Molecular Dynamics Simulation Of Crack Propagation Of Al₁₂Mg₁₇

5XXX series aluminum-magnesium alloy has been widely used in aerospace,automotive,3C products and other fields because of its advantages such as high strength,good toughness,easy heat dissipation,good corrosion resistance and welding performance.However,there are a large number of second phase particles in the matrix of the aluminum-magnesium alloy.These second phase particles have an important influence on the mechanical properties,fracture toughness.In this paper,using the embedded atom method and the LAMMPS software,the molecular dynamics simulation analysis of the coarse second phase particles Al₁₂Mg₁₇in 5XXX series aluminum-magnesium alloy were carried out.In the simulation,an initial model of without strip crack and strip crack and strip crack of different length and number were established,and the same 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 potential energy change graph and stress-strain curves.In the tensile analysis of the Al₁₂Mg₁₇7 model with no strip crack along the X-axis at 300K,it is found that the stress reaches a peak of 3.85 GPa at strain is 0.175.When analyzing the existence of preformed strip cracks in the uniaxial stretching of Al₁₂Mg₁₇7 model,it is found that the initial potential energy of the system is increased due to the preformed strip crack,the tensile strength of Al₁₂Mg₁₇7 is significantly reduced,and the tensile process advances into the plastic deformation stage;And when the stress reaches the peak,the potential energy and stress of the system begin to decrease until the tension gradually becomes flat.In the simulation of the effect of different temperature on the performance of a preformed strip crack model,it is found that as the temperature increases,the potential energy of the entire system increases,and the elastic phase gradually becomes shorter,especially at a temperature of 500 K,the elastic phase hardly exists,and the entire plasticity stage elongated.Compared with 300K,the tensile strength of the model is increased at 400K and 500K.When changing the length of strip cracks,the tensile strength of Al₁₂Mg₁₇7 model with the increase of preformed strip crack length was found to decrease.The tensile strength at the preformed strip crack length of 2a₀ was 3.016Gpa and when the strip crack length was 5a₀,The tensile strength to 2.3286Gpa,And because the longer cracks have a larger contact area,they make it easier to absorb the surrounding vacancies and grow,so that the land for breaking off is faster,At this time,the corresponding potential energy curve can be illustrated the this phenomenon well.As the length of the crack grows,the tendency of the potential energy to decrease significantly becomes faster.When simulating the effect of different number of strip cracks on the performance of the Al₁₂Mg₁₇7 model,it was found that as the number of strip cracks increased,The tensile strength of the model decrease and the plastic deformability increases,and the tensile strength at a crack was 2.858 GPa.The tensile strength when the number of cracks increases to 3 is 2.350 GPa.Although the increase in the number of strip cracks increases the overall potential,it does not affect the overall trend of potential energy.