Influence of Copper Chills and Pouring Temperature on Mechanical Properties of LM6 Castings

Aluminum silicon alloy castings are highly used in automobile industries due to their excellent casting and machining ability, corrosion resistance and high strength-to-weight ratio. The mechanical properties of aluminum–silicon LM6 alloy are mostly dependent on solidification and casting parameters. This paper presents an experimental investigation made on aluminum–silicon (Al–Si) cast LM6 alloy using sand casting process. The main objective of the research is to investigate the effect of chill thickness and pouring temperature on LM6 sand castings. The casting parameters such as pouring temperature and external copper chills are considered for the experimental work. The simulation work has been carried out with AutoCast-X1 software for obtaining appropriate design parameters. The experimental work has been carried out in the foundry. The pouring temperatures 730, 750 and 770 °C are considered for experiments along with varying chill thickness. The use of end chills during casting not only favors directional solidification but also enhances solidification. Rapid cooling rate helps to get finer structures and improved mechanical properties. In this work, an attempt has been made to obtain the better cooling rate of LM6 castings using copper chills. The mechanical properties such as hardness and ultimate tensile strength (UTS) are analyzed. It is seen that the external chill has a significant influence on the properties of the casting components. The design of experiment has been set up and experiments were conducted as per full factorial array. Castings are made under the constraint of the process and methodical parameters at three different levels. The mathematical models of UTS and hardness have been developed. The micrographs of microstructure of castings with and without applications of copper chills have been compared using optical microscopy. The better mechanical properties such as UTS and hardness were obtained by proper combination of pouring temperature and application of external copper chills.