Abstract
<p>The as-cast and heat-treated structure of permanent mould castings of AlMg<sub>5</sub>Si<sub>2</sub>Mn alloys with different contents of Ti has been investigated by differential scanning calorimetry, hardness and microhardness measurements, tensile tests and fractography analyses, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray analysis. We have established that α-Al dendrites can be nucleated on an Al-Ti substrate, and also that primary Mg<sub>2</sub>Si crystals can be nucleated on oxides, including oxides of Al and Ti compounds. The dependence of the change in mechanical properties on ageing time, and on the amount of Ti in the alloys, is shown.</p>
Highlights
In recent years, the key adjectives in the design of new materials have been light-weight, low-cost and ecological
Recent decades have seen the birth of thixo- and rheo-casting processes, which deal with semi-solid state alloys
This line of investigation is especially important for casting alloys, because alloys. The (Al) is one of the few metals that can be cast by all of the processes used in metal casting
Summary
The key adjectives in the design of new materials have been light-weight, low-cost and ecological. While the first and second evolution processes mentioned above are of vital importance for improving casting properties and casting quality, the third process - developing new alloys — is in great demand for elaborating new cost-effective casting processes and for designing innovative components for the generation of vehicles: trains, ships and airplanes. The low Si concentration in a solid solution (about 0.2 at%) allows additional alloying (saturation) of the Al matrix by a wide range of elements, such as Zn, Cu, Sc, Zr, Cr, Ti, Li, or combinations of these alloys. They cannot be added to conventional Al-Si-Mg casting alloys due to the formation of silicides. As in the case of heat treatment, the effect of alloying AlMg5Si2Mn with Ti + Zr on the structure formation and properties have not yet been dealt with satisfactorily
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