Transmission electron microscope(TEM) was used to investigate the microstructure of an austempered ductile iron. Specimens were austenitised at 900℃ for 1h and then austempered at 370℃ for 1h. It was found that the microstructure of graphite was in form of layers which radiated from graphite nodular center. The matrix microstructure consisted of carbide free bainitic ferrite together with retained austenite, which presented in two kinds of morphology. One is the alternating lath like regions of bainitic ferrite and retained austenite. The other is the massive austenite distributed in the Bainitic ferrite .
Journal of Chinese Electron Microscopy Society