Influence of Slurry Temperature and Gate Velocity on Relative Density and Bending Strength of Relatively Thick AZ91D Plate Made by Semi-Solid Molding

Abstract

AZ91D plates of 5mm in thickness are made by semi-solid molding process, and its relative density and bending strength are investigated under various barrel temperature and gate velocity conditions. The results are as follows. In cases that the plates are made by semi-solid molding process, the relative density can be expressed as a function of the apparent Reynolds number that considers the influence of the solid fraction. At a given apparent Reynolds number, semi-solid molding process can achieve a larger relative density than conventional completely melted process; and the difference of the relative density between these two processes increases as the apparent Reynolds number increases. The bending strength increases as the apparent Reynolds number increases, however it decreases when the decrease of the relative density becomes remarkable. The difference between the maximum and the minimum bending strength of five trials at a given molding condition becomes remarkable when the apparent Reynolds number exceeds a certain value. Therefore, there exists an optimum apparent Reynolds number that can achieve a high strength stably. It is also found that a lower barrel temperature condition is required to obtain both higher relative density and greater bending strength.