| Duplex stainless steels exhibit comprehensive properties of both austenite and ferrite due to their uniqueα/γduplex microstructure.However,it faces a series of problems in the processing and use,such as harmful precipitated phase in the service of medium and low temperature environment（below 1000℃）,in the cold rolling forming process,due to deformation induced phase transformation,resulting in poor plasticity of dual-phase stainless steel,which obviously limits the wide application of dual-phase stainless steel.In this paper,the hot-rolled 2205 duplex stainless steel was taken as the research object,and the microstructure evolution of duplex stainless steel during solution treatment and aging treatment was studied by OM,SEM/EDS,XRD and other characterization methods.Effects of changes in mechanical properties.In addition,EBSD was used to characterize the change of grain size and texture evolution in the microstructure after cold rolling and annealing,to explore the effect of cold rolling/annealing process on the microstructure and mechanical properties of materials,and to develop the 2205 toughening technology.The main contents and results are as follows:（1）Based on the solution+aging heat treatment method,theα/γtwo-phase ratio and the precipitation law ofσphase were investigated.The influence of solution treatment temperature on the ratio and mechanical properties was systematically studied.1050℃was selected as the pretreatment temperature for aging treatment.The precipitation mechanism ofσphase was clarified through the aging treatment experiment,that is,the eutectoid decomposition ofαphase to obtainγ2 andσphase.The most sensitive precipitation temperature ofσphase is850℃,and the longer the aging time is,the moreσphase is precipitated.The effect ofσon the mechanical properties of the material was explored through tensile experiments and tensile fracture morphology observation.The precipitation behavior ofσphase will seriously damage the plasticity of the material.（2）The effect of cold rolling deformation on the microstructure and mechanical properties of 2205 duplex stainless steel,the cold rolling deformation experiment of 2205 duplex stainless steel was carried out,and the deformation induced martensitic transformation behavior during the cold rolling deformation was clarified by combining the microstructure characterization.Then,the cold rolled 2205 duplex stainless steel was annealed at high temperature（1000～1150℃）.The grain size of the material was obviously refined based on the static recrystallization behavior,and the mechanical properties were improved to some extent.After annealed at 1050℃,the yield strength increased to 586.5MPa,and the tensile strength increased to 835.3MPa.（3）Explore the grain refinement degree and annealing texture evolution law in the microstructure after cold rolling/annealing,and analyze the relationship between texture evolution,microstructure and mechanical properties.The results show that:The austenitic brass texture and ferriteγorientation texture produced in the annealing process are beneficial to the improvement of the strength of duplex stainless steel,and the combination process of cold rolling and annealing（1050℃）can obtain strong plasticity and excellent duplex stainless steel,but the high annealing temperature often leads to grain coarsing,which reduces the mechanical properties of the material to some extent.（4）Through the aging treatment of the cold-rolled/annealed material,the influence of cold-rolled/annealed process on the precipitation ofσphase is studied.The results show that cold-rolled deformation will promote the precipitation ofσphase and further deteriorate the duplex stainless steel.plasticity. |
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