PLC Effect And Cyclic Plastic Deformation Mechanism Of Al-Mg Alloy By Molecular Dynamics Simulation

Al-Mg alloy is a kind of Al alloy with Mg as the main alloy element.Because of its good comprehensive mechanical properties,it is widely used in industry and belongs to a relatively mature Al alloy series.With the development of manufacturing technology,micro and nano scale metal materials are used more and more.Micro and nano scale metal materials have many properties that conventional materials do not have,and their mechanical properties are significantly different.Micro and nano materials are often subjected to cyclic loading in the process of manufacturing and using.Many researches are mainly based on traditional analysis methods,and the results can not accurately describe the micro deformation characteristics of materials.Therefore,it is of great significance to study the deformation mechanism and mechanical behavior of Nano Al Mg alloy under cyclic loading.Based on the principle of molecular dynamics,this paper studies the plastic deformation mechanism of Al-Mg alloy under uniaxial tensile loading,the physical deformation law of materials in different deformation stages during uniaxial tensile deformation,and the plastic instability phenomenon in Al-Mg alloy,i.e.portevin Le Chatelier(PLC)effect,through comparative tensile test.The effect of Mg atoms on dislocation is the main mechanism of PLC effect.In the process of plastic deformation,due to the interaction between solute atoms and dislocations,some solutes gather in the area with high dislocation density,resulting in dislocation packing,dislocation clusters,dislocation tangles and other structures.Cyclic loading increases the number of defects in the material,blocks the dislocation slip movement caused by plastic deformation,forms dislocation lock and other obstacles,and causes hardening of the material.As the number of cycles increases,or the single strain becomes larger,the defects caused by the accumulated strain of the material cause the dislocation to start and cause the material to soften.The mechanism of plastic deformation during cyclic loading of polycrystalline model is analyzed and compared with the results of single crystal simulation.The dislocation barriers in polycrystalline grains are still the important factors that cause the increase of the strength in the grains.There are Hall-Petch relationship and anti Hall-Petch relationship among the models with different grain sizes.After cyclic loading,the grain boundary distribution tends to the direction of maximum shear stress.The aggregation of solute atoms in the grain boundary is also one of the reasons for the hardening of polycrystals.The content of solute atoms in the grain boundary of polycrystals is significantly higher than that in the crystal,which results in the strengthening of the grain boundary.