First-Principles Calculation Of The Phase Interface Of Mg-Li-Zn-Y Alloy

Lithium alloys have excellent overall performance,such as good thermal conductivity,excellent electromagnetic shielding properties and damping properties,so they are widely used in aerospace,automotive industry,and other fields,and lithium alloys are currently one of the most valuable ultra-light metal structural materials.The Mg-Li-Zn-Y alloy has a biphasicα-Mg andβ-Li phase,which depends on the Li content,and has a ternary Mg-Zn-Y phase,which may produce quasicrystalline phase Mg₃Zn₆Y,LPSO phase Mg₁₂Zn Y,and face-centered cubic Mg₃Zn₃Y₂ phase,depending on the Zn/Y ratio content.And in the analysis of the material some people think that the effect of Mg₃Zn₃Y₂ on the properties of the material is controversial,that the non-eutectic interface between Mg₃Zn₃Y₂ and the magnesium matrix,the atoms can not form a good interfacial bond between them.And some people believe that Mg₃Zn₃Y₂has a significant enhancement effect on the properties of the material.Based on this,this paper investigates the interfacial binding properties of Mg₃Zn₃Y₂ in materials using a first-principles approach to evaluate the effect of Mg₃Zn₃Y₂ on material properties.By constructing the Mg₃Zn₃Y₂/Mg and Mg₃Zn₃Y₂/Li interfaces and calculating and analyzing the work of separation at the interface and the electronic structure at the interface,the interfacial bonding strength is investigated from the atom-to-atom bonding.The results of the calculations can provide a reliable theoretical basis for the design and development of Mg-Li-Zn-Y alloys.The main conclusions are as follows:（1）Firstly,we performed calculations for the Mg,Mg₃Zn₃Y₂ bulk phase,and the calculated results are very close to the previous experimental results and simulation results.Afterwards,the convergence of the surface was tested based on the calculation of the surface energy of Mg（0001）and Mg₃Zn₃Y₂（111）.Which at the interface is biased towards the Li element in Mg（0001）.Finally,we chose 13 layers of Mg-Mg₃Zn₃Y₂（111）,Zn-Mg₃Zn₃Y₂（111）,Y-Mg₃Zn₃Y₂（111）and 5 layers of Mg（0001）for the subsequent modeling of the Mg（0001）/Mg₃Zn₃Y₂（111）interface,and according to the different atoms at the interface terminals and the coordination of the atoms at the interface Depending on the terminal atoms of the interface and the coordination of the atoms at the interface,six types of interface models can be developed.The electronic structure of the interface shows that charge transfer does occur at the interface,while the bonded atoms at the interface are bonded to each other,and we find that charge aggregation is less around the H element in particular.（2）After that we studied the Li（110）/Mg₃Zn₃Y₂（111）interface,we performed surface convergence tests on the Li（110）surface,and we also selected a 13-layer Mg₃Zn₃Y₂（111）surface and a 5-layer Li（110）to build a sandwich model Li（110）/Mg₃Zn₃Y₂（111）interface,where Li（110）surface is biased with Mg atoms,and also the different coordination relationships between the terminal atoms of the interface and the atoms of the interface,we modeled the interface based on the classical coordination relationships,cavity,bridge and top.We found that the Li（110）surface contains a large number of Mg atoms and the maximum work of separation at the interface is 1.41 J/m2.The electronic structure analysis at the interface yields:the charge density diagram reveals that the charge transfer at the interface is relatively small.And it is found that the charge around the Li atom is very little,almost no charge is analyzed,and the whole atom presents an isolated state and cannot transfer charge with other atoms at the interface.（3）The interfacial bonding strength between Mg₃Zn₃Y₂ and the substrate was evaluated from the perspective of the charge density at the interface and the differential charge density.It is demonstrated that the effect of Mg₃Zn₃Y₂ on the properties of Mg-Li-Zn-Y alloy and the effect of the interfacial bonding of Mg₃Zn₃Y₂ on the mechanical properties of the material shows that Mg₃Zn₃Y₂ as the second phase in the analysis between the microstructure properties of the material,in the duplex Mg-Li alloy is for the enhancement of the alloy properties,the grain refinement in the interface point of view,is The grain refinement increases the contact area at the interface,which improves the bonding ability of Mg₃Zn₃Y₂ and the matrix house,which is also verified with the experimental conclusion that the grain refinement increases the ultimate tensile strength of the alloy.（4）Finally,the interfacial bonding properties of Mg₃Zn₃Y₂ are summarized.For the design of Mg-Li-Zn-Y,it is mainly hoped that the addition of Li element can improve the plasticity of the alloy,and the content of Li element is very important,while the interface between Mg₃Zn₃Y₂ and the matrix does not drag down the overall performance of the alloy.