Study On The Influence Of Adding Elements On Interfacial Features Of W-Cu System

The W-Cu based alloys are widely used in aerospace,electronic information,defense industry,electrical engineering,mechanical processing and other fields because of their excellent mechanical properties and functional characteristics.The addition of certain solute elements can further improve the comprehensive performance of W-Cu alloys.However,in the multiphase system of W-Cu composites,there is a complicated relationship between the solute elements and the different phases and interfaces.At present,it lacks mechanisms for the relationship and guidance for rules of materials design,which leads to difficulties to obtain the solute elements selection strategy and composition design method,and greatly limits development of new type highperformance W-Cu material systems.Therefore,it is of great significance to study the interface characteristics and solute optimization method of W-Cu system,to analyze the mechanisms of solute concentration effect on interface stability and mechanical stability,and to predict the optimal concentration range of solute elements,for the design and development of high-performance W-Cu based alloy materials.In this work,based on the first principles calculation,the solute and grain boundary models of W phase,Cu phase and W/Cu phase boundary were constructed to study the interface characteristics and solute optimization,and the interactions between solute elements and different-phases and interfaces in the W-Cu system.Combining with the calculation of the segregation energy and electronic structure,the differences and microscopic mechanisms of the segregating of solute elements at the phase and grain boundaries in the W-Cu system were revealed.The correlation between the strongly segregating elements and the interface stability was elucidated by comparing the results of added solute elements in the W-Y and W-Sc systems.Furthermore,the basic criterion for selecting solute elements in W-Cu composite system was proposed based on combining calculations of the formation energy of Cu-based solid solution with segregation energies at phase and grain boundaries.Based on the first principles calculation,using the W-Y system as an example,the interface segregation model considering solute concentration effect and multilayer segregation was for the first time constructed to study the effect of solute concentration on the dispersion of solute atoms in the region of interface and on the second phase precipitation in the solid solution.The mechanism for the W-Y bond transformation from the antibonding in the grain interior to the bonding at the grain boundary was elucidated.The relationship of the segregation energy changing with the solute concentration was obtained.The trends of monolayer and multilayer segregation at different solute concentrations were predicted.Furthermore,the mechanism of the stability weakening of the interfacial phase induced by the segregation of Y in the W-Y system was clarified.The optimal solute concentration range and also the solute concentration range that should be avoided in the W-Y system were proposed,with the consideration of the mechanical properties and the interface stability.The studies provided reliable guide for the composition design of high-performance W-Cu based alloys and a new theoretical analysis method.