The effect of Ba on the microstructure and age hardening of an Mg–Zn alloy

A micro-alloying addition of Ba to Mg–2.8Zn (at.%) alloy almost doubles the hardness increment produced by artificial ageing. Alloying with Ba promotes the formation of an increased number density of the strengthening precipitates, i.e. it stimulates the precipitate nucleation, and accelerates the kinetics of precipitation during artificial and natural ageing. The solidus temperature of the Ba-containing alloy is considerably increased compared to that of the binary alloy, which allows for the use of higher solutionizing temperatures and widens the temperature range available for the mechanical processing. The dispersion strengthening in the as-homogenized Mg–Zn–Ba alloy is achieved by densely distributed intermetallic particles (Mg7Zn2Ba) present on the grain boundaries and within the grains.