Study on the Microstructure and Liquid Phase Formation in a Semisolid Gray Cast Iron

Autor: Kazuyuki Kohama, Hajime Yamamoto, Davi Munhoz Benati, Kazuhiro Ito, Eugênio José Zoqui
Rok vydání: 2017
Předmět:
Zdroj: Metallurgical and Materials Transactions B. 48:2293-2303
ISSN: 1543-1916
1073-5615
DOI: 10.1007/s11663-017-1018-5
Popis: The development of high-quality semisolid raw materials requires an understanding of the phase transformations that occur as the material is heated up to the semisolid state, i.e., its melting behavior. The microstructure of the material plays a very important role during semisolid processing as it determines the flow behavior of the material when it is formed, making a thorough understanding of the microstructural evolution essential. In this study, the phase transformations and microstructural evolution in Fe2.5C1.5Si gray cast iron specially designed for thixoforming processes as it was heated to the semisolid state were observed using in situ high-temperature confocal laser scanning microscopy. At room temperature, the alloy has a matrix of pearlite and ferrite with fine interdendritic type D flake graphite. During heating, the main transformations observed were graphite precipitation inside the grains and at the austenite grain boundaries; graphite flakes and graphite precipitates growing and becoming coarser with the increasing temperature; and the beginning of melting at around 1413 K to 1423 K (1140 °C to 1150 °C). Melting begins with the eutectic phase (i.e., the carbon-rich phase) and continues with the primary phase (primary austenite), which is consumed as the temperature increases. Melting of the eutectic phase composed by coarsened interdendritic graphite flakes produced a semi-continuous liquid network homogeneously surrounding and wetting the dendrites of the solid phase, causing grains to detach from each other and producing the intended solid globules immersed in liquid.
Databáze: OpenAIRE
Externí odkaz: