Influence of temperature-induced changes in Al – Si system melt structure on structure and electrical resistance of alloy in solid state

Abstract

According to the results of previous studies, it was found that the temperature dependence of electrical resistance during heating of the Al + 17,6 % Si melt curve characterized by presence of several sharp inflections. This gave grounds for asserting possibility of temperature-induced changes in structure of specified system melts. However, it remains an open question whether the changes that occurred when melt was overheated are preserved during subsequent cooling. The problem of effect of temperature-induced changes in Al–Si melts structure on the structure and properties of the alloy in the solid state also requires a more detailed study. Resistometric studies of melt were carried out according to the method [1]. The ability to preserve temperature-induced changes in melt was assessed by electrical resistance value during cooling of the overheated Al + 17,6 % Si melt at five characteristic temperature values. To avoid errors cozied by imbalance, only results obtained after stabilization of melt resistance at a given temperature were taken into account. Temperature-induced changes in melt structure were evaluated by structure of solid samples obtained by quenching from the liquid state. The nature of influence of changes that occur when the melt is overheated on solid alloy structure and properties was determined by specific electrical resistance values and material microstructures of samples obtained after melt isothermal holding at temperatures of 720 °C, 880 °C, 960 °C and 1050 °C. The presence of electric resistance significant hysteresis can indicate that the changes that occurred during melt overheating are preserved during its cooling. It was also established that the specified changes affect to properties (in particular, specific electrical resistance) and the microstructure of the solid alloy (first of all, the melt overheating affects to size of primary silicon particles). Keywords: aluminum, silicon, thermodynamic equilibrium, melts, electrical resistance.