The Effect of Comodification by Scandium and Zirconum of Alunium Alloys of the Al-Mg-Cu System on the Casting Properties

Processy litʹâ, 2020, Tom 141, №3, p.19-26

Abstract

Received 15.07.2020

UDC 669.018.28:546.631:546.831

The joint effect of scandium and zirconium additives on the interfacial interaction and fluidity of AlMg-Cu system melts, similar in composition to those used as filler materials for wrought aluminum alloys, is investigated. The structure formation of various zones of the welding joints occurs via nonequilibrium conditions. The cooling rate of the weld metal varies widely depending on welding method and mode. The short term welding heatings lead to special structural transformations in the heat-affected zone, causes softening of the base metal and a decrease in its mechanical properties. One of the main ways to solve the problem of softening during thermal stresses in the process of aluminum alloys joining is to modify their structure with scandium and zirconium. At the same time, the influence of these modifiers on the characteristics of the melt and in particular the casting properties of aluminum alloy systems containing copper and magnesium has not been studied enough, and the available information is contradictory. The fluidity is the ability of the melt to spread and evenly fill the space at the junction of two surfaces during welding, so it is an important technological characteristic that allows one to form the body of the weld without shells voids and other defects.The effect of scandium and zirconium modification in an amount up to 0,75 wt. % on fluidity, linear shrinkage, and crack resistance was investigated. It was shown that the overall increase in the heat of crystallization associated with the formation of new phases as a result of modification is the main factor in increasing the fluidity of the melt, regardless of the increase in its viscosity, due to the appearance of dispersed inclusions of nuclei in the liquid. A significant increase in crack resistance during co-modification with scandium and zirconium is associated with the distribution of shrinkage of the casting and the number of inclusions of the primary intermetallic phases with under eutectic amounts of the modifier.