Rheological behaviors of the hypoeutectic A357 Al alloy: Pseudoplasticity

摘要

Effects of various thermomechanical treatments onthe microstructure and rheological behaviors of the semi-solidA357 alloy were studied using a concentric cylindrical viscometer.The size and morphology of primary solid particles duringcontinuous cooling were influenced by shear rates and coolingrates. Faster cooling rate was observed to result finermicrostructures On the other hand, at a given cooling rate,increased shear rates tend to force the primary particlesagglomerate together. At a given volume fraction solid, theviscosity of the slurry decreases with decreasing cooling rates andincreasing shear rates. The strain rate sensitivity, which is themeasure for the pseudoplastic behavior, was measured to be -1.3-1.6 within the fraction of solid range of O.45~O.65.