Mechanical And Corrosive Properties Of Bulk Nanocrystalline 304 Stainless Steel

304 stainless steel,with good corrosion resistance and machinability,is widely used in electric power,metallurgy and chemical industry.The environment of steel has become increasingly complex in recent years,and people’s demand for steel service life is increasing.Nanocrystallization of metallic materials has gradually become an effective way to improve the resistance of materials.Therefore,it is significant for nanotechnology and industrial production to research the tensile behavior and fractures of nanocrystalline.Bulk nanocrystalline 304 stainless steel(BN-SS304)in this topic was prepared by severe rolling technique with its conventional polycrystalline counterpart(CP-SS304).Phases and surface states of two contrast samples are analyzed on the basis of tensile deformation.Simultaneously,it is studied for corrosive behavior of tensile samples and undeformed materials in hydrochloric acid solution.The tensile tests with a constant rate of BN-SS304 and CP-SS304 are carried out,and Micro Vickers-hardness are measured near the fracture.Phases and surface states of BN-SS304 tensile sample are studied by X-ray diffraction,scanning electron microscopy,confocal laser scanning microscopy and so on.The results show that yield and tensile strength of BN-SS304 are higher than those of CP-SS304,the elongation of BN-SS304 is 34.5%,and the elastic region before yielding of BN-SS304 is larger than that of CP-SS304.Although the volumes of BN-SS304 a’-martensite transformation are less during plastic deformation,it has a stronger ability to resist the damage behavior and the surface roughness caused by tensile test is relatively smaller.Another focus of this research is corrosion and wetting experiment of BN-SS304 in hydrochloric acid solution,and material surfaces are analyzed by ultraviolet and X-ray photoelectron spectroscopy.The results show that BN-SS304 has good corrosion resistance,it is due to the higher binding energies of Fe2+,Fe3+,Fe0 and Cl-in corrosion products and corrosion behavior is difficult to continue.Moreover,the fracture of BN-SS304 also has excellent corrosion resistance without crevice corrosion.Not only because of the higher ionic binding energies in corrosion products,the work function in BN-SS04 fracture is larger and wetting property of water on the fracture is poor.Meanwhile,near the fracture,the content of high binding energy ion Fe3+ in corrosion products is obviously increased.And it is caused the increased number of high energy valence electrons,thereby to improve the stability of corrosion products in BN-SS304 fracture.