Abstract
The structure and properties of ductile iron are highly dependent on the solidification mechanism, and chills are used to promote directional solidification to obtain sound castings. A series of fracture toughness experiments was carried out, involving austempered chilled ductile iron containing 3·42%C, 1·8%Si, and other alloying elements. By using copper chills of different thicknesses, the fracture toughness with varying chill rate was examined. Fracture toughness tests were carried out using three point bend specimens, each with a chevron notch, according to ASTM Standard E399 : 1990. It was found that the fracture toughness of austempered chilled ductile iron is highly dependent on the location in the casting from where the test specimens are taken and also on the nickel and molybdenum contents of the material. Chill thickness, however, also affects the fracture toughness of the material.
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