Thermal stability and corrosion behaviour of Mg-Y-Nd and Mg-Tb-Nd alloys

The development of the microstructure in Mg-Y-Nd-Zr (commercial WE43) and Mg-Tb-Nd alloys and their thermal stability were investigated using electrical resistivity measurements and transmission electron microscopy. The mechanical properties were correlated with the microstructures developed. The creep resistance of both alloys is similar at elevated temperatures (473 K) but the minimum creep rate of WE43 at 623 K is lower than that of the Mg-Tb-Nd alloy as a result of the thermally more stable microstructure. The corrosion behaviour is one of the critical properties in the application of Mg alloys and can be generally improved by the addition of RE elements. It was shown that the corrosion characteristics of the two alloys studied differ substantially. Although the corrosion resistance of WE43 is not as good as some Mn containing Mg-RE alloys, it is much better than that of the Mg-Tb-Nd alloy with a similar total concentration of rare earth elements.