Understanding texture domains and relations between pre-eutectic and eutectic phase during Al-Si alloy solidification

Abstract

Phase morphology and crystallographic texture are important components of a solidification microstructure. Probability of nucleation of a nucleus is a strong function of local chemical & thermal conditions and its atomic orientation. Similarly, the growth kinetics for various crystal planes is dependent on its crystal orientation apart from local environmental conditions. The combined effects of nucleation & growth kinetics along with solidification conditions dictate the resulting microstructure of an alloy. In this study, various phases of a near eutectic Al-Si alloy are examined by serial sectioning and 3D reconstruction. A peculiar microstructure is observed in which primary silicon is present in the immediate proximity of primary aluminum. Observations through electron back scatter diffraction show that the microtexture of primary and eutectic Si is similar (with in a twin relation) and thus it is concluded that the formation of eutectic starts with eutectic Si forming on the primary Si.

Influence of cryorolling on microstructure and mechanical properties of a cast hypoeutectic Al–Si alloy

“…Al-Si cast alloys are extensively used in automobile, aerospace and various other general engineering applications due to their high strength to weight ratio, excellent castability, low thermal coefficient, high corrosion resistance and good wear resistance [1][2][3][4][5]. However, these alloys often possess low strength, insufficient ductility and poor machinability due to the presence of large, irregularly shaped and unevenly distributed hard & brittle silicon containing eutectic particles [6].…”