Dilatation analysis of the eutectoid transformation of the as‐cast spheroidal graphite cast iron

Abstract

It is known that the decomposition of austenite in spheroidal graphite cast iron (SGI) depends on numerous factors. Among them, the cooling rate and microsegregation of alloying elements (Si, Cu, Mn) are derived from the solidification step. The eutectoid transformation of the SGI has been investigated with a new dilatometer that was made for the investigation of cast iron alloys. The temperature dependence of the dilatations, similar to a function of time is shown by the dilatation curves. The investigation of the eutectoid transformation has been examined by the evaluation of dilatation curves, metallographic examinations and chemical compositions. It is possible to exactly follow the eutectoid transformation of austenite, which proceeds according to the stable reaction in ferrite and graphite (γ → α + graphite), the metastable reaction in perlite (γ → α + Fe 3 C), or dilatometric and differential dilatometric curves, respectively. The ratio between the perlite and ferrite phase in the matrix of the spheroidal graphite cast iron depends upon the extent of each reaction. The temperature difference between the dilatation extremes during the eutectoid reactions, as a function of the ferrite fraction, has been determined. A correlation between the amount of ferrite and the characteristic expansion owing to the graphite precipitation was found.

Control of Microstructure during the Eutectoid Transformation in the As‐cast Spheroidal Graphite Cast Iron with »in‐situ« Dilatation Analysis and Quenching Experiments

“…The set-up of the "in situ " dilatometer is shown in Figure 1. In a previous study [13] the eutectoid transformation had been obtained from "in situ" measurements, the experimental results are presented in Figure 2. In order to study the eutectoid transformation kinetics, "in situ" quenching experiments were carried out together with dilatometric analyses .…”

“…Sampling and metallographic analysis. The samples for the metallographic analysis were prepared from the dilatated and quenched specimens, which were cut through the measuring height line [13]. The fractions of the particular microstructure constituents (graphite, ferrite, pearlite and/or martensite) were evaluated by optical microscopy (Nikon Microphot FXA -3CCD) linked with computer aided metallographic analysis (image analySIS 3.0 according to standard EN ISO 945).…”

“…From the cooling curve, the cooling rate of 105 K/min was calculated. In the linear dependence between ferrite fraction and expansion at the eutectoid transformation as well as between ferrite fraction and temperture difference between the dilatation extremes, some scattering is observed., which is due to differences in chemical composition [13] (the degree of saturation is between 0.74 and 1.03). Figures 8 and 9 show the relations between the pearlite fraction and the temperature difference between the dilatation extremes, as well as between pearlite fraction and total concentration of Cu and Mn.…”

Microstructural analyses of two high noble gold-platinum alloys before and after conditioning in a cell culture medium

“…The measurements were carried-out in a protective atmosphere of inert gas Ar 5.1. The specimens were heated-up to 1573 K at a heating rate of 10 K/min, isothermally kept at 1573 K for 10 min and cooled at the same cooling rate to room temperature [12]. STA analyses resulted in differential scanning calorimetry (DSC) cooling and heating curves.…”

Selection of electrodes for the ˝in situ˝ electrical resistivity measurements of molten aluminium

“…Several methods exist for characterization of solidification of metal materials using thermal analysis, metallographic analysis, dilatometry and electrical resistivity measurement described in literature [1][2][3].…”