الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 203 |  |  |
| | | from | 203 | | |
Abstract
Austempered ductile iron is a range of materials with different mechanical properties depending on the parameters of the austempering process. It is used in many applications and its uses are widely increasing, as in applications where the material is under fatigue stresses such as gears and crank shafts.
In this study, austempering was carried out on ductile iron with different austempering parameters and their effect on the resulted microstructure was investigated. The effect of austempering process on hardness and impact was also investigated. Also, fatigue testings of austempered ductile iron were carried out and the effect of austempering parameters on the fatigue life w as i nvestigated t o obtain the optimum austempering parameters to get better fatigue strength of austempered ductile iron. The relationship between the microstructural parameters of austempered ductile iron (namely the graphite nodules mean diameter, the graphite nodules count per mm2, and the volume fraction of retained austenite) and the fatigue life was also explored. Fatigue experiments of austempered ductile iron pre-cracked specimens were conducted to determine the effect of crack size on the fatigue life. The effect of stress intensity factor on the fatigue life of austempered ductile iron was also studied. The crack initiation and propagation during fatigue experiments were investigated by measuring the deflection at the free end of cantilever supported test specimens using data acquisition system with linear variable displacement transducer and the deflection curves were used to determine the portion of life for crack initiation and propagation. Scanning electron microscope was used to study the movement of cracks in austempered ductile iron specimens during fatigue experiments.