Suchy, Jozef S.; Haberl, Katharina and Schumacher, Peter (2012). Effect of SiC reinforcement particles on the grain density in a magnesium-based metal-matrix composite: modelling and experiment. Acta Materialia, 60(6-7) pp. 2950-2958.For guidance on citations see FAQs.
AbstractThe aim in this work is to develop a numerical model capable of predicting the grain density in the Mg-based matrix phase of an AZ91/SiC composite, as a function of the diameter and total mass fraction of the embedded SiC particles. Based on earlier work in a range of alloy systems, we assume an exponential relationship between the grain density and the maximum supercooling during solidification. Analysis of data from cast samples with different thicknesses, and mass fractions and particle diameters of added SiC, permits conclusions to be drawn on the role of SiC in increasing grain density. By fitting the data, an empirical nucleation law is derived that can be used in a micro-macro model. Numerical simulations based on the model can predict the grain density of magnesium alloys containing SiC particles, using the diameter and mass fraction of the particles as inputs. These predictions are compared with measured data.
The paper presents results of measuring thermal conductivity of sand mould material and time of castings solidification evaluated from cooling curves and from Nova Flow & Solid numerical calculations. During the experiments pure Al (99,95%) plate was cast into the sand moulds. The analysed variable parameter in numerical calculations was mould thermal conductivity of fixed value taken from the range 0.5-0.9 W/(mK). Other mould parameters (initial temperature, mass density, heat capacity) and thermo-physical properties of liquid and solid casting were taken invariable. Basing on the measurements it was stated that thermal conductivity of the moulding sand has complex temperature variability, especially during the water vaporization and the obtained dependence should be used in the numerical calculations to improve their accuracy.
Solute segregation and formation of non-metallic inclusions during the solidification of a titanium-containing steel are modeled in this paper. The Ueshima model was used to describe the partitioning of solute elements in the steel, taking account of back-diffusion into the solid. Calculations were made for solidification of an AH-36-3u steel ingot cooled at 50 or 100 K min −1 . The simulations reveal that MnS inclusions are formed first, followed by TiN, Ti2O3 and SiO2. Increased cooling rate accelerates the formation of non-metallic inclusions, but for the assumed rates of 50 and 100 K min −1 the differences in amount formed are minimal. The results of these calculations for AH-36-3u steel give an approximate picture of the distribution of inclusions in the solidified ingot structure.K e y w o r d s : segregation, ingot solidification, non-metallic inclusions, back-diffusion
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