Grain Refinement Efficiency by Shearing Above and Below the Liquidus
Haghayeghi, P.Kapranos, “Grain Refinement Efficiency by Shearing Above and Below the Liquidus”, Solid state phenomena, Vol.217-218, 2015, PP.23-28.
There is a debate whether grain refinement is more effective when shearing above or below the liquidus. In this work, examination of the microstructural evolution in AA7075 alloy has been performed, after stirring above & below the liquidus the results suggest that shearing above the liquidus is more effective. The outcomes indicate that at temperatures below the liquidus, the convective forces produced by electromagnetic forces cannot break the dendrites due to low velocities, whilst at shearing above the liquidus through a cavitation-enhanced nucleation mechanism grain refinement is promoted. It appears that by applying magnetic forces above the liquidus temperature, shearing effects result in finer grain sizes and consequent enhancement of properties.