Processing of T6 heat-treated Al-12Si-0.6Mg alloy

Abstract

ABSTRACTIn this study, ternary Al-12Si-0.6Mg material was manufactured by gravity die casting method in induction melting furnace. Microstructure images of alloy were taken on optical microscope after T6 heat treatment. Hardness, yield and tensile strength and breaking elongation of as-cast and heat-treated materials were measured by universal methods. CNC lathe was used for cutting tests and dynamometer was used to measure cutting force. Cutting tests were performed by using different cutting speeds-CS (450-500-550 m/min), feed rates-FR (0.05–0.15-0.25 mm/rev) and constant depth of cut-DOC (1.5 mm). Uncoated (A), CVD-TiCN + TiN (B) and PVD-TiAlN+TiN (C) coated carbide inserts were selected as a cutting tool. In the microstructural observations, it was determined that the structure of the material made up of aluminum rich α, primary and eutectic silicon, δ (Al4FeSi2) and π (Al8Mg3FeSi6) phases. The heat treatment refined the phases in the structure of the alloy. In addition, it has been determined that it improves mechanical properties (hardness, yield and tensile strength) by spheroidizing silicon particles. As a result of the cutting tests, it was detected that the cutting force (CF) reduced with T6 heat treatment at all CS and FR values. The CF, BUE (Built up edge) and BUL (Built up layer) heightened with increasing FR, while it reduced with increasing CS on all cutting tools. CF, BUE and BUL were formed at least in tools A, B and C, respectively. While continuous chip formation was detected in the as-cast part, brittle chip formation was observed in the heat-treated part due to the reduction in breaking elongation of the material.