Transformation-induced Plasticity Characteristics And Temperature Dependence Of Cr20Mn3Cu2NiN Lean Duplex Stainless Steel

Lean duplex stainless steel has good strength,plasticity and corrosion resistance due to its ferrite and austenite duplex structure,and is widely used in various industries.In this paper,Cr20Mn3Cu2Ni N lean duplex stainless steel was studied by cold rolling and hot rolling respectively.On this basis,experimental methods such as muffle heat treatment,tensile testing,hardness testing,optical microscopy(OM),electron backscatter diffraction(EBSD),transmission electron microscopy(TEM),X-ray diffraction(XRD)and nanoindentation were used to study the experimental steel.Firstly,the deformation mechanism of the test steel in the deformation process is explored.It is found that the test steel shows good strength and plasticity due to the interaction of many deformation mechanisms,such as phase transformation induced plasticity(TRIP),twinning induced plasticity(TWIP)and dislocation slip.The deformation of ferrite is mainly dislocation slip,and the transformation mechanism of martensite is mainlyγ→α′andγ→twins→α′。Secondly,the effects of solution temperature and deformation temperature on the microstructure and properties of the test steel were studied.It is found that the test steel is sensitive to temperature change,and only shows obvious TRIP effect at low temperature.With the increase of temperature,the stability of austenite gradually improves,which suppresses the TRIP effect.The deformation mechanism gradually changes from TRIP to TWIP,and then to dislocation slip,without obvious ductile brittle transition.Finally,the austenite stability of the test steel was preliminarily investigated.The results show that the"pop in"phenomenon in the process of nano indentation is caused by dislocation nucleation,martensite transformation and dislocation passing through low angle grain boundaries.Martensite nucleation load is defined as P_C,and the higher its value,the more stable austenite is.