Abstract: The influence of abrupt shearing on transient rheological behavior of semi-solid A356 alloy with different morphology of primary α-phases is explored through the use of rest time experiment by a self-designed rheometer. The morphology of primary α-phases is degenerated dendrites prepared via isothermal mechanical stirring at 141.8 s–1. Results indicate that the primaryα-phases are gradually degenerated under isothermal shearing, as a result, the apparent viscosity of semisolid A356 alloy is gradually reduce to a equilibrium state. Empirical transient rheological equations are then obtained by ways of curves fitting. The relation between parameters of the empirical equation and morphology of primaryα-phases of semisolid alloy is also gained by means of regression analysis. Results also show that the semisolid A356 alloy exhibited more notable shear thinning or pseudoplastic behavior, and expressed more prominent behavior of time dependence along with the degeneration of primary α-phases of the semisolid alloy, in other words, the semisolid alloy is possessed by obvious thixotropic behavior.

Key words: A356 alloy, Apparent viscosity, Rheological behavior, Semi-solid alloy