Disperse structure forming in rapidly quenched Al-Hf alloy

The structure of the Al-1.4 wt.% Hf alloy was investigated depending on overheating initial melt above liquidus and cooling rate at solidification. It was shown that varying melt overheating, one can control cast structure formation. The most disperse structure forms at the temperature slightly below 1470 K. According to results of viscosity measurements, the last temperature corresponds to irreversible homogenization of the melt. It was discovered that overheating the melt above its homogenization temperature results in grain coarsening, appearance of spherulite-like and dendrite forms of solid phase growth and formation of metastable α-solid solution abnormally over-saturated by hafnium.