 ℃附近时，结构相对稳定的原子集团内部的Al-MgIII(C)键开始发生断裂，熔体结构达到新平衡的相对均匀状态；遗传自固态组织中微观不平衡结构的消失和原子集团内部Al-MgIII键的破坏及原子发生的不可逆重排是曲线V(t)发生不可逆变化的本质原因。这对于深入认识镁合金熔体结构信息及探索凝固微观机制具有重要理论意义。

Abstract:

Through the empirical electron theory of solids and molecules (EET), the valence electron structure of Mg-Al alloy melt was analyzed. Based on the analysis, the basic structure model was established and the melt structural information was obtained. By analyzing the irreversible phenomenon of viscosity-temperature relationship curve V(t) of magnesium alloy melt in the temperature interval of ascent and descent, the irreversible change of the melt structural information would be judged indirectly. The results show that the number difference of covalent electron pair nα of each bond between atoms is the ultimate reason of the different melt structural information, which induces micro-inhomogeneity in alloy melt directly; at near 730 °C, Al-MgⅢ(C) bonds in the atomic clusters with relatively stable structure begin to break. At this time, the melt structure achieves a new equilibratory and relatively homogeneous state. Disappearance of micro-nonequilibrium structure inherited from solidified structure, breakage of Al-MgⅢ(C) bonds in the atomic clusters and irreversible rearrangement of atoms are the essential reason of irreversible change of curve V(t). It is very important for further understanding the melt structural information of magnesium alloy and exploring solidification micro-mechanics.