Molecular Dynamics Simulation And Mechanical Properties Analysis Of Al₂Cu Under Uniaxial Tension

Aluminum and aluminum alloys are the raw materials of metal products commonly used in social production and life.Among them,7XXX series Al-Zn-Mg-Cu super hard aluminum alloy has been widely used in aerospace industry and civil transportation because of its advantages such as small specific gravity,high strength and good processability.However,in the production of 7XXX aluminum alloy,due to the influence of raw materials,processing technology,heat treatment process and other factors,there are a large number of coherent and incoherent second phase particles in the matrix.These second phase particles have important influence on the recrystallization behavior,mechanical properties,fracture toughness and corrosion resistance.In this paper,using the embedded atom method and the LAMMPS and Ovito,the molecular dynamics simulation and visualization analysis of uniaxial tension of the coarse second phase particles Al₂ Cu in 7XXX series Al-Zn-Mg-Cu super hard aluminum alloy were carried out.In the simulation,an initial model without voids and voids is established,and different conditions are imposed on the initial model under uniaxial tension.The data of atomic coordinates,temperature,pressure and stress at different time were recorded,and the tensile process under different conditions was analyzed according to the atomic orbital and stress-strain curves.The Al₂ Cu model was found to be very brittle when the 300 K was used to simulate the Al₂ Cu without the preformed void.When the strain is 0.0860,the stress reached the peak value of 6.4Gpa;However,the tensile strength and ductility of the specimens were decreased significantly when the Al₂ Cu model was introduced into the preformed voids,which the strain is 0.0498,the stress reached the peak value of 3.52 Gpa.Change the bath conditions and engineering tensile strain rate was found at 200 K to 600 K,the plastic of Al₂ Cu increases as the temperature rises,the tensile strength is decreased with the increase of temperature.However,in the range of engineering strain rate,the plastic and tensile strength increase steadily with the increase of strain rate.The analysis of atomic trajectories also revealed a value between the strain rate of 0.005 to0.01,when the tensile strain rate of Al₂ Cu exceeds this value,some of the vacancies produced by stretching are too late to take place in the system,which leads to the formation of voids in the system;And the larger voids have larger contact area whichmakes it easier to absorb the surrounding vacancy to grow,so as to suppress the growth of the surrounding small voidsIn the simulation of the uniaxial tension of Al₂ Cu containing voids,the plastic and tensile strength of Al₂ Cu decreased with the increase of the void size without changing the position of the prefabricated void.In order to study the influence of the number of voids and the pore distribution on Al₂ Cu,a 20a0×20a0×5b0 cell model was established.Changing the number of voids in the model with a radius of 1.5a0,it is found that the stress and strain curves corresponding to the number of voids coincide in the elastic deformation stage,and the plasticity and tensile strength of Al₂ Cu decrease with the increase of the number of voids.Compared with the stress and strain curves at different ages,it is found that the atomic deletion rate does not directly affect the stability of the stress-strain curve,while the size of the void is the influencing factor.The smaller the angle between the direction of the connection of the voids and the direction of the tensile,the stronger the plasticity and tensile strength of Al₂ Cu.