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The formation of eutectics in Al–Zn–Mg–Ni and Al–Zn–Mg–Si systems is studied by means of metallography, DSC, EPMA, X-ray spectroscopy and thermodynamical calculations. Polythermal sections of the corresponding phase diagrams are constructed. The concentrations and temperatures of binary eutectic reactions L → (Al) + Al3Ni and L → (Al) + Mg2Si in quaternary alloys are determined. Nonequilibrium solidification in Al–7% Zn–3% Mg-based alloys ceases at approximately 480 °C. The alloys close by composition to binary eutectics have considerably improved casting properties as compared to the base Al–7% Zn–3% Mg composition. In particular, hot tearing susceptibility is much less in alloys with Al3Ni or Mg2Si. These results are corroborated by measurements of thermal contraction during solidification. The alloys containing binary eutectics exhibit much lower temperatures of contraction onset and less thermal strain is accumulated in the solidification range. Fine eutectic morphology enables fragmentation and spheroidization of intermetallic particles during annealing. The presence of Al3Ni and Mg2Si particles does not decrease the precipitation hardening effect associated with precipitation of the T′ (AlMgZn) phase. Improved casting properties and good mechanical properties of castings allow the application of Al–Zn–Mg alloys with binary eutectics formed by Al3Ni or Mg2Si as foundry alloys.

The solidification of an Al-4.5 pct Cu alloy in a shallow cavity under conditions of forced flow was studied both by fluid-dynamics simulations with solidification included and by experiments. The variation in bulk-flow velocity and initial superheat dramatically changes the macro-and microstructure, promoting grain refinement, an equiaxed-to-columnar transition (ECT), the formation of peculiar grain and dendrite morphologies, etc. The solidification parameters during solidification in the shallow cavity under forced-flow conditions have been determined by computer simulations and partially compared with the experimental results. The interaction between flow vortices and the progressing solidification front and its effect on structure evolution have been analyzed. Finally, quantitative correlations between microstructure, solidification, and flow parameters have been established.

The purification of gaseous and liquid media by means of a cyclone concept is well known and has been successfully applied in different industries. While the impurities removal from molten metal has been an important issue for many years, to the best of our knowledge, the application of a cyclone concept has rarely been considered for molten metal applications. The presence of impurities in cast products is detrimental to their quality. In this article, computer simulations are used to evaluate the possibilities of cyclone application in molten aluminum processing by determining the following: the fluid flow for flow velocities of 0.01, 0.1, and 1 m/s; the particle behavior for discrete particle sizes in the range of 20 to 100 lm; and the collection efficiency of the cyclone. The geometrical features are discussed. The results show that the cyclone concept can be effectively used as an alternative method to remove the impurities from a stream of molten aluminum in a wide range of flow regimes.