Heat treatment of a casting elements poured from silumins belongs to technological processes aimed mainly at change of their mechanical

properties in solid state, inducing predetermined structural changes, which are based on precipitation processes (structural strengthening of

the material), being a derivative of temperature and duration of solutioning and ageing operations. The subject-matter of this paper is the

issue concerning implementation of a heat treatment process, basing on selection of dispersion hardening parameters to assure

improvement of technological quality in terms of mechanical properties of a clamping element of energy network suspension, poured from

hypoeutectic silumin of the LM25 brand; performed on the basis of experimental research program with use of the ATD method, serving

to determination of temperature range of solutioning and ageing treatments. The heat treatment performed in laboratory conditions on a

component of energy network suspension has enabled increase of the tensile strength Rm and the hardness HB with about 60-70%

comparing to the casting without the heat treatment, when the casting was solutioned at temperature 520 o

C for 1 hour and aged at

temperature 165 o

C during 3 hours.

The article presents the investigations of 7xxx aluminium alloys performed by the method of thermal and derivational analysis. The studies made it possible to identify the effect of the changes in the Cu concentration, the total Zn and Mg weight concentrations and the Zn/Mg weight concentration ratio on their crystallization process: the cooling as well as the kinetics and dynamics of the thermal process of cooling and crystallization. Metallographic studies were performed on the microstructure of the examined alloys and their HB hardness was measured. The evaluation of the changes was presented in reference to the model alloys EN AW-7003 and EN AW-7010, whose microstructure under the conditions of thermodynamic equilibrium are described by the phase diagrams: Al-Zn-Mg and Al-Zn-Mg-Cu. The performed investigations confirmed that the hardness HB of the examined alloys is mainly determined by the reinforcement of the matrix αAl by the introduced alloy additions and the presence of phases Θ(Al2Cu) and S(Al2CuMg) rich in copper, as well as η(MgZn2), in the examined alloys' microstructure. The increase of the amount of intermetallic phases precipitated in the microstructure of the examined alloys is caused, beside Cu, by the characteristic change of Zn wt. concentration and Mg. It was proposed that the process of one-stage thermal treatment of the examined alloys be introduced at a temperature of up to tJ-20 °C, which will prevent the exceedance of the solidus temperature.