Austempered ductile iron (ADI) is a group of ductile irons offering the design engineers remarkable mechanical properties. It exhibits an excellent combination of high strength, ductility, toughness, fatigue strength, and exceptional wear resistance that is unavailable in other grades of cast iron. Austempered ductile iron is almost twice as strong as the regular ASTM grades of ductile iron, whilst still retaining high elongation and toughness characteristics. In addition to the exceptional wear resistance and fatigue strength, it enables designers to reduce a component's weight and costs for equivalent or improved performance. Therefore, ADI has become an attractive and economic substitute for forged steel and cast steel in many engineering applications. This led to marked interest in ADI in the past few years with considerable research work to understand the effect of processing parameters on its characteristics and mechanical properties. The objective of this paper was to review works that have been conducted over the past years on the effects of process variables, mechanical properties, benefits, and applications of ADI.
This study focussed on the work hardening behaviour and microstructure of austenitic manganese steel relative to premature failure of crusher jaws. Samples of sound and failed crusher jaws were taken, the change with depth from the working surface to the sample core was measured and their microstructures observed. The study revealed a sharp hardness gradient in the failed crusher jaws, and presence of large carbides at both the austenite grain boundaries and in the austenite matrix. The failure of crusher jaws was attributed to brittle fracture as a result of precipitates of carbides from the inability of precipitated carbides to absorb shock during impact working. Finally, we conclude that the failure occurred as a result of inadequate quenching operations during the manufacturing process that resulted in the formation of carbide precipitates which embrittle the austenitic manganese steel, reduce its ability to withstand shock and create a non uniform plastic flow as it is work hardening.
Corrosion behaviour of cast iron and low alloy steel in cocoa liquor and well water was investigated. The average weight losses of the specimens were measured using digital weighing balance. The results showed that the weight losses of both cast iron and low alloy steel in both media increases with time. Corrosion rate of cast iron in cocoa liquor increases rapidly with time for up to 336 hours (1000 µm/yr), but in well water the rapid rate of corrosion only lasted up to 187 hours (1160 µm/yr) thereafter it continuously dropping until 264 hours (667 µm/yr) after which it remains constant. Low alloy steel corroded faster in cocoa liquor up to 264 hours (200 µm/yr), whereas the initial rapid corrosion rate only lasted up to 168 hours (180 µm/yr) in well water environment. The results revealed that low alloy steel exhibited better corrosion resistance in both media, with cocoa liquor been more aggressive. Thus, low alloy steel will be a better material for piping and pumping system in cocoa processing industries.
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