Supporting the model of ductile iron dendritic solidification

• Author(s): Santos, Henrique ; Pinto, A. M. P. ; Jacinto, Maria ; Sá, Carlos
• Date: 2000
• Persistent ID: http://hdl.handle.net/1822/1786
• Origin: RepositóriUM - Universidade do Minho
• Subject(s): Ductile Iron; Solidification
• Document Type: Article
• Language: Portuguese

Description

The literature about graphite formation in ductile iron proposes the experimentally supported theory lhat this phase forms in the melt. This is naturally accepted as a consequence af the euteclic reaction of the iron-carbon equib"briumdiagram. This reaction requires that during cooling, at 1150-1100°C, the liquid with a eutectic composition decomposes into two solid phases, pure graphite aOOaustenite with a earbon content dose to 2% in weight. li the ductile irons have a generaIly eutectic composition, the presence of neither pro-eutectic graphite nor austenite seems necessary for eutectic graphite formation. According to the proposed solidification path, the graphite nodules become encapsulated by an austenite case, resulting in a 10ss of conmct between liquid and graphite. Carbon will then have to diffuse from the liquid through the austenite to the graphite to allow further growth 01both solid phases.