Effect of Pb and Sb additions on the precipitation kinetics of AZ91 magnesium alloy

Effect of Pb and Sb additions on the precipitation sequence and ageing kinetics of AZ91 alloy has been studied using the differential thermal analyzer, optical microscopy and scanning electron microscopy. The precipitation sequence in the AZ91 alloy is not altered whereas the enthalpy required for dissolution of β phases changes with respect to the individual additions of Pb and Sb. The quantitative analysis of activation energy calculated from the DTA results using Kissinger method demonstrates the activation energy required for the Mg17Al12 phase formation is decreased from 5.21 to 3.5821 kJ/mol with Pb addition whereas it is increased from 5.21 to 8.37 kJ/mol with Sb and these results are correlated with the ageing characteristics.