Microstructure Evolution And Mechanical Properties Of 316 Stainless Steel:Strain Rate Effect

AISI 316 stainless steel having an austenitic crystalline structure,is a face-centered cubic material.Owing to its superior properties,such as high strength at elevated temperature,high resistance to corrosion ect,AISI 316 austenitic stainless steel is considered as one of the most widely used stainless steel in the maritime and offshore sectors.At present,the tensile properties of 316 austenitic stainless steel have been further studied,but most of them are aimed at the mechanical properties and fracture surface under specific loading rate,and little attention has been paid to microstructure evolution,especially the influence of strain rate on microstructure evolution and mechanical properties during tensile process.In the present study,the different strain rate from 10^-4s^-11 to 10^-3s^-1,on the microstructure evolution and strain hardening behavior at the AISI 316 austenitic stainless steel subjected to interrupted uniaxial tensile tests are investigated.The detailed investigation on the microstructure and texture evolution of the undeformed and deformed specimens at the various strain level at 5%,20%,40%are carried out by the scanning electron microscope,three dimensional topography measurement system,atomic force microscope and electron backscatter diffraction.And the strain hardening behavior and the tensile properties are also examined by monotonic tensile tests.The main findings of the present work are as follows:?1?At a constant strain rate,the increase of the level of deformation causes the increment of the roughness of the surface,the extrusion height,the plastic strain value,the fraction of low angle grain boundaries and of geometrically necessary dislocations.A three-stage work hardening behavior is identified with??decreases significantly in stage I,then increases gradually in stage II and finally decreases slightly in stage III.?2?For a given strain level,the increase of the strain rate results in not only the decrease of the roughness of a surface but also the increase of the extrusion height,the fraction of low angle grain boundaries and of geometrically necessary dislocations;strain hardening of 316 austenitic stainless steel decreased with strain rate increasing.?3?The increase of the strain rate gives rise to the yield strength and the elongation at break but gradually decreases the ultimate tensile strength;through fracture morphology observation,it is revealed that the number of dimple is increased and thus,the size of dimple is decreased.Through the present research work,the microstructure evolution and mechanical response of AISI 316 stainless steel during tensile deformation process has been elucidated,and the strain rate dependent active deformation mechanism of the target material is further revealed.These elements obtained for AISI 316 stainless steel can further lay a theoretical foundation for engineering applications.