Published online by Cambridge University Press: 06 March 2019
Austempered ductile cast iron (ADI) lias microstructures that consist of martensite and of retained austenite. ADI has very toughness compared with cast iron heat-treated differently. The retained austenite near fracture surfaces transforms to martensite when fracture occurs.
In the present study, X-ray fraetography is applied to fatigue fracture surfaces of ADI. The fatigue tests were carried out on compact tension (CT) specimens. The volume fraction of retained austenite was measured quantitatively and the line broadening of X-ray diffraction profiles was measured on and beneath fatigue fracture surfaces. The depth of the plastic zone left on fracture surfaces was evaluated from line broadening. The results are discussed on the basis of fracture mechanics.