Effect of Ti Addition on the Microstructure and Mechanical Properties of Hypo-Eutectic and Eutectic Al–Si Alloys

Abstract

To study the effect of Ti–B content on the microstructure and mechanical properties of Al-7Si and Al-12.6Si alloys with Al-5Ti-1B content of 0% and 2%, respectively, were prepared through conventional melting and casting route. The microstructure and mechanical properties of as-cast alloys were investigated, and a correlation has been established between microstructural features (shape, size, and area of eutectic Si, SDAS of primary α-Al, inter-spacing between two nearby eutectic Si particles, and hardness) with strength and ductility of as-cast alloys. Results show that Ti content changes the morphology of primary α-Al grain from dendrite to rosette type in Al-7Si alloy and coarse dendrite to fine columnar dendrite in Al-12.6Si alloy. Eutectic Si particle’s shape and size also change with the addition of Ti to the melt. The thermally stable phase Al3Ti is associated with Si and forms the Ti7Al5Si14 phase. Lower SDAS values, finer dendrite α-Al grains, reduce thickness of eutectic Si particles, homogeneous structure, and minimization of casting defects in 2 wt.% Al-5Ti-1B added Al-12.6Si alloy plays a vital role in enhancing the hardness (71 HV), yield strength (YS, 126 MPa), ultimate tensile strength (UTS, 198 MPa).KeywordsAl–Si alloysGrain refinerMicrostructureMechanical properties