Study On Atom Packing Changes Of TiAl Alloy Nanoparticles By Molecular Dynamics Calculations

y-TiAl alloy has a range of application in the aerospace and automotive fields because of its excellent properties.At present,people widely used techniques such as powder metallurgy to manufacture alloy components in the industry.During this process,TiAl alloy nanoparticles as raw materials,its thermal stability and microstructure change in the sintering process have an important influence on the microstructure and properties of product.Thus it is important to study the atom packing stabilityof the alloy particles.In this paper,we construct TiAl nanoparticles and the system containing two TiAl nanoparticles and perform molecular dynamics calculations based on embedded atomic potential model(EAM).By calculating the average energy,the pair distribution function(PDF),pair analysis for these particles and atomic packing,the results are obtained as the following:1.The structural change of the nano-alloy particles starts from the position changes of the surface atoms,and the changes occur in a wide temperature range.Above a high temperature,the structural changes of the alloy particles appear from the orderly packing to disordered state.As the particle size increases,melting temperatures of these particles approaches to the melting point of alloy bulk.At lower temperature,the stability of the atom packing inside one large particles is obviously higher than that of one small particle.When the temperature is high,the surface of the particles has a variety of defects such as atomic row misplacement,vacancy or interstitial atoms.During the process of heating,the shapes of these nanoparticles change from quasi-sphere to irregular polyhedron.2.In the system of two nano-alloy particles,the two particles are merged at room temperature,and there is a connecting region between them.Some defects such as atomic row misplacement exist in this region,and there is a tilting angle between the two particles.With the increase of the temperature,the connecting region becomes wide or lengthen accompanying with the diffusion of the atoms.In the meantime,the angle disappears,and the atom packing presents the features of the ?-TiAl.In the high temperature range,which is below the melting point,there exists sliding of the two particles.The structure changes of the region,being away from the connecting region,of the particle are similar to those of one single particle.When the particle size is small,the temperature of the structural change in the connection region is low.The interval and contact facets also affect the atom packing in the connection regions.