Elastic properties of long periodic stacking ordered phases in Mg-Gd-Al alloys: A first-principles study

Long periodic stacking ordered (LPSO) phases have been reported to enhance the strength and ductility of Mg alloys due to their high elastic properties. In the present work, the effects of atomic arrangements in terms of Gd-Al L1(2)-type clusters on LPSOs' elastic properties in the Mg-Gd-Al system were studied using first-principles calculations. Four types of LPSO phases (10H, 18R, 14H, and 24R) were investigated with and without an interstitial atom in the center of the L1(2)-type clusters. It was observed that the elastic stiffness components of the LPSO phases such as C-11, C-33 and C-66 are closely related to the bonding distances of L1(2) cluster. Furthermore, the interstitial atom within the L12 cluster plays an important role in affecting the elastic stiffness constants of LPSOs, resulting in an increase of C-11 and C-33 due to the bonding distances of L1(2) cluster.