Influence of Alloying Parameters on the Structure and Properties of AK-6 Aluminium Alloy

Abstract

This work is devoted to the study of the effect of zirconium addition and crystallization rate on the structure and properties of industrial aluminium alloys. Experimental alloying of the AK6 alloy was performed. The required amount of Al-Zr-10 alloy (10 wt. % Zr) was added at a temperature of 900 °C until the zirconium content in the target alloy reached 0.1; 0.3; 0.5 wt. %. According to the results of scanning electron microscopy and X-ray diffraction analysis, the main proportion of zirconium in the initial alloy was represented by intermetallic compounds of predominantly Al3Zr composition and sizes from 5 to 50 μm. Values of microhardness measured after direct alloying of high-purity aluminum with zirconium by the electrolysis of oxide-fluoride melts demonstrate that at a zirconium content of 0.4 wt. %, the microhardness of the alloy increases by 1.5 times and continues to grow as the zirconium content increases. Based on the results of structural analysis, it was found that the average grain size of the aluminium alloy decreased by 4–5 times even at a Zr content of 0.1 wt. %. When studying the properties of the obtained samples, it was found that the addition of zirconium to the AK6 alloy does not affect its hardness, in contrast to high-purity aluminium, which is presumably due to the more pronounced influence of other components and the absence of an additive effect of zirconium on the alloy hardness. Accelerated cooling of the alloy to 103 K/s without zirconium additives has a similar effect of grain reduction, and also increases the microhardness of the alloy by 10 HB according to Brinell. A study of the combined effect of zirconium addition and accelerated cooling shows the additive effect of grinding by more than 25 times, while individual grains do not exceed 5 microns in size. The absence of intermetallic compounds in the obtained samples of the AK6 alloy after modification with the Al-Zr alloy indicates that the phase composition of the initial Al-Zr alloy does not affect the properties of the target alloys.