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

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.