The element features and criterion of formation of LPSO in magnesium alloys

The influence of alloying elements on the stacking fault energy (SFE) of magnesium alloys containing long period stacking ordered (LPSO) structure was studied systematically by means of first-principles calculation. The element features and criterion of formation of LPSO in Mg-RE-X system was discussed, when X=Zn, Cu, Ag and Cu, and RE=Gd, Dy, Ho, Er and La. It was found that stacking faults played a crucial role in formation of LPSO structure. The influence of SFE should be considered into the element features and criterion of the formation of LPSO. The element features and criterion of formation of LPSO in Mg-RE-X system were suggested to be modified as follows: the element RE and X can decrease the SFE of magnesium alloys and the algebraic expression for the sum of chemical misfit of RE and chemical misfit of X was negative with a bigger numerical value. The present results were helpful for further investigation on strengthening-toughening of magnesium alloys for LPSO was found to increase the strength and toughness of magnesium alloys effectively.