Study On Hot Deformation Behavior Of Lean Duplex Stainless Steel Under Different Phase Distribution Directions

Duplex stainless steel which has the excellent performance both ferrite stainless steel and austenitic stainless steel.While lean duplex stainless steel is a kind of duplex stainless steel using N,Mn in place of Ni,Mo,which in the premise of ensuring material properties significantly reduced Production costs,is the focus of the future development of alloy materials.However,due to the mechanical properties and microstructure of the composition phase is different,resulting in the two phases prone to deformation is not coordinated,causing stress,strain concentration,induced material to form internal defects.Therefore,it is important to understand the thermal deformation behavior of lean duplex stainless steel,and to quantitatively describe the stress and strain distribution rules of the two phases during deformation.It is very important to improve the hot forming performance of the material and the development of the new steel.In this paper,a kind of lean duplex stainless steel was used as the object of study.The hot deformation behavior was analyzed by the combination of hot compression experiment,hot processing map and metallographic observation.Based on the theoretical derivation,the relationship between the deformation compatibility of duplex stainless steel with deformation conditions and the two-phase distribution was determined.Through the hot compression experiment,the rheological curve of the experimental steel was obtained,and the constitutive equation of the experimental steel based on the characteristic stress and the whole stress constitutive equation considering the strain compensation were established.The energy dissipation efficiency factors and material instability parameters under different deformation conditions,different strain were calculated.Based on this,the hot processing map of the experimental steel was drawn and the optimum hot process range was obtained.Analyzed the typical microstructure after hot deformation with deformation temperature of 1000～1200℃ and strain rate of 0.01～10s-1,and mastered microstructure evolution of the experimental steel in the process of deformation.In addition,the study found that,when deformed at the temperature of 1200°C,the grain boundary(phase boundary)of the experimental steel into jagged,and this feature become more obviously under the lower the strain rate.Based on the hybrid rule,the stress distribution model,the strain distribution model and the finite element model were established.The distribution of stress and strain in the two phases were studied when loaded in the lateral direction and in the longitudinal direction.It was found that the two phases were coordinated and deformed in the longitudinal direction,and the phase boundary is not easy to produce defects.When loaded in the transverse direction,the strain distribution of the two phases were not uniform and the deformation compatibility was poor.Two-phase stress together to obtain the total stress of duplex stainless steel.