Influence of iron on the surface tension of copper

Purpose: In the paper, the results of surface tension measurements at 1473 K and 1673 K with the use of sessile drop method, concerning liquid copper-iron alloys with 0.01 to 0.05 Fe molar fractions, are presented. The aim of the study was to determine the effects of iron and temperature on the surface tension of copper. Design/methodology/approach: The experiments were conducted with the use of sessile drop method at 1473 K and 1673 K, in an argon atmosphere. For the investigations, a measuring apparatus PR-37/1600, produced by the Industrial Electronics Institute in Warsaw, was used. It consisted of a high-temperature pipe furnace, allowing the observation of a sample placed inside a horizontal reaction chamber (called a high-temperature microscope), and a camera, both coupled with a computer equipped with a program for the device work parameter control as well as for recording and analyzing pictures. The program was used for measurements of appropriate geometric parameters of liquid alloy drops which were necessary for surface tension evaluation. In order to determine the surface tension, a computational procedure, based on the least square estimation of the parameters of the differential equation system, was used, describing the shape of a sessile drop of liquid using coordinates of points placed along a curve that forms the outer contour of the drop cross-section. Findings: The experiments showed that a higher Fe content in Cu-Fe alloys led to the increase in surface tension. A temperature rise of the investigated alloys, similarly for pure metals as well as a great majority of binary and multicomponent systems, is accompanied by the decrease in surface tension. Practical implications: Surface tension has a significant impact on obtaining, refining and casting of metals and alloys. Thus, the knowledge of this parameter may be useful for both a description of phenomena that occur during these processes and their improvement. Originality/value: The presented results may be the first literature data regarding surface tension of Cu-Fe alloys with 0.01 to 0.05 Fe molar fractions.