Investigation of optimum process parameter of lost foam casting of A356/SiC metal matrix composite

Abstract

Metal Matrix Composites (MMCs) are unceasingly substituting engineering materials because of its high stiffness and strength over homogeneous materials formulation. It has been utilized in engineering structural applications like aerospace, automotive and defense. In industries MMCs are mostly fabricated by squeeze casting, stir casting, infiltration technique, and spray deposition technique. In these processes, there are some limitations like difficulties in producing intricate shapes, homogeneous distribution of ceramic particles and poor wetting property between reinforcement and matrix alloy etc. To overcome these limitations, Lost Foam Casting (LFC) is used to fabricate MMCs. In this investigation an attempt has been made to produce intricate castings of (A356 Al alloy-SiC) particulate type Metal Matrix Composites using LFC process. The rectangular expanded polystyrene (EPS) patterns are used in this LFC process instead of circular patterns. The LFC process quality is strongly affected by the elimination of degradation product which in turn depends on the process parameters such as sand grain size, coating grain size, pouring temperature and coating method. These four process parameters with three levels are considered for Taguchi’s technique with L9 Orthogonal Array (OA) and the experiments were conducted. Density and tensile strength of the castings are considered as quality characteristics of the LFC process. From the ANOVA results, it reveals that the sand grain size and coating grain size mainly influence the casting quality. The optimal process parameters are sand grain size of AFS 50, coating grain size of 212 µm, pouring temperature 800 °C and coating method of brushing technique.