First-principles study of generalized-stacking-fault (GSF) energy in Mg with Al and Zn alloyings

• Published in: Journal of alloys and compounds 2013-10, Vol.575, p.423-433
• Main Authors: Wang, Cheng, Wang, Hui-Yuan, Zhang, Hua-Yuan, Nan, Xiao-Long, Xue, En-Song, Jiang, Qi-Chuan
• Format: Article
• Language: English
• Subjects: Alloys; Aluminum; Computer simulations; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Electron states; Electronic properties; Exact sciences and technology; Magnesium; Magnesium base alloys; Mechanical and acoustical properties; Mechanical and acoustical properties of condensed matter; Mechanical properties; Metals and alloys; Methods of electronic structure calculations; Physical properties of thin films, nonelectronic; Physics; Slip; Stacking fault energy; Stacking faults; Stacking faults and other planar or extended defects; Structure of solids and liquids; crystallography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Zinc
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.05.187

•As Al or Zn contents increase, GSF energies of Mg-Al-Zn solid solution decrease.•As Al or Zn contents increase, more locations with low GSF energy emerge.•Al and Zn dopings decrease GSF energy by softening Mg–Mg of slip planes.•Reduced GSF energy promotes activation of non-basal slip and enhances plasticity.•Criterion for predicting the most probable location for planar defect is proposed. Influences of Al and Zn contents on the GSF energies in Mg–Al–Zn alloys (Mg141Al2Zn1, Mg139Al4Zn1 and Mg135Al8Zn1; Mg142Al1Zn1 and Mg141Al1Zn2) are investigated by the first-principle methods. With an increase in Al or Zn contents, the unstable stacking fault energy (γus) continuously decreases and more slip positions with a low γus emerge in the Mg matrix for the {0001}〈112¯0〉,{101¯0}〈112¯0〉,{101¯1}〈112¯0〉 and {112¯2}〈112¯3〉 slip systems, which both facilitate the formation of basal , prismatic , pyramidal and stacking faults. More importantly, a criterion for predicting the location with the highest probability to form stacking faults in different slip systems is proposed, which contributes to predicting the ductility of Mg alloys on the atomic scale. The decrease in GSF energies with Al and Zn additions is presumably attributed to the enhanced charge flow and the weakened Mg–Mg bonds on slip planes.