To investigate the influence of W and Al on the microstructure and mechanical properties of a high-W superalloy,the Thermo-Calc calculation was utilized to simulate the microstructure with various W and Al contents.Th...To investigate the influence of W and Al on the microstructure and mechanical properties of a high-W superalloy,the Thermo-Calc calculation was utilized to simulate the microstructure with various W and Al contents.The results indicated that the concentration of W and Al exceeded 15.7 wt%and 5.9 wt%,respectively,the abnormal tungsten-richα-W phase would precipitate.Compared with the results of orthogonal experiment,the precipitation ofα-W phase is consistent with thermodynamic calculation results.The presence of Al not only influenced the precipitation ofα-W phase but also impacted the eutectic content and theγʹ-size,both of which showed an increase with higher Al concentrations.Excessive W and Al contents promoted the precipitation ofα-W phase,escalating the site of crack nucleation,and ultimately decreasing the plasticity.In the process of creep deformation(975℃/235 MPa),the raftedγ'phases were more continuous with increasing W contents,which increased the difficulty of dislocation climbing.As Al content increased,the density of interfacial dislocation network increased.The dislocations were entangled with each other,and the hindrance of dislocation movement was enhanced,which improved the stress rupture life.However,the precipitation of the hard and brittleα-W phase was attributed to the excessive W and Al,which increased the tendency of crack formation and significantly diminished the stress rupture life.The alloy exhibited the highest stress rupture life of 110.46 h when the W and Al contents were 15.7 wt%and 5.9 wt%,respectively.展开更多
The effect of carbon content on the microstructures and stress rupture properties of a newly developed polycrystalline Ni-based superalloy with high Cr content has been studied.It was observed that both grain size and...The effect of carbon content on the microstructures and stress rupture properties of a newly developed polycrystalline Ni-based superalloy with high Cr content has been studied.It was observed that both grain size and the number of carbides increased with an increase in carbon content.After heat treatment,granular M_(23)C_(6)carbides were dispersed around MC carbides along grain boundaries and inside grains.The quantity of granular M_(23)C_(6)carbides increased while their sizes decreased.These findings can be verified with the results of thermodynamic calculation and differential scanning calorimetry analysis.The stress rupture times(975℃/225 MPa)increased from 13.3 to 25.5 h with the carbon content increased from 0.1 to 0.2 wt.%.The improvement can be attributed to two primary factors.Firstly,grain boundary is typically weak region during deformation process and the grain size increased as carbon content increased in the alloy.Secondly,carbides act as hindrances to impede dislocation movement,leading to dislocation entanglement.As carbon content rose,the quantity of carbides in interdendritic regions and grain boundaries increased,providing a certain degree of strengthening effect and resulting in a longer stress rupture time.展开更多
The Portevin-Le Chatelier(PLC) effects in a wrought Ni-base superalloy with different γ' precipitates contents have been investigated. Detailed analysis on the serration type of the tensile curves indicates that ...The Portevin-Le Chatelier(PLC) effects in a wrought Ni-base superalloy with different γ' precipitates contents have been investigated. Detailed analysis on the serration type of the tensile curves indicates that the γ' precipitates have a decisive influence on the transformation from normal to inverse PLC behavior, which is rarely proposed in other works. It is considered that the γ' precipitates play the same role in PLC effect as temperature and strain rate for the investigated wrought Ni-base superalloy.展开更多
The application and component designs of single crystal superalloys are restricted by the precipitation of topologically closed packed(TCP)phases,which can deteriorate the microstructural stability of the alloys sever...The application and component designs of single crystal superalloys are restricted by the precipitation of topologically closed packed(TCP)phases,which can deteriorate the microstructural stability of the alloys severely.Limited researches concerning the type and morphology evolution of TCP phases under elevated temperature conditions have been reported previously.In the present work,three Re-containing single crystal alloys were designed to investigate TCP phase evolution via long term isothermal exposure tests at 1120℃while the effects of Re on the microstructural characteristic and elements segregation were also clarified.The results showed that the addition of Re increased the instability of the alloys and the volume fraction of the TCP phases exceeded 5 vol%when the Re content reached 3 wt%.The increasing Re content had also raised the precipitation temperature of TCP phases but it did not change the type of them after long term aging;all the TCP particles were identified asμphase in this study.Moreover,the elements segregation became considerably serious as Re addition increased constantly,which brought about various morphologies of theμphase in the experimental alloys.In particular,the rod-like and needle-likeμphases demonstrated the typical orientation withinγmatrix while the blockyμphase was dispersedly distributed in the space.No specific orientation relationship could be observed in theμphase when the addition of Re exceeded certain threshold value.展开更多
The formation and evolution of M_(6)C carbides in high-W superalloy following solution treatment was investigated at different temperatures.Initially,during solid solution treatment,MC and M_(6)C carbides was precipit...The formation and evolution of M_(6)C carbides in high-W superalloy following solution treatment was investigated at different temperatures.Initially,during solid solution treatment,MC and M_(6)C carbides was precipitated in the alloy.As the temperature increased,the morphology of M_(6)C carbides transitioned from granular to needle-like.During the solution treatment at 1255℃,the MC carbides degraded and transformed into M_(6)C carbides,forming a symbiotic relationship between them.Nonetheless,no clear orientation relationship was observed between the two types of carbides.After further increasing the temperature to 1270℃,the precipitation of needle-like M_(6)C carbides in the dendrite arm was confirmed.This was supported by electron probe X-ray micro-analyzer and selected area electron diffraction patterns.Subsequently,a detailed examination of the three-dimensional morphology and orientation relationship of the needle-like phase with the matrix was carried out using focused-ion-beam and transmission electron microscopy techniques.The results indicated that the flat interface of the needle phase exhibited a specific orientation relationship with the matrix.However,in the three-dimensional plane,the interfaces between the needle-like phase and the matrix were not straight.Furthermore,no clear orientation relationship between the non-straight interfaces and the matrix was observed.As the solution temperature increased,the tensile properties at room temperature progressively decreased,while the stress rupture properties peaked at 1260℃,suggesting that the alloy demonstrated its optimal comprehensive performance at this temperature.A subsequent analysis was conducted on the longitudinal section of the fracture using electron backscattered diffraction.The results showed a noticeable concentration of stress at the interface between MC and M_(6)C carbides,which ultimately led to crack initiation at this interface.In addition,as the solid solution temperature increased,the quantity of symbiotic phases also increased.This phenomenon led to the initiation of cracks at multiple locations,which then propagated and interconnected.As a consequence,the tensile properties and stress rupture life of the alloy progressively deteriorated.展开更多
Increasing the print quality is the critical requirement for the additive manufactured complex part of aero-engines of nickel-based superalloys.A study of the effects of Co and Nb on the crack is performed focusing on...Increasing the print quality is the critical requirement for the additive manufactured complex part of aero-engines of nickel-based superalloys.A study of the effects of Co and Nb on the crack is performed focusing on the selective laser melting(SLM)nickel-based superalloy.In this paper,the solvus temperature of γ',crack characteristics,microstructure,thermal expansion,and mechanical properties of SLM nickel-based superalloy are investigated by varying the content of Co and Nb.The alloy with 15Co/0Nb shows the highest comprehensive quality.Nb increases the crack risk and thermal deformation,and then Co accelerates the stress release.Therefore,Co is an extremely important alloying element for improving the quality of SLM nickel-based superalloy.Finally,the crack growth kinetics and the strain difference are discussed to reveal the SLM crack regular that is affected by time or temperature.The analysis work on the effect of alloying elements can obtain an effective foundational theory to guide the composition optimization of SLM nickel-based superalloys.展开更多
基金financial support received from the National Key Research and Development Program of China(2022YFB3705000)the National Natural Science Foundation of China(No.52303394)the Liaoning Provincial Natural Science Foundation(No.2023-BS-015).
文摘To investigate the influence of W and Al on the microstructure and mechanical properties of a high-W superalloy,the Thermo-Calc calculation was utilized to simulate the microstructure with various W and Al contents.The results indicated that the concentration of W and Al exceeded 15.7 wt%and 5.9 wt%,respectively,the abnormal tungsten-richα-W phase would precipitate.Compared with the results of orthogonal experiment,the precipitation ofα-W phase is consistent with thermodynamic calculation results.The presence of Al not only influenced the precipitation ofα-W phase but also impacted the eutectic content and theγʹ-size,both of which showed an increase with higher Al concentrations.Excessive W and Al contents promoted the precipitation ofα-W phase,escalating the site of crack nucleation,and ultimately decreasing the plasticity.In the process of creep deformation(975℃/235 MPa),the raftedγ'phases were more continuous with increasing W contents,which increased the difficulty of dislocation climbing.As Al content increased,the density of interfacial dislocation network increased.The dislocations were entangled with each other,and the hindrance of dislocation movement was enhanced,which improved the stress rupture life.However,the precipitation of the hard and brittleα-W phase was attributed to the excessive W and Al,which increased the tendency of crack formation and significantly diminished the stress rupture life.The alloy exhibited the highest stress rupture life of 110.46 h when the W and Al contents were 15.7 wt%and 5.9 wt%,respectively.
基金supported by the National Natural Science Foundation of China(No.52303394)the National Key Research and Development Program of China(No.2022YFB3705000)+1 种基金the Natural Science Foundation of Liaoning Province(No.2023-BS-015)the Science Center for Gas Turbine Project(No.P2022-C-IV-002-001).
文摘The effect of carbon content on the microstructures and stress rupture properties of a newly developed polycrystalline Ni-based superalloy with high Cr content has been studied.It was observed that both grain size and the number of carbides increased with an increase in carbon content.After heat treatment,granular M_(23)C_(6)carbides were dispersed around MC carbides along grain boundaries and inside grains.The quantity of granular M_(23)C_(6)carbides increased while their sizes decreased.These findings can be verified with the results of thermodynamic calculation and differential scanning calorimetry analysis.The stress rupture times(975℃/225 MPa)increased from 13.3 to 25.5 h with the carbon content increased from 0.1 to 0.2 wt.%.The improvement can be attributed to two primary factors.Firstly,grain boundary is typically weak region during deformation process and the grain size increased as carbon content increased in the alloy.Secondly,carbides act as hindrances to impede dislocation movement,leading to dislocation entanglement.As carbon content rose,the quantity of carbides in interdendritic regions and grain boundaries increased,providing a certain degree of strengthening effect and resulting in a longer stress rupture time.
基金financially supported by the National Natural Science Foundation of China(Nos.51601192,51671188,51671189and 11332010)the High Technology Research and Development Program of China(No.2014AA041701)
文摘The Portevin-Le Chatelier(PLC) effects in a wrought Ni-base superalloy with different γ' precipitates contents have been investigated. Detailed analysis on the serration type of the tensile curves indicates that the γ' precipitates have a decisive influence on the transformation from normal to inverse PLC behavior, which is rarely proposed in other works. It is considered that the γ' precipitates play the same role in PLC effect as temperature and strain rate for the investigated wrought Ni-base superalloy.
基金financially supported by the State Key Lab of Advanced Metals and Materials Open Fund under Grant No.2018-Z07the National Science and Technology Major Project under Grant No.2017-VI-0002-0072+2 种基金the National Key R&D Program of China under Grant No.2017YFA0700704the National Natural Science Foundation of China(NSFC)under Grant Nos.51601192,51671188the Youth Innovation Promotion Association,Chinese Academy of Sciences
文摘The application and component designs of single crystal superalloys are restricted by the precipitation of topologically closed packed(TCP)phases,which can deteriorate the microstructural stability of the alloys severely.Limited researches concerning the type and morphology evolution of TCP phases under elevated temperature conditions have been reported previously.In the present work,three Re-containing single crystal alloys were designed to investigate TCP phase evolution via long term isothermal exposure tests at 1120℃while the effects of Re on the microstructural characteristic and elements segregation were also clarified.The results showed that the addition of Re increased the instability of the alloys and the volume fraction of the TCP phases exceeded 5 vol%when the Re content reached 3 wt%.The increasing Re content had also raised the precipitation temperature of TCP phases but it did not change the type of them after long term aging;all the TCP particles were identified asμphase in this study.Moreover,the elements segregation became considerably serious as Re addition increased constantly,which brought about various morphologies of theμphase in the experimental alloys.In particular,the rod-like and needle-likeμphases demonstrated the typical orientation withinγmatrix while the blockyμphase was dispersedly distributed in the space.No specific orientation relationship could be observed in theμphase when the addition of Re exceeded certain threshold value.
基金support received from the National Key Research and Development Program of China(2022YFB3705000)the National Natural Science Foundation of China(No.52303394)the Liaoning Provincial Natural Science Foundation(No.2023-BS-015).
文摘The formation and evolution of M_(6)C carbides in high-W superalloy following solution treatment was investigated at different temperatures.Initially,during solid solution treatment,MC and M_(6)C carbides was precipitated in the alloy.As the temperature increased,the morphology of M_(6)C carbides transitioned from granular to needle-like.During the solution treatment at 1255℃,the MC carbides degraded and transformed into M_(6)C carbides,forming a symbiotic relationship between them.Nonetheless,no clear orientation relationship was observed between the two types of carbides.After further increasing the temperature to 1270℃,the precipitation of needle-like M_(6)C carbides in the dendrite arm was confirmed.This was supported by electron probe X-ray micro-analyzer and selected area electron diffraction patterns.Subsequently,a detailed examination of the three-dimensional morphology and orientation relationship of the needle-like phase with the matrix was carried out using focused-ion-beam and transmission electron microscopy techniques.The results indicated that the flat interface of the needle phase exhibited a specific orientation relationship with the matrix.However,in the three-dimensional plane,the interfaces between the needle-like phase and the matrix were not straight.Furthermore,no clear orientation relationship between the non-straight interfaces and the matrix was observed.As the solution temperature increased,the tensile properties at room temperature progressively decreased,while the stress rupture properties peaked at 1260℃,suggesting that the alloy demonstrated its optimal comprehensive performance at this temperature.A subsequent analysis was conducted on the longitudinal section of the fracture using electron backscattered diffraction.The results showed a noticeable concentration of stress at the interface between MC and M_(6)C carbides,which ultimately led to crack initiation at this interface.In addition,as the solid solution temperature increased,the quantity of symbiotic phases also increased.This phenomenon led to the initiation of cracks at multiple locations,which then propagated and interconnected.As a consequence,the tensile properties and stress rupture life of the alloy progressively deteriorated.
基金financially supported by the National Natural Science Foundation of China(Grant No.12205055)the National Key Research and Development Program of China(Grant No.2021YFB3702500).
文摘Increasing the print quality is the critical requirement for the additive manufactured complex part of aero-engines of nickel-based superalloys.A study of the effects of Co and Nb on the crack is performed focusing on the selective laser melting(SLM)nickel-based superalloy.In this paper,the solvus temperature of γ',crack characteristics,microstructure,thermal expansion,and mechanical properties of SLM nickel-based superalloy are investigated by varying the content of Co and Nb.The alloy with 15Co/0Nb shows the highest comprehensive quality.Nb increases the crack risk and thermal deformation,and then Co accelerates the stress release.Therefore,Co is an extremely important alloying element for improving the quality of SLM nickel-based superalloy.Finally,the crack growth kinetics and the strain difference are discussed to reveal the SLM crack regular that is affected by time or temperature.The analysis work on the effect of alloying elements can obtain an effective foundational theory to guide the composition optimization of SLM nickel-based superalloys.
