Inoculation Effects of Cast Iron

The paper presents a solidification sequence of graphite eutectic cells of A and D types, as well as globular and cementite eutectics. The morphology of eutectic cells in cast iron, the equations for their growth and the distances between the graphite precipitations in A and D eutectic types were analyzed. It is observed a critical eutectic growth rate at which one type of eutectic transformed into another. A mathematical formula was derived that combined the maximum degree of undercooling, the cooling rate of cast iron, eutectic cell count and the eutectic growth rate. One type of eutectic structure turned smoothly into the other at a particular transition rate, transformation temperature and transformational eutectic cell count. Inoculation of cast iron increased the number of eutectic cells with flake graphite and the graphite nodule count in ductile iron, while reducing the undercooling. An increase in intensity of inoculation caused a smooth transition from a cementite eutectic structure to a mixture of cementite and D type eutectic structure, then to a mixture of D and A types of eutectics up to the presence of only the A type of eutectic structure. Moreover, the mechanism of inoculation of cast iron was studied

Thin Wall Ductile Iron Castings: Technological Aspects

The paper discusses the reasons for the current trend of substituting ductile iron castings by aluminum alloys castings.However, it has been shown that ductile iron is superior to aluminum alloys in many applications. In particular it has beendemonstrated that is possible to produce thin wall wheel rim made of ductile iron without the development of chills, coldlaps or misruns. In addition it has been shown that thin wall wheel rim made of ductile iron can have the same weight, andbetter mechanical properties, than their substitutes made of aluminum alloys

Structure Homogeneity and Thermal Stability of Austempered Ductile Iron

Abstract Solid-state transformation during heat treatment is of great practical importance because it significantly affects the final structure, properties, and thermal stability of cast components. The present study highlights the issue of structure formation and its effect on the thermal stability of high-quality cast iron, namely, austempered ductile iron (ADI). In this study, experiments were carried out for castings with a 25-mm-walled thickness and under variable heat treatment conditions, i.e., austenitization and austempering within ranges of 850 °C to 925 °C and 250 °C to 380 °C, respectively. The X-ray diffraction (XRD) investigations were carried out within a range of − 260 °C to + 450 °C to study the structure parameters related to the XRD tests, which provided information related to the phase participation, lattice parameters, and stresses in the microstructure as well as with an expansion of the crystal lattice. The results also provide insight into the role of the structure and its homogeneity on the thermal stability of ADI cast iron. The present work also aims to develop strategies to suppress the formation of blocky-shaped austenite in the ADI structure to maintain a homogeneous microstructure and high thermal stability

Angular dimensions of planetary nebulae

We have measured angular dimensions of 312 planetary nebulae from their images obtained in Halpha (or Halpha + [NII]). We have applied three methods of measurements: direct measurements at the 10% level of the peak surface brightness, Gaussian deconvolution and second-moment deconvolution. The results from the three methods are compared and analysed. We propose a simple deconvolution of the 10% level measurements which significantly improves the reliability of these measurements for compact and partially resolved nebulae. Gaussian deconvolution gives consistent but somewhat underestimated diameters compared to the 10% measurements. Second-moment deconvolution gives results in poor agreement with those from the other two methods, especially for poorly resolved nebulae. From the results of measurements and using the conclusions of our analysis we derive the final nebular diameters which should be free from systematic differences between small (partially resolved) and extended (well resolved) objects in our sample.Comment: 10 figures, 2 table

Correlation between the band-gap energy and the electrical conductivity in MPr2W2O10 tungstates (Where M = Cd, Co, Mn)

The values of the direct allowed energy gap determined from the UV-vis-NIR measurements and Kubelka– Munk transformation decrease from 3.38 via 2.70 to 2.42 eV for MPr2W2O10 in the sequence M = Cd, Co, Mn, while the values of the activation energy increase from 0.11 via 0.44 to 0.47 eV in the same sequence. In other words, the higher the activation energy, the smaller the energy gap. Because the energy gap is typical for insulators, so electron transport phenomena are considered under the Poole–Frenkel effect and small-polaron mechanism