2022 年 62 巻 5 号 p. 963-969
Microscale changes in the microstructure of and stress distribution in a polycrystalline duplex stainless steel comprising ferrite and austenite caused by plastic tensile deformation are characterized to understand the microscopic processes of the crystal plasticity of dual-phase steel. Because the ferrite of the body-centered-cubic structure and the austenite of the face-centered-cubic structure exhibit different mechanical properties, texture changes in the ferrite and austenite caused by uniaxial tensile deformation are investigated based on the electron backscatter diffraction pattern. Residual stresses formed by tensile deformation are characterized using a two-dimensional method based on X-ray diffraction. The results show that the steel exhibits a banded microstructure of ferritic coarse grains and austenitic fine grains, and that the texture is changed by tensile deformation. The grains in the steel are rotated by tensile deformation depending on their orientation with respect to the tensile axis. Residual stress measurements demonstrate that compressive stresses remain in the elastically hard ferrite after tensile deformation, whereas tensile stresses remain in the austenitic phase. The formation of the residual stresses are discussed based on the characteristic microscale plasticity of ferrite and austenite.
