A synthesis of the low- and medium-cycle fatigue behaviour of as cast and austempered ductile irons based on the plastic strain energy

The use of ductile irons for structural applications is increasing thanks to their interesting mechanical properties, which can be combined with the casting technology to manufacture components having complex geometries. Mechanical properties can be adjusted by varying the chemical composition and the heat treatment parameters (temperatures and holding times). In this paper the fatigue behaviour of some ductile irons in the as-cast as well as in the austempered conditions was investigated. Push-pull, strain-controlled fatigue tests were carried out on ferritic, pearlitic, isothermed and austempered ductile irons covering a range of tensile strengths from about 400 MPa to 1300 MPa. Material parameters of the strain-life were fitted on experimental results in order to assure compatibility. Despite the wide range of tensile strengths, the fatigue behaviour of the different ductile irons could be synthesized on the basis of the plastic strain hysteresis energy.