Abstract
In the preceeding papers (Mem. Ryojun Coll. Eng., 2, 1929, 205, 3, 1930, 87.3, 1931, 285 and 295.), one of the present writers pointed out, that the intermediate metastab'e phase β' exists during the course of the eutectoid-transformation of this alloy.
Thereafter, the existence of another metastable phase β1, was additionaly detected by Wassermann in the same alloy.
In the present paper, the crystal structure of various phases taking part in the said transformation is re-examined, and the change in structure due to the transformation is studied by means of X-ray, electrical resistivity and microscopic methods. Using the "Vacuumheitztisch nach Esser", the alloy containing 12·66% of Al is heated or cooled rapidly under the microscope, and the change in microstructure due to the metastable transformation β1 β', was photographed with a cinekodak on 16-mm. film. From the micro-cinema thus obtained, it is found that the well-known needle structure of the quenched alloys grows at first at about 300°C on cooling and disappears gradually at about 410°C on re-heating, and further that the needle itself has no phasic meaning; it would probablly be regarded as beeing due to the slip or shear of the lattice plane.
