Study On Mechanical And Energy Characteristics And Deformation Damage Failure Mechanism Of Lean Duplex Stainless Steel Sheet

Lean duplex stainless steel materials have the characteristics of biphasic distribution of ferrite and austenite.On the basis of this structure,the introduction of TRIP（Transformation Induced Plasticity）effects make it have high strength,good plastic forming ability and corrosion resistance,so it can be widely used in various industrial fields,especially in the automobile industry.At the same time,the stamping and forming process of metal plate occupies a large proportion in the automobile industry.Therefore,it has broad application prospect to study the plastic deformation behavior and formability of lean duplex stainless steel sheet.In this study,a new kind of lean duplex stainless steel material with TRIP effect was taken as the research object,and its forging billets were hot-rolled and a certain batch of sheets with uniform thickness distribution and good quality were obtained.Through the corresponding mechanical properties test and microstructure characterization,the differences of mechanical properties of test steel sheet under different influencing factors were analyzed.After solution treatment at 1000°C and control of the strain rate of 10^-3/s,it is determined that the hot rolled sheet has excellent comprehensive mechanical properties at room temperature.At the same time,it is found that the test steel sheet shows obvious anisotropy difference,and a hardening model based on the Hill-48 anisotropy yield criterion is established.By means of the metallographic observation,SEM and TEM,two mechanisms of the martensitic transformation of the two-phase steel plate have been investigated:γ→ε→α’andγ→α’.The ferrite deformation is mainly based on dislocation slip.Meanwhile,the dynamic model of martensitic transformation is established.Based on the digital measurement system,fracture tests were carried out on samples of different structural sizes taken from hot-rolled plates.The fracture of each sample showed ductile fracture.It was found that the fracture of plates was significantly correlated with the structural size of the samples and the corresponding stress state.The orientation of dimple holes in arc-shaped notched specimens and triangular notched specimens is basically perpendicular to the loading direction,while the dimple holes in shear samples form sliding channels along the loading direction.Meanwhile,based on the DIC test results and the finite element simulation method,the Lou-2013 ductile fracture criterion applicable to duplex stainless steel hot-rolled plates is established.In order to continue to explore the forming ability of hot rolled sheet test.