Effect of Pb addition on ageing behavior of AZ91 magnesium alloy

The ageing behavior of AZ91 alloy containing 2 wt.% lead is investigated. The results show that addition of Pb suppresses the discontinuous precipitation and thereby slows down the ageing kinetics. Even though the peak hardness obtained for both alloys is almost same, the peak hardness reaches after 2400 min for Pb added alloy against 900 min for the base alloy. The presence of Pb in solid solution might have inhibited the diffusion of Al and Mg atoms, which is essential for the formation, and growth of discontinuous precipitation in this alloy.