Nucleation mechanism of Mg17Al12-precipitates in binary Mg–7 wt.% Al alloy

We show that the classical nucleation theory that describes the critical nucleus as a coherent pill-box fits the experimentally measured nucleation rate of Mg17Al12-precipitates in undeformed Mg–7 wt.% Al alloy much more accurately than the classical theory that describes the critical nucleus as an incoherent sphere. The nucleation of Mg17Al12-precipitates takes place in the transient nucleation regime. Coarsening of the Mg17Al12-precipitates occurs just before the steady state nucleation rate is reached.

► The evolution of precipitation in a binary Mg–Al alloy is demonstrated by scanning electron microscopy images. ► The nucleation kinetics are determined by application of the classical nucleation theory. ► The shape and surface energy of the nucleus is determined from the experimental results.