First-Principles Study Of Mg-Nd-Zn Alloy Phases And Interfaces

The strengthening phase in Mg-Nd-Zn alloy determines the comprehensive mechanical properties of the alloy,and solid solution strengthening is an important strengthening means for Mg-Nd-Zn alloy.Therefore,it is important to study the strengthening phase,solid solution phase and interfacial properties of Mg-Nd-Zn alloys from an atomic perspective to understand the mechanism of the phases in Mg-Nd-Zn alloys.In this paper,the structural stability,mechan-ical properties,electronic structure and thermodynamic properties of the important strengthen-ing phases Mg1Nd1,Mg2Nd1,Mg3Nd1 and Mg12Nd1 in Mg-Nd-Zn alloys were investi-gated using a first-principles approach;the structural stability,mechanical properties,electronic structure and thermodynamic properties of the Mg12-xZnxNd4(x=3,5,7)phase formed in the Zn solid solution Mg3Nd1 alloy were calculated.Finally,the interfacial properties were calculated for the Mg(100)/MgiNd1(110),Mg(111)/Mg3Nd1(111)and Mg(110)/Mg12Nd1(110)interfaces.The following conclusions were drawn:(1)The results of the structural stability calculations for MgiNd1,Mg2Nd1,Mg3Nd1 and Mg12Nd1 show that:Mg1Nd1 has the best stability among the reinforced phases in the Mg-Nd-Zn alloy.By calculating the electronic density of states and differential charge density of the four phases,then the fundamental reason for the most stable structure of Mg1Nd1 is analyzed as Mg The calculations of mechanical properties of Mg1Nd1,Mg2Nd15 Mg3Nd1 and Mg12Nd1 show that the Mg3Nd1 phase has the highest stiffness.Finally,the calculations of thermodynamic properties show that the Mg12Nd1 phase has the best thermal stability.(2)The results of calculations on the formation heat and binding energy of the Mg12-xZnxNd4(x=3,5,7)phase formed by Zn solid solution of Mg3Nd1 show that Zn prefers to replace Mg(8c)in the Mg3Nd1 lattice and enhances the alloying ability and structural stability of the alloy with increasing Zn content.Calculations on the mechanical properties of the Mg12-xZnxNd4(x=3,5,7)phase The results show that the Mg12-xZnxNd4(x=3,5,7)phases are all brittle phases,and their stiffness and plasticity are increased to different degrees with the increase of the proportion of Zn solid solution into Mg3Nd1.The calculation of the thermomechanical properties of Mg12-xZnxNd4(x=3,5,7)phases shows that the structural thermal stability is improved when Zn solid solution into Mg3Nd1 phase and the Zn solid solution replaces the Mg(8c)position of the Mg atom,the structural thermal stability is further improved.(3)The interfacial calculations for Mg(100)/Mg1Nd1(110),Mg(111)/Mg3Nd1(111)and Mg(110)/Mg12Nd1(110)show that the adhesion work of the interfacial system is less than the fracture work,indicating that the cracks appear first at the interface.Mg(100)/Mg1Nd1(110)has the strongest interfacial stability and Mg(111)/Mg3Nd1(111)is the second and Mg(110)/Mg12Nd1(110)is the worst.