Abstract
On the lattice transformation occurring in case of supercooling of γ phases of the Fe-C and Fe-Ni alloys the following notable phenomena were observed; Lattice transformation can scarcely proceed at a temperature at which it begins even if the alloy is preserved for long hours at that temperature. There exists a characteristic interval of temperature which has little connection with cooling rate except for the extreme cases of higher or lower cooling rate. Temperature intervals rather increase when the cooling rate is extremely small after the transformation begins. If cooling is then continued again,it does not occur at once but after leaving a considerable shift of temperature it follows to progress again. In this case the larger the amount which had transformed before interruption of cooling,or the longer the duration of interruption, the larger the shift of temperature is.
The phenomena concerning the items(1) and (2) mentioned above were discussed in the 1st report in which the phenomena of temprature interval were reduced to that of the strain-hardening in the plasticity by assuming a relation that the free energy difference dissipated in the lattice transformation γ→α was equal to the mechanical energy required for plastic gliding-like deformation on the occasion of transformation. On the same stand point we can reduce the phenomena of the items(3) and (4) to the effect of loading rate on the stress-strain relation and the age hardening in worked metals respectively.
The observed thermal dilatation curves showing the temperature interval under various cooling rate (Fig. 1) can be rewritten in the form of stress-strain curves under various loading rates (Fig. 2) through the above relation. These figures show that the above consideration seems to be reasonable.
