The aim of 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 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 of added SiCp, permits conclusions to be drawn on the role of SiCp in increasing grain density. By fitting the data, an empirical nucleation law is derived that can be used in a micro model. Numerical simulation based on the model can predict the grain density of magnesium alloys containing SiC particles, using the mass fraction of the particles as inputs. These predictions are compared with measured data.

The presented access the influence of Mn content (0-0.94 wt.%) on the course of the cooling curves, phase transformation, macrostructure, and microstructure of Al-Cu alloys for three series: initial (Series I), with the addition of an AlTi master (Series II), and modified with AlTi5B1 (Series III). The maximum degree of undercooling ΔT was determined based on the cooling curves. The surface density of the grains (NA) was determined and associated with the inverse of solidification interval 1/ΔTk. Titanium (contained in the charge materials as well as the modifier) has a significant effect on the grinding of the primary grains in the tested alloys. A DSC thermal analysis allowed for the determination of phase transition temperatures under conditions close to equilibrium. For series II and III, the number of grains decreases above 0.2 wt.% Mn with a simultaneous increase in solidification interval 1/ΔTk. The presence of Al2Cu eutectics as well as the Cu-, Fe-, and Mn-containing phases in the examined samples was demonstrated using scanning electron microscopy.