The microstructures of B2-ordered NiA1 containing α-Fe precipitates have been investigated in terms of transmission electron microscopy. Fine precipitation of α-Fe (bcc structure) occurs in NiA1 by aging around 973...The microstructures of B2-ordered NiA1 containing α-Fe precipitates have been investigated in terms of transmission electron microscopy. Fine precipitation of α-Fe (bcc structure) occurs in NiA1 by aging around 973K. The aging behavior was investigated by microhandness measurements and the temperature dependence of the yield strength of precipitate- comaining B2- ordered NiA1 was investigated by compression tests over the temperature range of 673-1273K. The fine precipitation of α-Fe was found to enhance greatly the low and intermediate temperature yield strength. When the deformation temperature is over 1073K, the strength of precipitate- containing NiA1 was comparable to ternary solid solution hardening NiA1-Fe. Dislocations bypass the particles during deformation and typical Orowan loops were observed surrounding the or-Fe particles after deformation.展开更多
The cyclic deformation behavior and microstructure evolution of the 55Ni−23Cr−13Co nickel-based superalloy were studied at 750℃ under the strain amplitudes from 0.35%to 0.6%.Coffin−Manson−Basquin and Smith−Watson−Top...The cyclic deformation behavior and microstructure evolution of the 55Ni−23Cr−13Co nickel-based superalloy were studied at 750℃ under the strain amplitudes from 0.35%to 0.6%.Coffin−Manson−Basquin and Smith−Watson−Topper relationships were employed,which satisfactorily predicted the fatigue life of the alloy under various strain amplitudes.The superalloy showed an initial cyclic hardening as a result of the interaction between the dislocations and the precipitates,and following cyclic softening behavior mainly due to the shearing of theγ′phase by dislocations and dislocations recovery under all strain amplitudes.Microstructure analyses showed that the M_(23)C_(6) carbides exhibited a continuous-chain distribution at lower strain amplitudes,while they showed a discontinuous distribution at higher strain amplitudes.As the strain amplitude increased,the size of theγ′phase decreased as the consequence of repeated shearing by dislocations.Fracture mechanisms were analyzed.Under higher strain amplitudes,cavities preferred to form around grain boundaries.展开更多
The Au ion-irradiation experiments of GH3535 alloy,a candidate alloy structural material for molten salt reactor,was carried out in this study.Herein,isochronous annealing experiments were conducted from 200 to 850 ℃...The Au ion-irradiation experiments of GH3535 alloy,a candidate alloy structural material for molten salt reactor,was carried out in this study.Herein,isochronous annealing experiments were conducted from 200 to 850 ℃ to clarify the evolution behavior of damage defects with increasing temperature.The coarsening of dislocation loops and formation and dissolution of precipitates with increasing annealing temperature were characterized by transmission electron microscopy.Nanoindentation was performed to measure the variation of hardness caused by irradiation.Additionally,the relationship between irradiation hardening and microstructure evolution was established.This study lays a foundation for the evaluation of irradiation damage properties of GH3535 alloy at different annealing temperatures.展开更多
Mechanical properties and microstructure changes have been investigated on anew nickel-base superalloy after long-term aging at 700 deg C. It is found that the majorprecipitates of the tested alloy are MC, M_(23)C_6, ...Mechanical properties and microstructure changes have been investigated on anew nickel-base superalloy after long-term aging at 700 deg C. It is found that the majorprecipitates of the tested alloy are MC, M_(23)C_6, M_6C and y' in the course of long4erm aging at700 deg C. The carbides maintain good thermal stability with the aging time up to 5008 h. The growthrate of gamma prime precipitates is relatively high in the early aging period and then slows down.The coarsening behavior of gamma prime follows a diffusion-controlled growth procedure. The roomtemperature Rockwell hardness of the alloy aged at 700 deg C increases slightly at the initial stageof aging, but it decreases with the prolonged time. It mainly depends on the size of gamma prime.In comparison with Nimonic alloy 263, the new alloy characterizes with higher tensile andstress-rupture strengths at high temperatures. The new nickel-base superalloy offers a combinationof microstructure stability, strength, ductility and toughness at 700 deg C.展开更多
文摘The microstructures of B2-ordered NiA1 containing α-Fe precipitates have been investigated in terms of transmission electron microscopy. Fine precipitation of α-Fe (bcc structure) occurs in NiA1 by aging around 973K. The aging behavior was investigated by microhandness measurements and the temperature dependence of the yield strength of precipitate- comaining B2- ordered NiA1 was investigated by compression tests over the temperature range of 673-1273K. The fine precipitation of α-Fe was found to enhance greatly the low and intermediate temperature yield strength. When the deformation temperature is over 1073K, the strength of precipitate- containing NiA1 was comparable to ternary solid solution hardening NiA1-Fe. Dislocations bypass the particles during deformation and typical Orowan loops were observed surrounding the or-Fe particles after deformation.
基金financial supports from the National Natural Science Foundation of China (Nos. 52025052, 51975405)。
文摘The cyclic deformation behavior and microstructure evolution of the 55Ni−23Cr−13Co nickel-based superalloy were studied at 750℃ under the strain amplitudes from 0.35%to 0.6%.Coffin−Manson−Basquin and Smith−Watson−Topper relationships were employed,which satisfactorily predicted the fatigue life of the alloy under various strain amplitudes.The superalloy showed an initial cyclic hardening as a result of the interaction between the dislocations and the precipitates,and following cyclic softening behavior mainly due to the shearing of theγ′phase by dislocations and dislocations recovery under all strain amplitudes.Microstructure analyses showed that the M_(23)C_(6) carbides exhibited a continuous-chain distribution at lower strain amplitudes,while they showed a discontinuous distribution at higher strain amplitudes.As the strain amplitude increased,the size of theγ′phase decreased as the consequence of repeated shearing by dislocations.Fracture mechanisms were analyzed.Under higher strain amplitudes,cavities preferred to form around grain boundaries.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.12022515 and 11975304)the Youth Innovation Promotion Association,Chinese Academy of Sciences(Grant No.Y202063)。
文摘The Au ion-irradiation experiments of GH3535 alloy,a candidate alloy structural material for molten salt reactor,was carried out in this study.Herein,isochronous annealing experiments were conducted from 200 to 850 ℃ to clarify the evolution behavior of damage defects with increasing temperature.The coarsening of dislocation loops and formation and dissolution of precipitates with increasing annealing temperature were characterized by transmission electron microscopy.Nanoindentation was performed to measure the variation of hardness caused by irradiation.Additionally,the relationship between irradiation hardening and microstructure evolution was established.This study lays a foundation for the evaluation of irradiation damage properties of GH3535 alloy at different annealing temperatures.
文摘Mechanical properties and microstructure changes have been investigated on anew nickel-base superalloy after long-term aging at 700 deg C. It is found that the majorprecipitates of the tested alloy are MC, M_(23)C_6, M_6C and y' in the course of long4erm aging at700 deg C. The carbides maintain good thermal stability with the aging time up to 5008 h. The growthrate of gamma prime precipitates is relatively high in the early aging period and then slows down.The coarsening behavior of gamma prime follows a diffusion-controlled growth procedure. The roomtemperature Rockwell hardness of the alloy aged at 700 deg C increases slightly at the initial stageof aging, but it decreases with the prolonged time. It mainly depends on the size of gamma prime.In comparison with Nimonic alloy 263, the new alloy characterizes with higher tensile andstress-rupture strengths at high temperatures. The new nickel-base superalloy offers a combinationof microstructure stability, strength, ductility and toughness at 700 deg C.
