Mechanical Properties And Micro-deformation Mechanisms Of 2205 Duplex Stainless Steel Under Cold Rolling

Compared with plastic working at high temperature,the deformation conditions of the material during cold working and the evolution mechanism of new grains have not been well developed.The processing properties of the material,its phase composition and the deformation method have an impact on the final grain size.And the kinetics of grain refinement has not been studied in detail.The reason is mainly because the severe plastic deformation processes such as equal channel radial angular extrusion,high-pressure torsion,and cumulative rolling are very complicated and cannot be mass-produced.It is particularly difficult to study the microscopic evolution of large strain cold deformation.However,some conventional processing methods(rolling and drawing)also produce relatively large strains during the cold working process.These methods are very convenient and can easily simulate severe plastic deformation.In this subject,austenite-ferrite duplex stainless steel was selected,and through deformation treatment under different rolling amounts,the mechanical properties of the material from small strain to large strain and the microscopic evolution mechanism of the two phases were explored,and the following conclusions were drawn:(1)After 80% rolling,the duplex stainless steel has formed a typical layered ultrafine/nanocrystalline structure.The strength of the material reaches 1.3GPa,but the plasticity is seriously reduced,the uniform elongation is less than 2%,and there is almost no work hardening.In addition,the refining speed of the austenite phase is significantly faster than that of ferrite.(2)For austenite,the grain size has a great influence on twinning and stacking fault behavior.When the grain size is less than 20 nm,there will be dense stacking faults and twin nuclei with only four or five atomic layers in the grain,and a small amount of epsilon martensite will occasionally be produced.In addition,the accumulation of stacking faults can also induce small-angle grain boundaries.The dislocations stored on the small-angle grain boundaries can be used as the emission source of dislocations.A large number of dislocations are generated in other grains,thereby forming new stacking faults and twins.(3)For ferrite,the grain size has a certain effect on the type and evolution of dislocations:in coarse-grained crystals,the dislocations are mainly screw dislocations.When the size of the lamella decreases,the screw dislocation density begins to decrease,Replaced by a large number of edge and mixed dislocations.