Investigation of the Growth of Bainite in Fe-Ni-C Alloys by Hot Stage Microscopy (The Study on the Mecanism of Bainite Reaction I)

Abstract

The growth of bainite relief in Fe-6%Ni-alloys with various carbon contents was studied by hot-stage microscopy, and its edgewise growth rate was determined over the temperature range 200°∼500°C. The results are as follows: (1) The dependence of the growth rate both on temperature and carbon content is consistent with the prediction from the theory that the growth rate of bainite is controlled by the diffusion of carbon in austenite near the austenite-ferrite interface. (2) The values of the growth rate obtained are always about 1/30 of the corresponding values predicted from the above theory for the iron-carbon system. This difference can be largely attributed to the effect of nickel on the equilibrium content of carbon in austenite at the austenite-ferrite interface. (3) In comparison with the other results published so far, the growth rate of bainite appears to decrease exponentially with the nickel content at the same temperature and carbon content.