α(Al)-Mg_2Ge伪二元共晶凝固与组织特点

Solidification and Structural Characteristics of Pseudobinary α(Al)-Mg_2Ge Eutectic

利用热分析和定向凝固等手段研究了Al-Mg－Ge系中α（Al）－Mg2Ge的共晶凝固特征。实验表明：在Al-Mg－Ge系中，具有最小凝固温度区间（△T为零）的两相共晶声、不处于具有严格化学配比（Mg与Ge原子分数比为2）的Al-Mg2Ge线上，而是偏向富Mg一侧。合金成分分布在伪二元线附近一定范围内时，发生二元共晶反应，在该范围以外时将有三元共晶反应出现。Mg2Ge以棒状形式存在，当凝固速度小于4cm/h此时，具有较好的取向效果，高于该速度时发生胞晶转变。棒间距与生长速度，λ1.34和V之间成线性关系。

Eutectic solidification characteristics of a(Al)-Mg,Ge in Al-Mg-Si system were in-vestigated by thermoanalysis and directional solidification techniques. It was demonstrated that the two-phase eutectic point which has a minimum solidification temperature scale (△T=0) in the Al-Mg-Ge system does not lie on the line of Al-Mg,Ge that has a strict stoichiometric composition ratio (Mg/Ge=2), shifting to the Mg-rich side. Binary eutectic reaction occurs if the composition of the alloy locates in the area near the pseudobinary line, while the ternary eutectic reaction occurs when the composition is out of this range- Phase Mg,Ge adopts a rod shape, which has a fine orientation when the solidification velocity is below 4cm/h and cellular transform occurs when the velocity is above this value. Relationship between the interrod spacing and the growth velocity fits a linear equation.