Tensile Behavior Of Ti₂Cu Intermetallic Compounds Studied By Molecular Dynamics Simulations

During the production and service process of Ti-Cu alloy,it is often accompanied by complex working conditions such as high temperature and high strain rate,which will cause yield phenomenon,resulting in functional failure and affecting normal use.However,current researches on Ti-Cu alloys is basically based on experimental methods.In order to study the atomic mechanism of uniform deformation of Ti-Cu alloys,the tensile behavior of Ti₂Cu intermetallic compounds was studied by molecular dynamics simulation in this thesis.The effect of temperature and strain rate on its deformation behavior was studied in combination with stress-strain curve.Since there is no embedded atomic potential for the Ti-Cu system,the original data was constructed by first principles calculations and input into a code for the development of potential functions.In order to produce samples with large variations in atomic configuration,ab initio molecular dynamics simulations were performed for Ti₂Cu structure at 300 K,500K,700 K,900 K and 1200 K.It was found that as the temperature increases,the atomic motion becomes more intense and the forces generated are larger,and different energy and force data can be obtained.The stabilized configurations at five temperatures were selected as the input for the fitting,and the atomic force,energy and stress tensor were fitted as the fitting parameters.The validity of the embedded atomic potential was further verified by testing the thermal stability of Ti₂Cu structure at different temperatures and calculating the elastic constants and lattice constants of Ti₂Cu structure.Based on the study of the above-mentioned potential functions,the mechanical behavior of Ti₂Cu at 300 K,500 K and 700 K and strain rates at 0.001/ps,0.005/ps and0.01/ps for tensile loading were simulated using molecular dynamics.It was found that the tensile process is divided into three main stages,the elastic deformation stage,the plastic deformation stage and the fracture stage.With the increase of temperature,the elastic deformation stage of Ti₂Cu structure becomes shorter,the elastic modulus decreases and the tensile strength decreases.At different strain rates,the tensile strength and plasticity of the Ti₂Cu structure gradually increase with the increase of strain rate,and the elastic deformation phase of the structure is not affected.When triaxial tensile simulations were performed on Ti₂Cu,it was found that the stress-strain curves have bimodal peaks,but the bimodal peaks disappeares with the increase of temperature.The effect of temperature on triaxial stretching is similar to that of uniaxial stretching.