In order to clarify the reason why the creep rupture time of pre-strained Ni-23Cr-7W Alloy (HR6W) is longer than that of the non-pre-strained HR6W, microstructures of HR6W after a series of creep tests were investigat...In order to clarify the reason why the creep rupture time of pre-strained Ni-23Cr-7W Alloy (HR6W) is longer than that of the non-pre-strained HR6W, microstructures of HR6W after a series of creep tests were investigated. The creep tests were conducted at 750°C, 90 and 100 MPa. In the pre-strained samples, the grain boundary shielding ratio by precipitates was larger than that of the non-pre-strained sample. In addition, in the pre-strained samples the size of the M23C6 carbide in the grains was finer than in the non-pre-strained sample. The W content in the M23C6 carbide in the pre-strained samples tended to be larger than in the non-pre-strained sample. Therefore, the Ostwald ripening of the carbide was delayed and the size of M23C6 carbide was thought to be fine for a long time. These observations show that creep strength in the pre-strained samples is higher than that of the non-pre-strained sample because of both precipitation strengthening inside of the grains and grain boundaries.展开更多
This paper studies a method for obtaining the stress with plastic deformation by finding the plastic strain on U-bent specimens of austenitic stainless steel that have been subjected to large plastic deformation using...This paper studies a method for obtaining the stress with plastic deformation by finding the plastic strain on U-bent specimens of austenitic stainless steel that have been subjected to large plastic deformation using the EBSD (Electron Backscatter Diffraction) method. The Mises stress calculated on the basis of the KAM of the EBSD shows good agreement with the stress that can be geometrically calculated from the U-bent specimens. In contrast, general methods for measuring residual stress on the basis of elastic strain produce residual stress measurement results that differ specimen by specimen. Thus, for true strain not less than 0.05, stress estimation based on the EBSD method produces better results than other general methods.展开更多
文摘In order to clarify the reason why the creep rupture time of pre-strained Ni-23Cr-7W Alloy (HR6W) is longer than that of the non-pre-strained HR6W, microstructures of HR6W after a series of creep tests were investigated. The creep tests were conducted at 750°C, 90 and 100 MPa. In the pre-strained samples, the grain boundary shielding ratio by precipitates was larger than that of the non-pre-strained sample. In addition, in the pre-strained samples the size of the M23C6 carbide in the grains was finer than in the non-pre-strained sample. The W content in the M23C6 carbide in the pre-strained samples tended to be larger than in the non-pre-strained sample. Therefore, the Ostwald ripening of the carbide was delayed and the size of M23C6 carbide was thought to be fine for a long time. These observations show that creep strength in the pre-strained samples is higher than that of the non-pre-strained sample because of both precipitation strengthening inside of the grains and grain boundaries.
文摘This paper studies a method for obtaining the stress with plastic deformation by finding the plastic strain on U-bent specimens of austenitic stainless steel that have been subjected to large plastic deformation using the EBSD (Electron Backscatter Diffraction) method. The Mises stress calculated on the basis of the KAM of the EBSD shows good agreement with the stress that can be geometrically calculated from the U-bent specimens. In contrast, general methods for measuring residual stress on the basis of elastic strain produce residual stress measurement results that differ specimen by specimen. Thus, for true strain not less than 0.05, stress estimation based on the EBSD method produces better results than other general methods.
