Phenomena of the intermediate low temperature embrittlement of ferritic ductile cast iron

Abstract

To study the tensile behaviour of ferritic ductile cast iron in the intermediate low temperature range before the transition of upper elongation to lower elongation, three test materials of different carbon and silicon concentrations, namely 3.9C–2.9Si, 3.5C–2.7Si and 2.0C–2.1Si in wt%, were used. The test results indicate elongation deterioration in the temperature range of around—30°C, in which the fracture surfaces reveal zoned ductile and brittle appearance. Whereas pure dimple fracture occurs in the temperatures higher than the intermediate low temperature range, the ductile area of the zoned fracture is associated with the formation of dimple voids and tearing ridges. It is also subject to severe deformation and thus linking of graphite nodules can be observed. The zoned brittle area is covered by quasi-cleavage fracture. In contrast to the cleavage and quasi-cleavage fractures of the specimens deformed at the temperatures below the intermediate low temperature range, which are initiated around graphite nodules, zoned brittle fracture starts to form preferentially from the eutectic cell wall region.

Keywords:

• ferritic SG cast iron
• tensile properties
• intermediate low temperature embrittlement
• fracture appearance
• zoned ductile fracture
• zoned brittle fracture