Microstructure and creep behavior in AE42 magnesium die-casting alloy

The microstructural analysis of die-cast AE42 reveals a correlation between microstructure and creep strength. A lamellar-phase Al11RE3 which dominates the interdendritic microstructure of the alloy, partly decomposes above 150 degreesC into Al2RE and Al (forming Mg17Al12). The increased solubility of aluminum in magnesium at higher temperatures may also promote the decomposition of Al11RE3. The creep strength decreases sharply with these phase changes. A mechanism,for the decrease in creep strength of AE42 is proposed whereby the reduced presence of lamellar Al11RE3 and/or the presence of Mg17Al12 contribute to the observed poor creep strength at higher temperatures.