On Factors Influencing Macro Shrinkage Porosity Formation in Compacted Graphite Iron

Vazehrad, Sadaf; Elfsberg, Jessica; Diószegi, Attila

doi:10.4028/www.scientific.net/msf.790-791.429

Cited by 8 publications

(11 citation statements)

References 7 publications

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“…On the left of this figure, the micrograph demonstrates that dendrites and the matrix around large primary nodules transformed to ferrite, whilst the remaining of the structure consisted in pearlite. This is clearly related to the higher silicon content of austenite formed early during solidification and much in line with observations reported by Vazehrad [10].…”

Section: Discussionsupporting

confidence: 91%

Effect of Cooling Rate on the Eutectoid Transformation in Compacted Graphite Cast Iron

Lacaze

Thébault

Freulon

et al. 2018

MSF

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Differential thermal analysis has been used to characterize the effect of cooling rate on the eutectoid transformation of a compacted graphite iron. The samples were machined out from an as-cast thermal cup, austenitized at 950°C and then cooled to room temperature at various rates within the range 1−55.5°C/min. It was found that even at the highest investigated cooling rate, significant amounts of ferrite could be observed. When comparing the microstructure before and after Nital etching on samples cooled at intermediate cooling rates, it appeared that ferrite formed preferentially along the worms. This is discussed in terms of graphite shape and microsegregation and this latter seems prevalent. Finally, analysis of the thermal records was performed to characterize the temperatures for the start of the stable and metastable eutectoid reactions which confirms the eutectoid transformation sets up in compacted graphite irons as in lamellar and spheroidal graphite irons.

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Section: Discussionsupporting

confidence: 91%

Effect of Cooling Rate on the Eutectoid Transformation in Compacted Graphite Cast Iron

Lacaze

Thébault

Freulon

et al. 2018

MSF

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“…This behaviour suggests that austenite and compacted graphite growth is coupled, in analogous manner of LGI. Recently Vazehrad et al 16 have employed a colour etching technique as a tool to analyse and measure the eutectic colonies of coupled growth present in CGI samples with shrinkage porosity.…”

Section: Introductionmentioning

confidence: 99%

Study of the solidification structure of compacted graphite cast iron

López

Rivera

Massone

et al. 2016

International Journal of Cast Metals Research

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This investigation focuses on the study of the solidification mechanism of compacted graphite cast iron (CGI). The solidification macrostructure was revealed in cast samples using a special technique known as direct austempering after solidification (DAAS). The microstructure was revealed by colour etching. The results were compared with earlier investigations of the solidification of spheroidal (SGI) and lamellar (LGI) graphite irons, and show that, similarly to other free graphite cast irons, the solidification of CGI is dominated by the presence of relatively large grains of austenite that can be observed with bare eyes. The CGI cast samples show a typical ingot structure, containing columnar and equiaxed grains, with a narrow columnar to equiaxed transition. The microstructure analysis showed that a dendritic substructure and a large number of eutectic colonies form the grains. Microsegregation is located inside the grains, mostly between secondary dendrite arms. The results indicate that the growth mechanism during solidification of CGI resembles that of LGI, but not the mechanism of SGI.

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“…The low reproducibility and non-uniformity of the coloring make the use of conventional color-based image analysis on the raw micrographs difficult. Nevertheless, with this tool at their disposal, cast iron researchers have begun exploring the nature and role of the early microstructure of LGI, CGI, and SGI [4,6,11,13,14]. Some have started looking into research done on other materials where the dendritic structure has already been studied for decades and have attempted to extend the knowledge to cast iron.…”

Section: Dendritic Austenite In As-cast Graphite Ironsmentioning

confidence: 99%

Quantification of Dendritic Austenite After Interrupted Solidification in a Hypoeutectic Lamellar Graphite Iron

Domeij

Hernando

Diószegi

2015

Metallogr. Microstruct. Anal.

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This paper presents an unconventional etching technique to reveal the microstructure in a hypoeutectic lamellar graphite iron that has been quenched after isothermal heat treatment in the proeutectic semi-solid temperature region. A technique for quantifying the dendrite microstructure using the aforementioned etching technique involving a combination of a raster graphics editor and an image analysis software is outlined. The agreement between this quantification technique with regard to volume fraction and surface area per unit volume of the dendritic austenite and corresponding point counting and line intercept techniques is analyzed. The etching technique was found useful but sporadic tinting of martensite was problematic. Some measurements showed significant systematic disagreement which correlated with the coarseness of the measured dendrites. Most systematic disagreement is attributed to difficulties in defining the dendrite boundary in the analogues and much of the random disagreement to easily identified discrepancies between the analogue and the micrograph.

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On Factors Influencing Macro Shrinkage Porosity Formation in Compacted Graphite Iron

Cited by 8 publications

References 7 publications

Effect of Cooling Rate on the Eutectoid Transformation in Compacted Graphite Cast Iron

Effect of Cooling Rate on the Eutectoid Transformation in Compacted Graphite Cast Iron

Study of the solidification structure of compacted graphite cast iron

Quantification of Dendritic Austenite After Interrupted Solidification in a Hypoeutectic Lamellar Graphite Iron

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