Design And Preparation,Modeling And Damage Simulation Of In-Situ ZrB₂/Aa6016 Nanocomposites

With the increasingly prominent energy and environmental problems,energy saving and consumption reduction has become an important direction of automobile development.Among them,vehicle body lightweight is the main way to reduce energy consumption and emissions.However,with the rapid development of the automobile industry,the performance requirements of the body materials continue to improve,the existing aluminum alloy has been unable to meet the stringent requirements of high strength,toughness,fatigue resistance and impact resistance.Therefore,in this study,the in-situ nano PRAMCs（particle reinforced aluminum matrix composite）with high strength,high modulus and high fatigue resistance are studied for structural design,performance modeling and damage failure,and the design criteria of in-situ nano PRAMCs are established to provide theoretical and technical support for the design,preparation and performance optimization of in-situ nano PRAMCs for high-performance body.In this paper,the in-situ ZrB₂/AA6016 nanocomposites are taken as the research object.From the micro and macro levels,the existing performance prediction model of the composites is improved by using the method of numerical simulation and experimental research,according to the microstructure morphology of in-situ nano PRAMCs,so that it is more suitable for the performance prediction of in-situ nano PRAMCs,to guide the structural design and preparation of the composites.Furthermore,by means of the finite element analysis of the representative volume element model,the relationship and law between the microstructure,deformation behavior and damage evolution of the composite are explored,which provides the basis for the design of the strengthening and toughening structure of in-situ nano PRAMCs.The specific content of this study includes the following four aspects:（1）In this paper,in-situ ZrB₂/AA6016 nanocomposites with 1%,2%and 3%particle volume fraction were designed and prepared,and their phase and microstructure were characterized and analyzed.The results indicate that the grain size of the composite decreases continuously with particle volume fraction increasing.The average grain size of the composite decreases from 58.7μm to 52.9μm,35.1μm and22.9μm.Most of the particles exist in the form of agglomeration in the composite,most of the ZrB₂ particles are polygonal,the number of particle edges is between 4 and 6.The diameter of 90%ZrB₂ particles are between 30 nm and 90 nm,and the average diameter is about 61 nm.（2）Based on Eshelby’s equivalent inclusion theory,the in-situ ZrB₂/AA6016nanocomposite is used as model material.Meanwhile,the volume fraction,particle shape and the characteristic parameters of the interface are integrated into the model,and the influence factors of the interface structure are introduced to establish a new model of in-situ nano PRAMCs which can effectively predict the elastic modulus.The predicted value of the new model is more consistent with the measured value,and the absolute deviation value is less than 3%,which provides theoretical guidance for the accurate prediction and design of the elastic modulus of in-situ nano PRAMCs.（3）Based on the linear superposition method,four strengthening mechanisms including fine grain strengthening,CTE strengthening,Orowan strengthening and particle loading strengthening are considered synthetically to predict the yield strength of in-situ nano PRAMCs with different particle volume fraction,and the influence factors of particle distribution are introduced to optimize the Orowan strengthening model and CTE strengthening model,so that the yield strength prediction model is more consistent with the experimental value,and the deviation value is not high More than5%.Thus,the corrected yield strength prediction model can reflect the relationship between the structure and properties of in-situ nano PRAMCs more truly.（4）A representative volume element model of composites was established to simulate the deformation and damage failure of in-situ nano PRAMCs.In order to analyze the influence of particle agglomeration on the damage evolution and deformation process,the composite finite element models with local particle volume fraction of 15%,20%and 25%were established respectively,and the continuous displacement load was applied to simulate the damage evolution of the composite.The results show that the damage of materials mostly starts near the particle interface,and mostly lies at the sharp corner of particles.With the increase of loading,the damage gradually extends to the whole model matrix,resulting in failure fracture of the model.It is found that the higher the agglomeration degree is,the lower the elongation of the composite is under the same particle volume fraction,and the higher the particle volume fraction is,the earlier the fracture will be.