Influence of Sr addition on microstructure of the hypereutectic Zn–Al–Cu alloy

The purpose of the presented work is to answer the questions: how does the addition of strontium to the Zn–8Al–1Cu alloy crystallisation kinetics influence? What will the significance of the low temperature of heat treatment, characteristic for eutectic Zn–Al alloys, have for the formation of intermetallic phases? To describe the phenomena that occur in the metal during solidification under various conditions caused by the variable cooling rate, and as a result of the application of modifiers that provide the basis for heterogeneous nucleation, it was decided to use thermal-derivative analysis method. The mentioned method allows to accurately describe and interpret the kinetics of crystallisation of the tested materials. The effectiveness of the modification was assessed based on a degree of fragmentation of the structural components and changes in the properties of the material being modified, as well as by analysis of the cooling curves of the tested alloys. The thermal events occurring during solidification process, i.e. liquidus (TL) and solidus (TSol) temperatures and the beginning of phases and eutectic nucleation, were determined with the thermal-derivative analysis and calculation of total heat of crystallisation of the analysed material.