The preliminary chemical composition optimization and heat treatment parameters of Inconel 740H were investigated systematically. Six heats of experimental alloys （designated as heat 401 to heat 406） with varied che...The preliminary chemical composition optimization and heat treatment parameters of Inconel 740H were investigated systematically. Six heats of experimental alloys （designated as heat 401 to heat 406） with varied chemi- cal compositions were subjected to standard heat treatment at four different solution temperatures. Due to its superi- or combination of strength, ductility, and toughness together with its minor mechanical property changes at different solution temperatures, heat 405 was chosen as an optimized one to conduct further heat treatment investigations. The evolution of grain size with solution temperature for heat 405 was studied and the optimal solution temperature was determined. After solution treatment at the optimal temperature, four different cooling rates were applied to investi- gate the effect of cooling rate on the size distribution modal and mean radius of the γ′ precipitates. No bi-modal size distribution of γ′ precipitates was found for all cooling rates and water cooling was recommended for Inconel 740H. In addition, the effect of pre-aging at 800 ℃ for 16 h on the microstrueture of Inconel 740H aged for a long time was studied. It is found that pre-aging at 800 ℃ would result in bi-modal size distribution of γ′ precipitates after long time aging at 750 ℃ compared with mono modal size distribution in samples without pre-aging, which might be caused by the difference in initial size distribution modal before Ostwald ripening of γ′ precipitates in samples with and without pre-aging at 800 ℃.展开更多
Measurements of stored energy have been obtained for samples of copper cold-rolled to von Mises strains between 0.42 and 5.21 using both differential scanning calorimetry （DSC）, and based on measurements of microstr...Measurements of stored energy have been obtained for samples of copper cold-rolled to von Mises strains between 0.42 and 5.21 using both differential scanning calorimetry （DSC）, and based on measurements of microstructural parameters in the transmission electron microscope （TEM）. In both cases, a linear increase in stored energy with strain is found. The ratio between the two measured values varies, however, over a significant range, indicating that some caution is needed in determining the relative difference in energy associated with deformation microstructure heterogeneities in a given sample. Comparison of the stored energy with the flow stress suggests that the TEM-based measurements reflect the dislocation density content responsible for the flow stress, but that the DSC technique additionally measures other contributions to the stored energy, such as the presence of balanced internal stresses.展开更多
基金Sponsored by High-Tech Research and Development Project of China(2102AA03A501)
文摘The preliminary chemical composition optimization and heat treatment parameters of Inconel 740H were investigated systematically. Six heats of experimental alloys （designated as heat 401 to heat 406） with varied chemi- cal compositions were subjected to standard heat treatment at four different solution temperatures. Due to its superi- or combination of strength, ductility, and toughness together with its minor mechanical property changes at different solution temperatures, heat 405 was chosen as an optimized one to conduct further heat treatment investigations. The evolution of grain size with solution temperature for heat 405 was studied and the optimal solution temperature was determined. After solution treatment at the optimal temperature, four different cooling rates were applied to investi- gate the effect of cooling rate on the size distribution modal and mean radius of the γ′ precipitates. No bi-modal size distribution of γ′ precipitates was found for all cooling rates and water cooling was recommended for Inconel 740H. In addition, the effect of pre-aging at 800 ℃ for 16 h on the microstrueture of Inconel 740H aged for a long time was studied. It is found that pre-aging at 800 ℃ would result in bi-modal size distribution of γ′ precipitates after long time aging at 750 ℃ compared with mono modal size distribution in samples without pre-aging, which might be caused by the difference in initial size distribution modal before Ostwald ripening of γ′ precipitates in samples with and without pre-aging at 800 ℃.
基金support from the Danish National Research Foundation(No.DNRF86-5)the National Natural Science Foundation of China(Nos.51261130091 and 51171085)to the Danish-Chinese Center for Nanometals
文摘Measurements of stored energy have been obtained for samples of copper cold-rolled to von Mises strains between 0.42 and 5.21 using both differential scanning calorimetry （DSC）, and based on measurements of microstructural parameters in the transmission electron microscope （TEM）. In both cases, a linear increase in stored energy with strain is found. The ratio between the two measured values varies, however, over a significant range, indicating that some caution is needed in determining the relative difference in energy associated with deformation microstructure heterogeneities in a given sample. Comparison of the stored energy with the flow stress suggests that the TEM-based measurements reflect the dislocation density content responsible for the flow stress, but that the DSC technique additionally measures other contributions to the stored energy, such as the presence of balanced internal stresses.
