Research On Microstructure Evolution Behavior Of 304 Austenitic Stainless Steel During Cold Drawing And Annealing

In this paper,the microstructure evolution and mechanical property changes during the cold drawing of 304 austenitic stainless steel,as well as the effects of deformation,annealing temperature and annealing time on the recrystallization structure change and texture evolution during annealing were studied systematically by EBSD,TEM,XRD,OM,microhardness and other material characterization methods.The main conclusions are as follows:First,the microstructure and mechanical properties of 304 austenitic stainless steel during the cold drawing process were analyzed by EBSD,TEM,XRD,OM,micro hardness and other material characterization methods.As a result,it was found that as the amount of deformation increased during the drawing deformation,the crystal grains were drawn into fibrous shape along the drawing direction,and the surface and the center were deformed unevenly.As the amount of deformation increases,the content of deformationinduced martensite increases,but the distribution of deformation-induced martensite is not uniform,with the highest content in the central area and the lowest in the surface area.Through EDS spectrum analysis,it was found that the distribution of elements in the three different areas of the longitudinal section of the steel wire sample with different deformations was the same,there was no obvious element segregation along the edge of the steel wire sample to the center.As the amount of deformation increases,the tensile strength of the sample increases and the plasticity decreases.Under the condition of the same amount of deformation,the hardness value on the cross section of the steel wire gradually increases from the surface to the core in the radial directionSubsequently,samples with different deformations were annealed at 700 ?-800 ?for different time.Through EBSD analysis,it is found that when the annealing temperature is relatively low,the amount of deformation is the main factor affecting recrystallization,because the annealing temperature is low,and the driving force for recrystallization nucleation and growth is relatively small.The recrystallized nucleus is always formed at the maximum distortion caused by plastic deformation,and it can only grow into a recrystallized nucleus by consuming the surrounding high energy region.As the degree of deformation increases,more high-energy regions will be generated,which will facilitate the formation of recrystallized nuclei.When the annealing temperature is increased to 750 ?,the critical nucleation size is reduced,and most of the deformed regions can meet the storage energy requirements of the recrystallization nucleation.Therefore,the effect of deformation on the recrystallization gradually decreases.When the annealing temperature reaches 800 ?,the high temperature can greatly reduce the critical nucleation size,the amount of deformation to promote recrystallization is lower than the annealing temperature,and the deformation matrix is mostly replaced by recrystallized grains.With the increase of annealing temperature,the extension of annealing time and the decrease of deformation,the recrystallized grain size has a certain degree of increase.A flaky {111} annealed twin structure was found during the recrystallization process,and the annealed twin volume fraction increased with the extension of the holding time and the amount of deformation.During the annealing process,the texture of <111>//DD and <100>//DD coexisted in the deformed structure;At the same annealing time,the <111> texture strength of the sample with a deformation of 33% gradually decreases with increasing annealing temperature,but the <111> texture strength of samples with 77% deformation increases gradually with the increase of annealing temperature;Under the same annealing temperature and annealing time,as the amount of deformation increases,the texture strength of <111> gradually increases.Through the analysis of the hardness value after annealing,it is found that the hardness value of the steel wire decreases with the increase of the annealing temperature and the extension of the annealing time.When the annealing temperature is relatively low,the recovery softening effect reduces the hardness value.As the amount of deformation increases,the fine grain strengthening effect increases the hardness value.Therefore,as the amount of deformation increases,the hardness value will decrease first and then increase.When the annealing temperature is increased to 800 ?,the fine grain strengthening effect makes the hardness value of the steel wire increase with the increase of the deformation.