Predicting the flow stress of high pressure die cast magnesium alloys

In the present study, we describe the characterization of three magnesium alloys, AM60, AZ91 and AE44, which were processed by high pressure die casting (HPDC) and gravity casting. Spherical microindentation was used to analyze the influence of microstructural features on the flow stress for both skin (finer grain sizes) and core (larger grain sizes and dendrites) regions of HPDC, as well as different regions of gravity step-cast plate for all three magnesium alloys. It was observed that the local yield stress and flow stress of magnesium alloys depend on grain size. The Hall-Petch slopes determined from indentation testing compared well with the results obtained from uniaxial tensile testing and literature. The Hall-Petch equation was shown to be applicable for predicting the yield strength and the flow stress at several levels of plastic strains.