Effect Of Torsional Deformation Behavior And Annealing Treatment On Microstructure And Properties Of 5A02 Aluminum Alloy

With the progress of modern technology,faster and faster,the development of various fields in the medical industry,for example,there are a lot of medical equipment in all need strong corrosion,high strength aluminum alloy,so many experts in the field of materials are studying how to strengthen and improve the performance of the aluminum alloy,commonly used methods are rapid prototyping,annealing process,such as mechanical polishing method for the preparation of gradient nanometer materials.Therefore,how to improve the performance of materials is the main content of this paper,this paper takes 5A02 aluminum alloy as the object of study,5A02 belongs to al-Mg aluminum alloy,is a very widely used material.This alloy has high strength,especially fatigue resistance:high plasticity and corrosion resistance,good plasticity in semi-cold work hardening,low plasticity in cold work hardening,good corrosion resistance,good weldability,poor machinability and polishable.So it is widely used in medical industry,aerospace,automotive,marine and other industrial fields.In these fields,we not only pursue the optimization of static mechanical properties,but also attach great importance to the optimization of dynamic properties.For example,the impact of high-speed impact and collision is a factor that must be considered.Therefore,based on the above background,we have done the following main work on strengthening 5A02 aluminum alloy and studying other macroscopic mechanical properties and microstructure changes:（1）In this paper,through low-temperature stress annealing,the materials are strengthened by torsion,and the original samples after annealing are subjected to different angles of torsion using a laboratory-made torsion testing machine,and materials with different grain size distribution gradients are successfully constructed.The experimental results show that the average grain size distribution in the original condition is 12.1μm,and the best gradient grain size distribution after torsional deformation ranges from 3.4μm at the edge to 3.8μm at the center,and is stretched at 0.001S^-1.The results show that the yield strength increased from 70MPa to 194MPa.With the increase of the angle of twisting turns,the average grain size decreases,the yield strength and tensile strength increase and the elongation decreases,but a good combination of strength and ductility is found,and the work hardening rate also has a increased.The hardness test shows that the gradient distribution is displayed after torsion.The hardness of edge and core increases with the number of torsion turns.After stretching,the electron back-scatter diffraction（EBSD）characterization showed that the gradient trend was weakened.（2）Although the strength of the 5A02 aluminum alloy strengthened by torsion deformation has been significantly changed,a large part of the ductility has also been sacrificed.In order to meet the better combination of strength and ductility,a annealing process after torsion is adopted.In this way,the two can have better coordination performance.After annealing at different temperatures,quasi-static uniaxial tensile test,microhardness test,and EBSD and scanning electron microscope（SEM）microscopic observation were carried out.Studies have shown that better coordination of strength and elongation can be achieved by annealing.For the unannealed sample after 8 turns of twisting,the strength of the sample after annealing at 250°C decreased from 194MPa to 182MPa,and the elongation increased from 2%to 4.5%,which is better than the performance obtained directly by twisting 4 turns.better.Judging from the combination of the statistical distribution of the microstructure and the fracture appearance is also in line with the situation.Therefore,the annealing process after torsion can improve the coordinated performance of strength and ductility.（3）High strain rate dynamic loading compression and quasi-static compression were performed on different torsion specimens and original specimens using Hopkinson compression bars and a multifunctional mechanical testing machine,the effects of different torsion angles on the mechanical properties of the same strain rate and the effects of different strain rates on the mechanical properties of materials with the same torsion angle and their strain rate effects were analyzed.At the same time,the J-C（Johnson-Cook）model was used to analyze the accuracy and predictability of the experiment,as well as the fitting analysis of whether there was a strain rate effect.