Effect of TiB2 and Al3Ti on the microstructure, mechanical properties and fracture behaviour of near eutectic Al-12.6Si alloy

A near eutectic Al-12.6Si alloy was developed with 0.0wt%, 2.0wt%, 4.0wt%, and 6.0wt% Al-5Ti-1B master alloy. The microstructural morphology, hardness, tensile strength, elongation, and fracture behaviour of the alloys were studied. The unmodified Al-12.6Si alloy has an irregular needle and plate-like eutectic silicon (E-Si) and coarse polygonal primary silicon (P-Si) particles in the matrix-like alpha-Al phase. The P-Si, E-Si, and alpha-Al morphology and volume fraction were changed due to the addition of the Al-5Ti-1B master alloy. The hardness, UTS, and elongation improved due to the microstructural modification. Nano-sized in-situ Al3Ti particles and ex-situ TiB2 particles caused the microstructural modification. The fracture images of the developed alloys exhibit a ductile and brittle mode of fracture at the same time. The Al alpha 5Ti alpha 1B modified alloys have a more ductile mode of fracture and more dimples compared to the unmodified alloy.