The flow behavior of spray-formed FGH95 superalloy （similar to Rene 95） was investigated at tempera- tures ranging from 1050 to 1 140 ℃ and strain rate ranging from 0.01 to 10 s-1. At a given temperature and strain...The flow behavior of spray-formed FGH95 superalloy （similar to Rene 95） was investigated at tempera- tures ranging from 1050 to 1 140 ℃ and strain rate ranging from 0.01 to 10 s-1. At a given temperature and strain rate, flow stress increases quickly with increasing strain and then reaches a peak, then gradual decreases until high strain, and dynamic softening is observed. Utilizing the hyperbolic sine {unction and introducing the strain with non- linear fitting, the revised constitutive equations incorporating the effects of temperature, strain rate and strain for high temperature flow stress prediction of superalloy were established. The revised constitutive equations were im- planted into finite element software by second development to simulate the hot compression process successfully, and the effective stress and load stroke curves obtained by numerical simulation are good agreement with the experimen- tal results.展开更多
The corrosion behaviors of CNS-I and modified CNS-II were evaluated by exposing to superciritical water （SCW） at 550℃ and 25 MPa with a dissolved oxygen concentration of 200× 10 ^-9 for up to 1 000 h. Detailed...The corrosion behaviors of CNS-I and modified CNS-II were evaluated by exposing to superciritical water （SCW） at 550℃ and 25 MPa with a dissolved oxygen concentration of 200× 10 ^-9 for up to 1 000 h. Detailed corrosion results of these two alloys were provided, including the growth rate of the oxide scales, microstructure of the oxide scales, distribution of phases and alloying elements. The mass gains of CNS-I and modified CNS-II were 609.73 mg/dm2 and 459.42 mg/dm2 , respectively, after exposing to SCW for 1 000 h. A duplex oxide scale with an outer porous magnetite layer and an inner relatively dense magnetite/spinel-mixed layer was identified on CNS-I and modified CNS-II after the test. The oxide scales were rather porous at the beginning of the test but the porosity decreased with increase of the exposure duration. It was found that Fe was enriched in the outer oxide layer, Cr was enriched in the inner oxide layer and O existed at a very high concnetration in the whole oxide scale. Other alloying elements such as Mo, W, Mn were depleted from the outer oxide layer and showed slightly enrichment in the inner oxide layer. The distributution of Ni was different from other elements, it was enriched in the interface bewteen the base metal and the oxide scale and depleted in the outer and inner oxide layers.展开更多
Modified CNS-Ⅱ F/M steel was designed for in-core components of supercritical water cooled reactor. Study on the hot deformation behavior of modified CNS- Ⅱ F/M steel is of great importance for processing parameter ...Modified CNS-Ⅱ F/M steel was designed for in-core components of supercritical water cooled reactor. Study on the hot deformation behavior of modified CNS- Ⅱ F/M steel is of great importance for processing parameter planning and microstructure controlling during hot deformation. The hot deformation behavior of modified CNS-Ⅱ F/M steel was investigated through isothermal hot compression test at temperature ranging from 1 223 to 1 373 K and strain rate 0.01 to 10 s^-1. The true stress true strain data gained from compression tests were used to built constitu- tive equation of modified CNS-Ⅱ F/M steel. The influence of strain on the accuracy of constitutive analysis was in corporated, assuming strain has a influence on material constants. A 5th order polynominal equation with very good accuracy was used to represent the influence of strain on material constant. The flow stresses calculated from the constitutive equation were compared with test values in the whole experiment range and the absolute average error for the constitutive equation in predicting fl.ow stress is 4. 728 %. At last, the recrystallization behavior of modified CNS-Ⅱ F/M steel was investigated. The relationship of critical strain and peak strain with Zener-Hollomon parameter were given by an experimental equation.展开更多
The potential of spray forming for microstructural refining can be attractive to the production of superalloys.A200mm spray formed FGH95superalloy round billet that was produced using a single atomizer has considerabl...The potential of spray forming for microstructural refining can be attractive to the production of superalloys.A200mm spray formed FGH95superalloy round billet that was produced using a single atomizer has considerably homogeneous,small,equiaxed grains.The measured oxygen content is 2×10-5,and the measured porosity is only 0.6%.The achieved yield of deposit is in a good range of about 73.6%.The microstructure and tensile properties of nickel-based spray formed FGH95superalloy are analyzed.Also,effects of heat treatment on microstructure were discussed.The results show that the spray formed FGH95superalloy has higher isotropy in tensile property due to itsγ′phase homogeneous distribution and less defects in the microstructure.Regarding processing procedures,the different heat treatment processes affect the microstructure andγ′phase homogeneous distribution of spray formed FGH95superalloy.展开更多
基金Item Sponsored by National Natural Science Foundation of China(50974016)
文摘The flow behavior of spray-formed FGH95 superalloy （similar to Rene 95） was investigated at tempera- tures ranging from 1050 to 1 140 ℃ and strain rate ranging from 0.01 to 10 s-1. At a given temperature and strain rate, flow stress increases quickly with increasing strain and then reaches a peak, then gradual decreases until high strain, and dynamic softening is observed. Utilizing the hyperbolic sine {unction and introducing the strain with non- linear fitting, the revised constitutive equations incorporating the effects of temperature, strain rate and strain for high temperature flow stress prediction of superalloy were established. The revised constitutive equations were im- planted into finite element software by second development to simulate the hot compression process successfully, and the effective stress and load stroke curves obtained by numerical simulation are good agreement with the experimen- tal results.
基金Item Sponsored by National Basic Research Program of China(2007CB209800)
文摘The corrosion behaviors of CNS-I and modified CNS-II were evaluated by exposing to superciritical water （SCW） at 550℃ and 25 MPa with a dissolved oxygen concentration of 200× 10 ^-9 for up to 1 000 h. Detailed corrosion results of these two alloys were provided, including the growth rate of the oxide scales, microstructure of the oxide scales, distribution of phases and alloying elements. The mass gains of CNS-I and modified CNS-II were 609.73 mg/dm2 and 459.42 mg/dm2 , respectively, after exposing to SCW for 1 000 h. A duplex oxide scale with an outer porous magnetite layer and an inner relatively dense magnetite/spinel-mixed layer was identified on CNS-I and modified CNS-II after the test. The oxide scales were rather porous at the beginning of the test but the porosity decreased with increase of the exposure duration. It was found that Fe was enriched in the outer oxide layer, Cr was enriched in the inner oxide layer and O existed at a very high concnetration in the whole oxide scale. Other alloying elements such as Mo, W, Mn were depleted from the outer oxide layer and showed slightly enrichment in the inner oxide layer. The distributution of Ni was different from other elements, it was enriched in the interface bewteen the base metal and the oxide scale and depleted in the outer and inner oxide layers.
文摘Modified CNS-Ⅱ F/M steel was designed for in-core components of supercritical water cooled reactor. Study on the hot deformation behavior of modified CNS- Ⅱ F/M steel is of great importance for processing parameter planning and microstructure controlling during hot deformation. The hot deformation behavior of modified CNS-Ⅱ F/M steel was investigated through isothermal hot compression test at temperature ranging from 1 223 to 1 373 K and strain rate 0.01 to 10 s^-1. The true stress true strain data gained from compression tests were used to built constitu- tive equation of modified CNS-Ⅱ F/M steel. The influence of strain on the accuracy of constitutive analysis was in corporated, assuming strain has a influence on material constants. A 5th order polynominal equation with very good accuracy was used to represent the influence of strain on material constant. The flow stresses calculated from the constitutive equation were compared with test values in the whole experiment range and the absolute average error for the constitutive equation in predicting fl.ow stress is 4. 728 %. At last, the recrystallization behavior of modified CNS-Ⅱ F/M steel was investigated. The relationship of critical strain and peak strain with Zener-Hollomon parameter were given by an experimental equation.
基金Sponsored by National High Technology Research and Development Program(863Program)of China(2007AA03Z502)
文摘The potential of spray forming for microstructural refining can be attractive to the production of superalloys.A200mm spray formed FGH95superalloy round billet that was produced using a single atomizer has considerably homogeneous,small,equiaxed grains.The measured oxygen content is 2×10-5,and the measured porosity is only 0.6%.The achieved yield of deposit is in a good range of about 73.6%.The microstructure and tensile properties of nickel-based spray formed FGH95superalloy are analyzed.Also,effects of heat treatment on microstructure were discussed.The results show that the spray formed FGH95superalloy has higher isotropy in tensile property due to itsγ′phase homogeneous distribution and less defects in the microstructure.Regarding processing procedures,the different heat treatment processes affect the microstructure andγ′phase homogeneous distribution of spray formed FGH95superalloy.
