一方向凝固した純アルミニウムおよび希薄Al-Zn合金の固相-液相界面の組織について

抄録

The transition of solid-liquid interface morphologies in unidirectionally solidified aluminum and aluminum-zinc alloys was investigated in relation to the freezing conditions and the redistribution of solute.
The morphology of solid-liquid interface in 99.997% aluminum changed from plane to depression, irregular cell, elongated cell, hexagonal cell, successively, with the decrease in the ratio of (temperature gradient, G)/(freezing rate, R). Each critical value of G/R for each transition of morphology was constant.
On the other hand, the critical values of G/R in aluminum-zinc alloys were larger than those in aluminum and depended upon the zinc contents. The morphologies of depression and irregular cell were formed in wide ranges of G/R and zinc concentration.
Solute segregation at depressions was found on the irregular cell interface in aluminum-0.50% zinc alloy solidified at G/R=11.6×10³°C. sec/cm², and its concentration of zinc was 0.91.4%. However, the zinc concentration at cell nodes was 2.02.4% on the hexagonal cell interface at G/R=4.1×10³°C. sec/cm².