Longauerová M., Grutková J., Grígerová T., Beháň B.
METALLOGRAPHY OF AG-CU ALLOYS
Abstract
The aim of this work is to investigate the effect of casting method and chemical composition on the structure and casting defects of alloys AgCu25 with varying content of Fe. The chemical compositions of these alloys are listed in Table 1 in weight percent. The alloys were cast into a metallic mould as well as a sand mould. Ingots 15 mm thick, 90 mm wide and 200 mm long were obtained. The casting temperatures were: 1050-1080°C (alloy No.1), 950°C (alloy No.2). The metallographic samples were prepared by the usual method and etched by solution with NH4OH and H2O2. It was found that the structure is dendritic composed of a white phase enriched by Ag and of lamellar eutecticum, which consists of a white phase with high content of Ag and of dark fine lamellas of Cu-rich solid solution. Identification of the structure phases in similar alloy was confirmed in our earlier paper [3]. The cast structure showed low directionality of the dendritic axis in both alloys. The dendritic structure after casting into the metallic mould is finer than after casting into the sand mould, which is the result of more rapid cooling and higher Fe concentration. There is an eight times greater number of dendrites to the area unit after casting into the metallic mould than into the sand mould. It seems that the larger number of dispersive particles in alloy No.2 cast into the metallic mould is also a result of higher Fe content in this alloy. Distinct verification of this however requires additional detailed analysis. Similarly, there are more casting defects such as large blowholes after casting into the metallic mould than into the sand mould, due to more rapid cooling and lower casting temperature.
Editors and press
AMS online
