Keizo Iwase

Some Remarks on the Transformation of Austenite

Ba sed upon the results obtained concerning. the A3 transformation of Fe-Ni alloys, some remarks on the transformation of austenite in carbon steel have been made, namely: (1) how the quantity of retained austenite in oil quenched specimen becomes greater than that in water quenched one, (2) what is an essential difference between the primary and secondary troostites, (3) on the cause of the irreversibility of the A3 transformation found in Fe-Ni alloys, and (4) martensite is a metastable α solid solution situating below the extension line of the solidus of A3 transfnrmation in the Fe-C diagram.

On the Temper-Hardenability of Nickel Alloys containing Silicon

Following the diagram on the solid solubility of silicon in nickel determined by one of the authors, the hardenability, by tempering of nickel alloys containing silicon quenched from temperatures, at which complete a solid solution is obtained, has been studied with the measurement of the Vickers hardness. In case of Ni-Si binary alloys the hardness of the quenched alloys at 1120° becomes larger as the increase of the silicon content in the alloys, the hardness increments of the quenched alloys by the tempering show maximum at the intermediate silicon content, 7% of silicon (Cf. Fig. 3), and the hardness of the annealed alloys are lower at 9%-, 8%- alloys and higher at 7%-, 6%- alloys than those of the solution-annealed and quenched alloys. The changes of the a solid solution range of Ni-Si alloys by addition of small amount of one kind of the following elements, Fe, Co, Al, Cu, Mn or Ag, at constant temperatures were determined by microscopic examination of the quenched specimens. The addition of 5% and 10% of Cu raises the hardnesses of alloys both of tempered and quenched states with the shortening of the tempering time required to attain the maximum hardness. The influence of 2% of Fe or 2% of Co on the temper-hardening of Ni-Si alloys resembles with each other. The both elements decrease the ageing rate of the alloys and make the temper-hardenability still large. The addition of Al hardens the alloys. the form of the time-hardness curve resembling that of Ni-Si binary alloys. The age-hardening property is observed in 5% Si-Ni alloy by the addition of Mn of more than 4%.