オーステンパー球状黒鉛鋳鉄の炭素の挙動に関するX線的検討

抄録

  Behaviors of carbon, retained austenite and bainitic ferrite, which exert important influences on mechanical properties of ADI, were studied in the temperature range 300-400°C using X-ray diffraction.
  Carbon diffuses fast at high temperature, causing to fast saturation of carbon in retained austenite, whereas slow diffusion of carbon occurs at low temperature.
  Totally, bainitic ferrite exists only in the early stage of the transformation at 350 and 440°C. However, bainitic ferrite can partially exist at 300°C because the transformation occurs inhomogeneously. Bainitic ferrite contains high carbon at low temperature, which may be caused by martensitic transformation. The carbon content in bainitic ferrite at high temperature on the other hand, is low, which suggests that carbides precipitate in carbon super-saturated retained austenite.
  Thus, the mechanism of bainitic transformation should vary depending on temperature, just as in steels.