Abstract
Effects of supercooling and cooling rate on the solidified structures of Al–Mn, Al–Cr and Al–Zr alloys, which had a strong tendency to form metastable solid solution by rapid cooling of the molten alloys, were investigated by means of thermal analysis and microscopic observation. The results obtained were as follows:
(1) The square of the degree of supercooling was proportional to the cooling rate on the solidification of the alloys having a solute concentration up to the maximum solid solubility limit at equilibrium (Ce). At solute concentrations higher than Ce, this relation was satisfied under the conditions that the primary crystals were a super-saturated solid solution.
(2) The minimum cooling rate to form the super-saturated solid solutions containing more solute atoms than Ce was 115, 175 and 190°C/sec for Al–Mn, Al–Cr and Al–Zr respectively.
(3) Metastable phase diagrams were proposed under varying conditions of composition, temperature and cooling rate in the Al–Mn, Al–Cr and Al–Zr systems.
