Investigation of the Effect of Ceramic Shell Thickness on Mechanical and Metallurgical Microstructure of Aluminum Alloy A3 5 6 in Investment Casting

Casting process is an important process for fabricating industrial parts that dates back to 4000 B.C., i.e., when man used this method for the production of jewelry, spearhead made of copper, and other tools that the process has rapidly developed in recent years. Casting process is classified to various types, such as die-casting, centrifugal casting, sand casting, permanent mold casting, and investment casting. Generally, the casting process is feeding molten metal into the cavity of the desired shape in a mold, followed by cooling of the molten and solid physical production. However, the main difference between these processes is different procedures for making a mold. In this thesis, regarding the importance of investment casting in producing complex parts with high dimensional accuracy, this process was investigated. Firstly, the aim of the project was thorough introduction of investment casting, design and construction of pattern, and production of a part by casting using various shell thickness parameters. The aim of this study was to investigate the microstructure, mechanical and metallurgical properties of aluminum A356 in investment casting. In this research, the sample was designed in CATIA software with two different shell thicknesses and the investment casting process was simulated by Pro Cast. The simulation showed that the more the thickness of the ceramic shell is, the mold cavity is filled at a slower rate. After mechanical tests on samples, the results showed that the part which has been produced in the ceramic mold with higher thickness has more internal defects, because the high thickness of ceramic shell does not allow gases to exit through the pores of the ceramic mold. The trapped air causes the mold cavity. Therefore, it was concluded that in order to produce higher-quality parts, the minimum thickness of the ceramic shell should be used. However, it should not be considered to the extent that doesn't have sufficient resistance against heat.