Structure-Property Correlation of Hypoeutectic Al-7.6Si Alloys with and without Al-5Ti-1B Grain Refiner

Abstract

Hypoeutectic Al-7.6Si alloy has been developed with and without Al-5Ti-1B grain refiner through the gravity casting method. Effects of 2, 4, and 6 wt % master alloy (Al-5Ti-1B) addition on the microstructural morphology, mechanical properties (percentage elongation (%El) and ultimate tensile strength (UTS)), hardness and fracture behaviour of the Al-7.6Si alloy have been investigated. Unmodified hypoeutectic Al-7.6Si alloy consists of needle and rod-like eutectic Si ((Si)_E) particles with sharp corners inside the Al_α phase. In the grain refined Al-7.6Si alloy, TiB₂ is formed and these TiB₂ acts as a potential site for nucleation of Al_α grains. Therefore, the grain refined alloys have fine globular Al_α grains and fibrous (Si)_E phase. The bulk hardness, UTS and elongation (%) are increased in the grain refined alloys. Further, fractography show that the cleavage fracture is reduced in the modified alloy and fine dimple formation is increased.