Influence of Annealing of Al-5Ti-1B Master Alloy on Hot Tearing of Cast Al-7Si-3Cu Alloy

Abstract

Hot tearing is a common and severe defect encountered in aluminium alloys castings. It is affected by alloy composition as well as processing conditions and variables. In Al–7Si-3Cu presence of copper increases mechanical properties of the alloy, but it makes the alloy susceptible to hot tearing. The observations on the microstructures and the fracture surfaces propose that the hot tearing initiated at the grain boundaries and propagated along them through the thin liquid film. Grain refinement limits the hot tearing tendency of the Al-Si-Cu alloy. An attempt has been made to record the effect of annealed Al-5Ti-1B master alloy on minimizing hot tearing tendency in the gravity die cast of Al-7Si-3Cu alloys. It is observed that grain refining efficiency of Al-5Ti-1B master alloy is increased with increase in annealing temperature. This is attributed to the increased fraction of TiAl3 particles and the possible formation of (Ti,Al)B2 phase. Characterization study has been carried out by OM, SEM and XRD analysis.