Some considerations on the turning of aluminum-manganese cast alloys

Abstract

Solubility of manganese in aluminum decreases with the drop in temperature; for example, it is 1.82% at eutectic point of 685°C, and 0.36% at 500°C. However, it is known to be independent of the effects of heat treatment. It is expected that the addition of manganese, having low solubility in aluminum, will improve machinability, since the addition of lead, which is insoluble in aluminum, improves machinability of wrought aluminum alloy such as 11S. In these studies, 3 sorts of aluminum-manganese alloy castings were produced, according to Mn content in the range of 1.5-5.5% for conducting turning tests. The relation between Mn content and machinability was examined by the observation of cutting resistance, roughness of surface, built-up edge, chip treatment, etc. The results obtained were as follows. Cutting resistance was much lower than that of pure aluminum at the addition of 1.5% of Mn, but gradually decreased with the higher content of Mn. However, surface roughness was more deteriorated and the growth of built-up edge was more active when Mn content was higher than 1.5%. Accordingly, satisfactory effects of higher contents of Mn were not observed in the results of machinability, even when mixed phase of α+β of Mn was contained in the alloy.