Issues connected with high quality casting alloys are important for responsible construction elements working in hard conditions.

Traditionally, the quality of aluminium casting alloy refers to such microstructure properties as the presence of inclusions and intermetallic

phases or porosity. At present, in most cases, Quality index refers to the level of mechanical properties – especially strength parameters,

e.g.: UTS, YS, HB, E (Young’s Modulus), K1c (stress intensity factor). Quality indexes are often presented as a function of density.

However, generally it is known, that operating durability of construction elements depends both on the strength and plastic of the material.

Therefore, for several years now, in specialist literature, the concept of quality index (QI) was present, combines these two important

qualities of construction material. The work presents the results of QI research for casting hypoeutectic silumin type EN AC-42100

(EN AC-AlSi7Mg0.3), depending on different variants of heat treatment, including jet cooling during solution treatment.

The study presents the results of the investigations of the effect of Cu, Ni, Cr, V, Mo and W alloy additions on the microstructure and

mechanical properties of the AlSi7Mg0.3 alloy. The examinations were performed within a project the aim of which is to elaborate an

experimental and industrial technology of producing elements of machines and devices complex in their construction, made of aluminium

alloys by the method of precision investment casting. It was demonstrated that a proper combination of alloy additions causes the

crystallization of complex intermetallic phases in the silumin, shortens the SDAS and improves the strength properties: Rm, Rp0.2,HB

hardness. Elevating these properties reduces At, which, in consequence, lowers the quality index Q of the alloy of the obtained casts.

Experimental casts were made in ceramic moulds preliminarily heated to 160 °C, into which the AlSi7Mg0.3 alloy with the additions was

cast, followed by its cooling at ambient temperature. With the purpose of increasing the value of the quality index Q, it is recommended

that the process of alloy cooling in the ceramic mould be intensified and/or a thermal treatment of the casts be performed (ageing)(T6).