Improved mechanical properties of ECAPed Mg–15Al alloy through Nd addition

Abstract

This study investigated the effects of 1.5wt% Nd addition on the microstructural characteristics and tensile properties of a Mg–15Al (wt%) alloy subjected to equal channel angular pressing (ECAP). The addition of Nd was found to refine the grains of the as-cast alloy and create a more homogeneous distribution of the Mg17Al12 phase along the grain boundaries, resulting in a much thinner and more porous eutectic Mg17Al12 phase in combination with a feather-like Mg17Al12 phase and needle-like Al11Nd3 phase. During the ECAP process, these second phases are more effectively broken into small particles, reducing the recrystallized grain size through enhanced grain boundary pinning. During tensile testing at room temperature, the yield strength (222MPa) and ultimate tensile strength (321MPa) were considerably increased compared to an ECAPed, Nd-free Mg–15Al alloy (144 and 258MPa, respectively). Furthermore, at elevated temperatures of 150 and 200°C, a 19–24% improvement in strength was observed. This significant enhancement is attributed to the refined grains, an increase in the number of fine Mg17Al12 particles, and the finely dispersed distribution of thermally stable Al11Nd3 particles. Elongation is also increased by Nd addition, which is mainly due to a decrease in the amount of bulky Mg17Al12 phase known to increase the likelihood of cracking.