Study On The Multiple Forging Process And Microstructure Evolution Of 6061 Aluminum Alloy

As a kind of high strength Aluminum Alloy,6061 Aluminum Alloy are being more and more widely used in industry,in order to improve the strength and hardness to apply to a wide variety of occasions,As far as possible to improve its mechanical properties has become the urgent needs of the current.Multi direction forging technology is a representative process of strong plastic deformation method,which can accumulate large strain to cause severe plastic deformation,so as to achieve the effect of grain refinement.As a kind of low cost and easy to realize technology,it has great development prospects.So it is very important to study the multi direction forging process of 6061 aluminum alloy for the preparation of ultrafine grained materials and the application to the real industry.Based on the study of the mechanical properties of 6061 aluminum alloy and the degree of grain refinement,in this paper,the feasibility of using finite element method to simulate the multi direction forging process and microstructure evolution of 6061 aluminum alloy is verified.The aim was to provide an effective theoretical basis and reference for the forming process parameters and optimization of ultrafine grained deformed aluminum alloy with excellent properties,and the T6 state 6061 aluminum alloy was used as the research object,hot compression and multi direction forging test were carried out,the experimental data obtained by hot compression test and draw out 6061 Aluminum Alloy 20 based on temperature and strain rate changes under the true stress-strain curve,then according to the material microstructure curve and the phase diagram,a flow stress constitutive model and dynamic recrystallization kinetics model based on JAMK theory.With the aid of DEFORM-3D software platform,the simulation and analysis of the 6061 aluminum alloy forging process were carried out.Then the microstructure evolution of aluminum alloy forging was simulated and analyzed by the method of cellular automata,And the results were compared with the microstructure dynamic recrystallization simulation results based on JAMK theory before and after multi forging experiment.Finally,the effect of multi direction forging on the mechanical properties of aluminum alloy was verified by tensile test at room temperature.Specific research results are as follows:First of all,study on the true stress-strain curve,the results show that the flow stress of 6061 aluminum alloy has a positive strain rate sensitivity under test condition.It will increase with the increase of the strain rate,and the peak stress also increases.With the increase of the deformation temperature,the trend of the decrease is obviously decreased.After this,using DEFORM-3D software to simulate the multi direction forging process of 6061 aluminum alloy,at the initial forging temperature of 300 degrees,the results show that the accumulation and distribution of equivalent strain follow the basic characteristics of hot compression deformation,with the development of the forging process,the strain distribution of the gradient increases gradually,uneven strain gradually outstanding,central region of the fastest growing in the final section forming effect of approximately annular distribution field.Because of the external and internal material forging work repeated friction,both the heat generated to make the whole Aluminum Alloy sample temperature rise,the temperature distribution showed progressively from the center to the top edge and a decreasing trend.Multi directional forging process has a significant effect on the grain size and the improvement of the material properties.In the end of the first cycle,the dynamic recrystallization has been taken place,and as time goes on recrystallization degree more and more high,the deformation of blank areas occurred fully.By the end of the forging,Most of the region has undergone dynamic recrystallization,the uniformity of the grain refinement effect is very obvious,has super fine grain state,eventually the minimum grain size has reached 0.580?m,the average grain size is about 1.79?m.Finally,the optimal forging process was determined by comparing the effects of different initial forging temperature and cycle times.At last,A two-dimensional dynamic recrystallization model based on cellular automata theory was constructed,and the dynamic recrystallization evolution of 6061 aluminum alloy during multi direction forging process was simulated and analyzed.The results show that with the increase of the effective strain and temperature rising,the original cast alloy grain boundaries in the beginning of the broken to produce a large number of fine equiaxed grain in the parent phase the new,large grain formed around a typical ring necklace structure,The original coarse grains were gradually replaced by phagocytosis,the grains were significantly refined,the dynamic recrystallization gradually tended to be slow,and the effect of grain refinement was gradually weakened.The grain size is approximately the same with the dynamic recrystallization kinetics based on JAMK theory.The microstructure of the material before and after the multi direction forging was analyzed,and the comparison with the simulation results of cellular automaton was also similar.It is verified that the cellular automaton model established in this paper can simulate and predict the dynamic recrystallization grain size distribution and evolution of 6061 aluminum alloy during multi direction forging process,And through the multiple forging process scheme can indeed microstructure of 6061 Aluminum Alloy produced significant grain refinement effect in the test,the results of tensile tests at room temperature show that the mechanical properties of aluminum alloy can be significantly improved by multi direction forging,through simulation and experimental analysis,which has important reference value and significance of ultrafine grained materials in industrial production.