Research On Deformation Inducedplastic Behavior Of The Lean Duplexstainless Steel

Replacing the traditional austenitic stainless steel,duplex stainless steel can be applied to the manufacture of ordinary passenger car parts.It can meet the need of a new generation of vehicles for high performance and low cost and environmentally friendly requirements.However,due to the unique two-phase structure and the different work hardening behavior of the two phase,the deformation compatibility of duplex stainless steel is poor,which leads to poor plasticity.Now it has become a major bottleneck in the automotive application.In view of the lean duplex stainless steel alloy system,with Mn-N instead of Ni,the stability of austenite in steel is reduced,showing metastable state.In the process of deformation,TRIP or?and?TWIP effect can be used to increase the plasticity,which can break the bottleneck.Therefore,it is of great significance to find out the deformation induced plasticity effect and mechanism of the duplex stainless steel.In this paper,a kind of duplex stainless steel with metastable austenite phase is studied,The effects of solid solution heat treatment,deformation parameters?strain rate,temperature?and other key factors on the deformation induced plasticity effect were investigated systematically.The main results are as follows:?1?The deformation mechanism of austenite dominates the deformation of test steel.When the metastable austenite is stretched,the deformation mechanism of the austenite is diversified,which can include transformation induced martensite?TRIP effect?,twinning induced plasticity?TWIP effect?,dislocation slip,etc..The deformation mechanism of ferrite in the test steel is dislocation slip.Through the advanced technology such as TEM and EBSD,it is found that the mechanism of martensitic transformation is????and??????.In addition,the??-martensite can be nucleated at the cross point of the?-martensite band.?2?With the increase of solution temperature,the stacking fault energy can be changed.When the deformation mechanism of the test steel is below 1050?,the TRIP effect is the main factor,and the TWIP effect is the main factor at the temperature of at1100?¹150?.The TWIP effect will be replaced by dislocation slip at the temperature of 1200?.The duplex stainless steel has the TRIP effect and the TWIP effect,and has the characteristics of multi stage work hardening,and shows a higher stage hardening behavior under the combined effect of TRIP effect and TWIP effect.?3?The rate sensitive point of the test steel is 0.1s^-1and the deformation temperature sensitive point of the test steel is 70?.When the strain rate is lower than 0.1s^-1and the deformation temperature is lower than 70?,the deformation induced plasticity effect of the test steel is higher.When the strain rate is higher than 0.1s^-1and the deformation temperature is higher than 70?,the plasticity and strength of the test steel decrease sharply,and the deformation mechanism is dominated by dislocation slip.