Structure-Property Correlation of Hypoeutectic Al-7.6Si Alloys with and without Al-5Ti-1B Grain Refiner
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 Alα phase. In the grain refined Al-7.6Si alloy, TiB2 is formed and these TiB2 acts as a potential site for nucleation of Alα grains. Therefore, the grain refined alloys have fine globular Alα 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.
Hardness; Fracture behaviour; Mechanical properties; Microstructure evolution; Phase analysis
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