The effect of aging on mechanical properties and corrosion resistance of WE43 magnesium alloy

In the present study, the effect of aging heat treatment on mechanical properties and corrosion resistance of WE43 magnesium alloy has been investigated. The extruded billets were aged at 190, 210, and 230 °C for 4, 8, 16, 24, and 48 h after solutionizing at 525 °C for 16 h. The sample aged at 210 °C for 24 h exhibited peak hardness with the formation of oval shaped β'-precipitates with sizes around 15-20 nm as revealed by transmission electron microscopy (TEM) studies. On the other hand, aging for 48 h at the same temperature caused coarsening of β'-precipitates and formation of precipitate free zones around grain boundaries. Equilibrium precipitates of β1 and β precipitates have been detected only when aging conducted at 250 °C for 120 h. All the samples (as-received, solutionized and aged) exhibited elastic moduli between 10-17 GPa similar to that of bone. Corrosion of samples occurred by the formation of Mg(OH)2 layers because of microgalvanic (-Mg). Highest corrosion resistance was observed upon peak aging at 210 oC for 24 h. Although microgalvanic corrosion was also intensified by the precipitate/-Mg couple, the high corrosion rate was attributed to the pinning effect of fine β'-precipitates, which occurs by slowing down the growth of the Mg(OH)2/MgO layer.