The aim of this paper was to attain defect free, pure copper castings with the highest possible electrical conductivity. In this connection, the effect of magnesium additives on the structure, the degree of undercooling (ΔTα = Tα-Tmin, where Tα – the equilibrium solidification temperature, Tmin – the minimum temperature at the beginning of solidification), electrical conductivity, and the oxygen concentration of pure copper castings have been studied. The two magnesium doses have been investigated; namely 0.1 wt.% and 0.2 wt.%. A thermal analysis was performed (using a type-S thermocouple) to determine the cooling curves. The degree of undercooling and recalescence were determined from the cooling and solidification curves, whereas the macrostructure characteristics were conducted based on a metallographic examination. It has been shown that the reaction of Mg causes solidification to transform from exogenous to endogenous. Finally, the results of electrical conductivity have been shown as well as the oxygen concentration for the used Mg additives.
The present research was conducted on thin-walled castings with 5 mm wall thicknesses. This study addresses the effect of the influence of
different master alloys, namely: (1) Al-5%Ti-1%B, (2) Al-5%Ti and (3) Al-3%B, respectively on the structure and the degree of
undercooling (ΔTα = Tα-Tmin, where Tα - the equilibrium solidification temperature, Tmin - the minimum temperature at the beginning of
α(Al) solidification) of an Al-Cu alloy. The process of fading has been investigated at different times spent on the refinement treatment ie.
from 3, 20, 45 and 90 minutes respectively, from the dissolution of master alloys. A thermal analysis was performed (using a type-S
thermocouple) to determine cooling curves. The degree of undercooling and recalescence were determined from cooling and solidification
curves, whereas macrostructure characteristics were conducted based on a metallographic examination. The fading effect of the refinement
of the primary structure is accompanied by a significant change in the number (dimension) of primary grains, which is strongly correlated
to solidification parameters, determined by thermal analysis. In addition to that, the analysis of grain refinement stability has been shown
with relation to different grain refinements and initial titanium concentration in Al-Cu base alloy. Finally, it has been shown that the
refinement process of the primary structure is unstable and requires strict metallurgical control.