Abstract
The history of progress and application of the hot-stage microscope were reviewed. Moreover its application in future was mentioned. A new type hot-stage microscope with 16mm cine camera developed by the authors was reported, and photomicrographs of the martensite and bainite transformation of Ni-Cr-Mo steel were explained.
By analysis of the film, it was observed that the martensite needles were formed abruptly at Ms point and successively with decreasing temperatures; the bainite needles nucleated and grew isothermally at transformation temperature.
The martensite transformation was the athermal "Umklappung" transformation by the shear process. And the bainite transformation proceeded with the nucleation rate and the coherent growth rate which depended on the transformation temperature. It seems that the growth rate of bainite needle was controlled by the diffusion rate of carbon.
The vacuum heating stage with loading mechanism was also manufactured by way of experiment, observation of steel during creep-rupture at elevated temperature was photographed in 16mm cine film, by use of this apparatus.
By analysis of the film, the structurad change during creep-rupture of steel were related with their creep curves. It was observed that the appearance of crack which led to the rupture occurred at the transition point between the secondary and the tertiary creep.
