The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusio...The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusion height and random position distribution of abrasive grains on the abrasive wheel surface.This study investigated the distribution of undeformed chip thickness and grinding force considering the non-uniform characteristics of abrasive wheel in the grinding of K4002 nickel-based superalloy.First,a novel grinding force model was established through a kinematic-geometric analysis and a grain-workpiece contact analysis.Then,a series of grinding experiments were conducted for verifying the model.The results indicate that the distribution of undeformed chip thickness is highly consistent with the Gaussian distribution formula.The increase in the grinding depth mainly leads to an increase in the average value of Gaussian distribution.On the contrary,the increase in the workpiece infeed speed or the decrease in the grinding speed mainly increases the standard deviation of Gaussian distribution.The average and maximum errors of the grinding force model are 4.9%and 14.6%respectively,indicating that the model is of high predication accuracy.展开更多
A new type of nickel-based single-crystal superalloy was subjected to creep performance test,microstructure observation,and composition analysis under the condition of 1100℃/140 MPa.The variation characteristics of t...A new type of nickel-based single-crystal superalloy was subjected to creep performance test,microstructure observation,and composition analysis under the condition of 1100℃/140 MPa.The variation characteristics of the creep rate during the creep fracture process and the microstructure evolution before and after creep were investigated,thereby revealing the creep fracture mechanism of the new nickel-based single-crystal superalloy.The results indicate that the creep life of the alloy is 104.5 h,and the strain can reach 33.58%.The creep rate decreases first,then increases,and finally tends to be stable until fracture.At the initial stage of creep,the creep rate decreases first,then rises and finally decreases again with time.Furthermore,the creep fracture microstructure is composed of dimples and tearing edges without obvious slip planes.Oxides and recrystallized structures exist inside the fracture surface,and the voids inside the fracture are elongated and perpendicular to the stress axis,showing a fracture mechanism of microcrack accumulation.展开更多
Laser powder bed fusion(L-PBF)is an advanced metal additive manufacturing process with an excellent capability for fabricating nickel-based superalloys.After solution aging(SA),the l-PBF nickel-based superalloys can m...Laser powder bed fusion(L-PBF)is an advanced metal additive manufacturing process with an excellent capability for fabricating nickel-based superalloys.After solution aging(SA),the l-PBF nickel-based superalloys can match the tensile properties with the conventional manufacturing process;however,its performance under long-life regime service conditions,especially at an elevated temperature of 650℃,has not yet been well understood,which restricts its promotion in industrial applications.In this study,combined with various techniques including X-ray diffraction(XRD),electron backscatter diffraction(EBSD),and micro-computed tomography(micro-CT),the microstructure,phases,micro-texture,and internal defects of SA l-PBF nickel-based superalloys were analyzed,and tensile and cutting-edge fatigue tests with stress ratios R=-1 and 0.1 were performed at 25℃ and 650℃ to investigate the fatigue failure behavior.The results showed that the SA treatment promoted microstructural homogenization with vague laser scanning tracks.The synergistic effect of the γ',γ",and δ phases improved the mechanical and fatigue properties.Elevated temperatures and positive stress ratios promoted the occurrence of subsurface or internal failures.The four cracking modes include crack nucleation from the crystallographic facets,pore-assisted facetted crack nucleation,lack of fusion-induced crack nucleation,and inclusion-induced crack nucleation.At 650℃,the grains fractured along the maximum shear plane,formed a large number of highly inhomogeneous facets,which caused significant fluctuations.Finally,the phase transition processes during SA treatment and defect-related fatigue failure mechanisms were elucidated.This study provides key quality and testing data to support the advancement of l-PBF nickel-based superalloys and provides a foundation for their optimized design and industrial applications.展开更多
The electrochemical carbon dioxide reduction reaction(CO_(2)RR)can convert carbon dioxide into highvalue chemical substances and fuels by utilizing renewable electricity,which can not only complete the carbon cycle bu...The electrochemical carbon dioxide reduction reaction(CO_(2)RR)can convert carbon dioxide into highvalue chemical substances and fuels by utilizing renewable electricity,which can not only complete the carbon cycle but also effectively alleviate the problems of global warming and energy shortage.Nickelbased catalysts hold great promise and unbeatable merits for the electroreduction of carbon dioxide due to their excellent catalytic properties and activity.However,there were few review papers on the application of nickel-based catalysts in carbon dioxide electroreduction.This paper,therefore,presents the current status of research on nickel-based catalysts in carbon dioxide electroreduction categorized by different products.First,the advantages of CO_(2) electroreduction and nickel-based catalysts as well as the basic principles of CO_(2) electroreduction are presented;then the different types of nickel-based catalysts that can convert CO_(2) into different products are described in detail,including their syntheses,performances,and mechanisms.Finally,the common features of nickel-based catalysts towards different carbon dioxide electroreduction products,as well as the outlooks for the development of nickel-based catalysts will be summarized.It is highly expected that this review will help in the future research and development of nickel-based catalysts towards CO_(2) conversion.展开更多
Nickel-based superalloys are indispensable for high-temperature engineering applications,yet their additive manufacturing(AM)is plagued by significant cracking defects.This review investigates crack failure mechanisms...Nickel-based superalloys are indispensable for high-temperature engineering applications,yet their additive manufacturing(AM)is plagued by significant cracking defects.This review investigates crack failure mechanisms in AM nickel-based superalloys,emphasizing methodologies to evaluate crack sensitivity and compositional design strategies to mitigate defects.Key crack types—solidification,liquation,solid-state,stress corrosion,fatigue,and creep-fatigue cracks—are analyzed,with focus on formation mechanisms driven by thermal gradients,solute segregation,and microstructural heterogeneities.Evaluation frameworks such as the Rappaz-Drezet-Gremaud(RDG)criterion,Solidification Cracking Index(SCI),and Strain Age Cracking(SAC)index are reviewed for predicting crack susceptibility through integration of thermodynamic parameters,solidification kinetics,and mechanical properties.Alloy compositional design strategies are presented,including optimization of strengthening elements(Al,Ti),grain boundary modifiers(B,Zr,Re),and impurity control(C,O),which suppress crack initiation and propagation via microstructure refinement and enhanced high-temperature resistance.Computational approaches,such as thermodynamically assisted design,high-throughput experimentation,and machine learning,are highlighted for decoding complex composition-structure-property relationships.Challenges in modeling multi-scale defect interactions and developing unified frameworks for manufacturing-and service-induced cracks are outlined.This review underscores the necessity of integrated computational-experimental strategies to advance reliable AM of nickel-based superalloys,providing insights for defect prediction,alloy optimization,and process control.展开更多
The GH4720Li alloy is one of the most widely used precipitation-strengthened nickel-based superalloy.However,systematic study about effect of strain rate on the plastic deformation behavior of GH4720Li alloy at interm...The GH4720Li alloy is one of the most widely used precipitation-strengthened nickel-based superalloy.However,systematic study about effect of strain rate on the plastic deformation behavior of GH4720Li alloy at intermediate temperature is lacking.The evolution of the tensile properties and plastic deformation mechanism of GH4720Li alloy with the strain rate at 650℃ were systematically studied with the help of transmission electron microscopy analysis.The results show that the tensile strength of the alloy increases and the plasticity decreases with the increase in strain rate.When the strain rate is 5 min^(-1),the tensile strength of the alloy is 1448 MPa and the tensile plasticity is 18%.As the strain rate increases from 0.05 to 0.5 min^(-1),the size and morphology of the primaryγ′phase of the alloy remain unchanged,with an average size of about 1.8μm.However,when the strain rate further increases to 5 min^(-1),the average size of the primaryγ′phase increases to 2.5μm.In addition,the increase of strain rate has no significant effect on the size and distribution of secondary and tertiaryγ′phases.As the strain rate increases from 0.05 to 5 min^(-1),the deformation mechanism of alloy gradually evolved from dislocation slip and twin to dislocation slip,indicating that the plastic deformation mechanism of the alloy presents a high strain rate sensitivity at 650℃.展开更多
Enhancing homogenization efficiency and hot-workability is the key issue for wrought superalloys in the industry.A novel approach for simultaneous accelerating the homogenization kinetics and improving hot-workability...Enhancing homogenization efficiency and hot-workability is the key issue for wrought superalloys in the industry.A novel approach for simultaneous accelerating the homogenization kinetics and improving hot-workability via a simple way of prior hot-deformation was proposed,which was not widely accepted for wrought superalloys.The homogenization efficiency is increased by 40%-70%via performing 10%-20%prior hot-deformation.Both theoretical and experimental analyses revealed that the increment in homogenization efficiency is mainly attributed to the decrease in interdendritic-segregation spacing,and thus the necessary diffusion distance,rather than that of dislocations.In addition,dynamic and static recrystallizations occurred during the prior hot-deformation and diffusion-annealing processes,and the grains were significantly refined even after the homogenization.Furthermore,the size of the precipitates was refined as well.These enhanced the hot-workability of the homogenized ingot for the subsequent cogging process.展开更多
The effects of rejuvenation heat treatment(RHT)on the serrated flow behavior and fracture mode of nickel-based superalloys(R26)were investigated by tensile tests and microstructural characterization.The serrated flow ...The effects of rejuvenation heat treatment(RHT)on the serrated flow behavior and fracture mode of nickel-based superalloys(R26)were investigated by tensile tests and microstructural characterization.The serrated flow activation energies were determined to be 41−72 and 64−81 kJ/mol before and after RHT,respectively.Dynamic strain aging in the alloy is caused by the diffusion of carbon atoms into dislocation channels in the nickel matrix.Before RHT,carbides are concentrated at the grain boundaries.Cracks initiate from these carbides and propagate along the grain boundaries.RHT dissolves carbides at grain boundaries,transferring crack initiation to the precipitated phase group in the grains.RHT increases carbon atom concentration in the nickel matrix,enhancing dynamic strain aging and serrated flow behavior.展开更多
Notable advancements have been made in the additive manufacturing(AM)of aerospace materials,driven by the needs for integrated components with intricate geometries and small-lot production of high-value components.Nic...Notable advancements have been made in the additive manufacturing(AM)of aerospace materials,driven by the needs for integrated components with intricate geometries and small-lot production of high-value components.Nickel-based superalloys,pivotal materials for high-temperature bearing components in aeroengines,present significant challenges in the fabrication of complex parts due to their great hardness.Huge attention and rapid progress have been garnered in AM processing of nicklebased superalloys,largely owing to its distinct benefits in the freedom of fabrication and reduced manufacturing lifecycle.Despite extensive research into AM in nickel-based superalloys,the corresponding results and conclusions are scattered attributed to the variety of nickel-based superalloys and complex AM processing parameters.Therefore,there is still a pressing need for a comprehensive and deep understanding of the relationship between the AM processing and microstructures and mechanical performance of nickel-based superalloys.This review introduces the processing characteristics of four primary AM technologies utilized for superalloys and summarizes the microstructures and mechanical properties prior to and post-heat treatments.Additionally,this review presents innovative superalloys specifically accommodated to AM processing and offers insights into the material development and performance improvement,aiming to provide a valuable assessment on AM processing of nickel-based superalloys and an effective guidance for the future research.展开更多
Exploring efficient transition-metal-based electrocatalysts is critical for the wide application of electrochemical hydrogen generation technology.Although the phase displays prominent influence on their performance,i...Exploring efficient transition-metal-based electrocatalysts is critical for the wide application of electrochemical hydrogen generation technology.Although the phase displays prominent influence on their performance,it remains a major challenge to achieve phase regulation in the same synthesis method and elucidate the intrinsic relationship between the phase and activity.Herein,we developed a sulfur induced electrodeposition strategy to achieve the precise phase regulation of nickel-based materials from Ni(OH)_(2)to Ni and Ni_(3)S_(2).S atoms can be introduced into Ni and Ni(OH)_(2)due to sulfur inducement,and the S proportion is finely controlled via changing the deposition parameters.Importantly,the obtained S-Ni catalyst displays enhanced hydrogen evolution activity with an ultralow overpotential of 27 mV at 10 mA cm^(-2),which is superior to the S-Ni(OH)_(2),Ni_(3)S_(2),and even Pt/C.Density functional theory(DFT)calculations disclose the S-Ni catalyst exhibits optimal charge state and local coordination,remarkably optimizing the water adsorption and Ni-H^(*)binding energy.This work provides new insights into phase regulation in electrodeposition and an understanding of the intrinsic relationship between phase and activity.展开更多
The effects of temperature and Re content on the mechanical properties,dislocation morphology,and deformation mechanism of γ-γ′phases nickel-based single crystal superalloys are investigated by using the molecular ...The effects of temperature and Re content on the mechanical properties,dislocation morphology,and deformation mechanism of γ-γ′phases nickel-based single crystal superalloys are investigated by using the molecular dynamics method through the model of γ-γ′phases containing hole defect.The addition of Re makes the dislocation distribution tend towards the γ phase.The higher the Re content,the earlier theγphase yields,while the γ′phase yields later.Dislocation bends under the combined action of the applied force and the resistance of the Re atoms to form a bend point.The Re atoms are located at the bend points and strengthen the alloy by fixing the dislocation and preventing it from cutting the γ′phase.Dislocations nucleate first in the γ phase,causing theγphase to deform plastically before the γ′phase.As the strain increases,the dislocation length first remains unchanged,then increases rapidly,and finally fluctuates and changes.The dislocation lengths in the γ phase are larger than those in the γ′phase at different temperatures.The dislocation length shows a decreasing tendency with the increase of the temperature.Temperature can affect movement of the dislocation,and superalloys have different plastic deformation mechanisms at low,medium and high temperatures.展开更多
To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas,we propose a low-cycle fatigue(LCF)life prediction model for nickel-based superalloys using a data augmentation me...To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas,we propose a low-cycle fatigue(LCF)life prediction model for nickel-based superalloys using a data augmentation method.This method utilizes a variational autoencoder(VAE)to generate low-cycle fatigue data and form an augmented dataset.The Pearson correlation coefficient(PCC)is employed to verify the similarity of feature distributions between the original and augmented datasets.Six machine learning models,namely random forest(RF),artificial neural network(ANN),support vector machine(SVM),gradient-boosted decision tree(GBDT),eXtreme Gradient Boosting(XGBoost),and Categorical Boosting(CatBoost),are utilized to predict the LCF life of nickel-based superalloys.Results indicate that the proposed data augmentation method based on VAE can effectively expand the dataset,and the mean absolute error(MAE),root mean square error(RMSE),and R-squared(R^(2))values achieved using the CatBoost model,with respective values of 0.0242,0.0391,and 0.9538,are superior to those of the other models.The proposed method reduces the cost and time associated with LCF experiments and accurately establishes the relationship between fatigue characteristics and LCF life of nickel-based superalloys.展开更多
Quantifying the residual stress at micron-scale is crucial for comprehending the trans-and inter-granular deformation mechanisms and the influence of heat treatment,but remains technically challenging.This study utili...Quantifying the residual stress at micron-scale is crucial for comprehending the trans-and inter-granular deformation mechanisms and the influence of heat treatment,but remains technically challenging.This study utilized focused ion beam and digital image correlation(FIB-DIC)techniques to assess residual stress within the dendrite stem and arm of nickel-based single-crystal superalloys.The influence of hot isostatic pressing(HIP)on the microstructure and residual stress was also elucidated.Our results revealed that the residual stresses in the dendrite stem and arm regions manifest as tensile stress along the x-axis and compressive stress along the y-axis,with a range of−720 MPa to 680 MPa.HIP treatment effectively improved microstructure and regulated residual stress in nickel-based single-crystal superalloys,leading to a rapid reduction in residual stress levels.The present study lays a solid theoretical groundwork for optimizing processing strategies to regulate residual stress and enhance mechanical properties in next-generation single-crystal superalloys.展开更多
Inclusions in nickel-based superalloys significantly influence their mechanical properties which limit the application and development.A two-dimensional axisymmetric model coupling electromagnetic flow,heat transfer,a...Inclusions in nickel-based superalloys significantly influence their mechanical properties which limit the application and development.A two-dimensional axisymmetric model coupling electromagnetic flow,heat transfer,and inclusions transport was developed using the finite element method.The effects of current intensity and frequency on the transport behavior of inclusions and removal rate during vacuum induction melting were investigated using this model.To verify the accuracy of the mathematical model,experiments were conducted using the vacuum induction furnace model VIF200.A comparison of the experimental results with the simulation results reveals an excellent agreement.Four eddies exist in the central section of the molten pool,with any two eddies flowing in opposite directions.The drag force exerted by the eddies causes the inclusions converge toward the four corners of the cut surface.Due to buoyancy,an increase in the particle size of inclusions makes it easier for them to be adsorbed by the free surface,a phenomenon that is particularly noticeable for inclusions with a particle size of 400μm.An increase in current intensity changes the adsorption interface of certain 400-μm inclusions from the free surface to the sidewall.Increasing both current intensity and frequency enhances the crucible removal rate of inclusions,with current intensity exerting a more significant effect,increasing the removal rate by approximately 1% for every 150 A.Upon completion of melting,the ingot is typically obtained by pouring or bottom pouring,and inclusions adsorbed to the free surface are difficult to separate.Therefore,higher current intensity and frequency should be employed during melting to enhance the crucible removal rate.展开更多
The mechanical properties and oxidation resistance of two nickel-based superalloys with and without oxide dispersion strengthened(ODS)phases at different temperatures were studied.The microstructure was investigated b...The mechanical properties and oxidation resistance of two nickel-based superalloys with and without oxide dispersion strengthened(ODS)phases at different temperatures were studied.The microstructure was investigated by scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).The results show that the yield strength of the samples with and without ODS phases at room temperature is 1020 and 324 MPa,respectively.The yield strength model was constructed,and it is found that the contribution of grain boundary strengthening,dislocation strengthening and nanoparticle strengthening of nickel-based ODS superalloy exceeds 83%.As the temperature increases,grain boundary sliding and migration decrease the strength of sample but improve its ductility.Oxidation hinders the ductility of sample and intensifies its fracture,and the maximum elongation of nickel-based ODS superalloy at 800℃ is 47.3%.展开更多
In this work,we coated a layer of Y_(2)O_(3) particles in Hastelloy X(HX)nickel-based superalloy powder by in situ chemical method and combined with laser powder bed fusion(LPBF)technology to develop a high-performanc...In this work,we coated a layer of Y_(2)O_(3) particles in Hastelloy X(HX)nickel-based superalloy powder by in situ chemical method and combined with laser powder bed fusion(LPBF)technology to develop a high-performance Y_(2)O_(3)-doping alloy,designated as Y-HX.The results show that the doping of Y_(2)O_(3) particles prevents crack formation during the printing process and reduces solute segregation at cell and grain boundaries by increasing the viscosity of the molten pool.The doping of Y_(2)O_(3) particles to the printed Y-HX alloy enhances grain boundary characteristics,transforming coarse sheet-like carbides into finely dispersed granular carbides at the boundaries during subsequent heat treatment.Additionally,doping with Y_(2)O_(3) particles increases the recrystallization activation energy of the Y-HX alloy from 149.4 to 278.8 kJ mol^(-1).At 750℃,the Y-HX alloy exhibits an ultimate tensile strength of 619±2 MPa and an elongation of 52%±2%,along with an ultimate tensile strength of 325±3 MPa and an elongation of 47%±2% at 900℃.Our work provides a promising way to develop additive-manufactured superalloys with exceptional thermal stability and remarkable high-temperature mechanical properties.展开更多
For nickel-based superalloys with medium volume-fractionγʹphase(20%-40%),dual or multi-stage aging treatments are usually conducted to generate a microstructure containing the multimodal distri-bution ofγʹfor a bala...For nickel-based superalloys with medium volume-fractionγʹphase(20%-40%),dual or multi-stage aging treatments are usually conducted to generate a microstructure containing the multimodal distri-bution ofγʹfor a balance of strength and plasticity.In the present study,the microstructure and high-temperature properties of a novel cast nickel-based superalloy K4800 were investigated after being sub-jected to three heat treatments(HT)procedures,namely HT1:1180℃/4 h+1090℃/2 h+800℃/16 h,HT2:1180℃/4 h+1060℃/2 h+800℃/16 h and HT3:1180℃/4 h+800℃/16 h.It was found that the sub-solvus aging treatments at 1090 and 1060℃ precipitated sub-micron-sized(∼300 nm)primaryγʹphase which enhanced the ductility during 800℃ tensile(the total elongation of T1,T2,and T3 sam-ples were 6.75%,7.3%,and 3.25%,respectively)without evidently impairing the strength.After careful microstructure observation and deformation mechanism analysis,the enhancement of elongation was ra-tionalized that the precipitation of the sub-micron-sized primaryγʹphase decreased the volume-fraction and size of the nanometer-sizedγʹphase which was precipitated at 800℃,and simultaneously,pro-moted the dislocation movement by suppressing the non-planar slip.However,an excessive amount of the sub-micron-sized primaryγʹphase led to a faster ripening process of the nanometer-sizedγʹduring creep,which decreased the creep life at 800℃/430 MPa(T1:125 h,T2:199 h,and T3:198 h).Based on this,we monitored the number density of nanometer-sizedγʹphase coexisting with different amounts of largeγʹduring creep.An area fraction less than 7%of the sub-micron-sizedγʹphase was considered to have little detrimental effect on the creep life of K4800 alloy,which corresponded to a sub-solvus temperature range about 1080-1090℃.展开更多
In this paper,the effects of rare earth oxides on the micro structure and mechanical properties of nickelbased superalloys prepared by high-energy beam processing technology were critically studied.The focus is on the...In this paper,the effects of rare earth oxides on the micro structure and mechanical properties of nickelbased superalloys prepared by high-energy beam processing technology were critically studied.The focus is on the optimal amount of rare earth oxides that can produce ideal results.Special attention was paid to their main strengthening mechanisms,including solid solution strengthening mainly in the form of solid solution dissolved in the nickel-based alloy and improving the microstructure of the alloy by grain refinement or fine grain strengthening produced by homogenizing the distribution phase.Y_(2)O_(3),La_(2)O_(3) and CeO_(2) rare earth oxides can also improve the fluidity of the alloy molten pool and reduce the segregation of alloying elements.These advantages can significantly improve the mechanical properties of the alloy.Thereafter,this paper outlines the future research directions of rare earth oxides,aiming to expand their application potential.展开更多
Rare-earth elements(REEs)received special attention and widespread application because of their extremely active chemical property.Many researches demonstrated that doping of REEs(Y,La and Ce)in superalloys can signif...Rare-earth elements(REEs)received special attention and widespread application because of their extremely active chemical property.Many researches demonstrated that doping of REEs(Y,La and Ce)in superalloys can significantly improve the high temperature oxidation resistance,corrosion resistance and mechanical properties,which are recognized as a promising route to broaden the manufacturing process window and enhance the overall performance of next-generation superalloys.The first part of this review described the special behavior of REEs during the metallurgical solidification process,including the REEs loss in the melt and the macro-segregation phenomenon.The second part summarized a broad spectrum of works reporting the dual role of REEs addition on the mechanical properties of superalloys.The third part overviewed the effect of REEs on the anti-oxidation resistance of the fourth and fifth nickel-based superalloys.Finally,the prospect of development of REEs-containing superalloys was discussed.展开更多
For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical a...For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure.In this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the DMWs.Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization.By applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of DMW.The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ interface.The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries.The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking.It is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415 and 52205475)the Science Center for Gas Turbine Project(Nos.P2022-AB-Ⅳ-002-001 and P2023-B-Ⅳ-003-001)+3 种基金the Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology(No.JSKL2223K01)the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Superior Postdoctoral Project of Jiangsu Province(No.2022ZB215)the Henan Science and Technology Public Relations Project(No.212102210445).
文摘The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusion height and random position distribution of abrasive grains on the abrasive wheel surface.This study investigated the distribution of undeformed chip thickness and grinding force considering the non-uniform characteristics of abrasive wheel in the grinding of K4002 nickel-based superalloy.First,a novel grinding force model was established through a kinematic-geometric analysis and a grain-workpiece contact analysis.Then,a series of grinding experiments were conducted for verifying the model.The results indicate that the distribution of undeformed chip thickness is highly consistent with the Gaussian distribution formula.The increase in the grinding depth mainly leads to an increase in the average value of Gaussian distribution.On the contrary,the increase in the workpiece infeed speed or the decrease in the grinding speed mainly increases the standard deviation of Gaussian distribution.The average and maximum errors of the grinding force model are 4.9%and 14.6%respectively,indicating that the model is of high predication accuracy.
基金China Postdoctoral Science Foundation General Project(2024M760034)Postdoctoral Research Programs of Anhui Province(2024A774)。
文摘A new type of nickel-based single-crystal superalloy was subjected to creep performance test,microstructure observation,and composition analysis under the condition of 1100℃/140 MPa.The variation characteristics of the creep rate during the creep fracture process and the microstructure evolution before and after creep were investigated,thereby revealing the creep fracture mechanism of the new nickel-based single-crystal superalloy.The results indicate that the creep life of the alloy is 104.5 h,and the strain can reach 33.58%.The creep rate decreases first,then increases,and finally tends to be stable until fracture.At the initial stage of creep,the creep rate decreases first,then rises and finally decreases again with time.Furthermore,the creep fracture microstructure is composed of dimples and tearing edges without obvious slip planes.Oxides and recrystallized structures exist inside the fracture surface,and the voids inside the fracture are elongated and perpendicular to the stress axis,showing a fracture mechanism of microcrack accumulation.
基金supported by National Natural Science Foundation of China(Grant No.52175128)the State Key Laboratory for the Mechanical Behavior of Materials of China(Grant No.20232501).
文摘Laser powder bed fusion(L-PBF)is an advanced metal additive manufacturing process with an excellent capability for fabricating nickel-based superalloys.After solution aging(SA),the l-PBF nickel-based superalloys can match the tensile properties with the conventional manufacturing process;however,its performance under long-life regime service conditions,especially at an elevated temperature of 650℃,has not yet been well understood,which restricts its promotion in industrial applications.In this study,combined with various techniques including X-ray diffraction(XRD),electron backscatter diffraction(EBSD),and micro-computed tomography(micro-CT),the microstructure,phases,micro-texture,and internal defects of SA l-PBF nickel-based superalloys were analyzed,and tensile and cutting-edge fatigue tests with stress ratios R=-1 and 0.1 were performed at 25℃ and 650℃ to investigate the fatigue failure behavior.The results showed that the SA treatment promoted microstructural homogenization with vague laser scanning tracks.The synergistic effect of the γ',γ",and δ phases improved the mechanical and fatigue properties.Elevated temperatures and positive stress ratios promoted the occurrence of subsurface or internal failures.The four cracking modes include crack nucleation from the crystallographic facets,pore-assisted facetted crack nucleation,lack of fusion-induced crack nucleation,and inclusion-induced crack nucleation.At 650℃,the grains fractured along the maximum shear plane,formed a large number of highly inhomogeneous facets,which caused significant fluctuations.Finally,the phase transition processes during SA treatment and defect-related fatigue failure mechanisms were elucidated.This study provides key quality and testing data to support the advancement of l-PBF nickel-based superalloys and provides a foundation for their optimized design and industrial applications.
文摘The electrochemical carbon dioxide reduction reaction(CO_(2)RR)can convert carbon dioxide into highvalue chemical substances and fuels by utilizing renewable electricity,which can not only complete the carbon cycle but also effectively alleviate the problems of global warming and energy shortage.Nickelbased catalysts hold great promise and unbeatable merits for the electroreduction of carbon dioxide due to their excellent catalytic properties and activity.However,there were few review papers on the application of nickel-based catalysts in carbon dioxide electroreduction.This paper,therefore,presents the current status of research on nickel-based catalysts in carbon dioxide electroreduction categorized by different products.First,the advantages of CO_(2) electroreduction and nickel-based catalysts as well as the basic principles of CO_(2) electroreduction are presented;then the different types of nickel-based catalysts that can convert CO_(2) into different products are described in detail,including their syntheses,performances,and mechanisms.Finally,the common features of nickel-based catalysts towards different carbon dioxide electroreduction products,as well as the outlooks for the development of nickel-based catalysts will be summarized.It is highly expected that this review will help in the future research and development of nickel-based catalysts towards CO_(2) conversion.
基金supported by the Aero Engine Corporation of China[Grant No.HFZL2022CXY029]the Young Elite Scientists Sponsorship Programby CAST[2022QNRC001]the High Performance Computing Center of Central South University,and the Project Supported by State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China。
文摘Nickel-based superalloys are indispensable for high-temperature engineering applications,yet their additive manufacturing(AM)is plagued by significant cracking defects.This review investigates crack failure mechanisms in AM nickel-based superalloys,emphasizing methodologies to evaluate crack sensitivity and compositional design strategies to mitigate defects.Key crack types—solidification,liquation,solid-state,stress corrosion,fatigue,and creep-fatigue cracks—are analyzed,with focus on formation mechanisms driven by thermal gradients,solute segregation,and microstructural heterogeneities.Evaluation frameworks such as the Rappaz-Drezet-Gremaud(RDG)criterion,Solidification Cracking Index(SCI),and Strain Age Cracking(SAC)index are reviewed for predicting crack susceptibility through integration of thermodynamic parameters,solidification kinetics,and mechanical properties.Alloy compositional design strategies are presented,including optimization of strengthening elements(Al,Ti),grain boundary modifiers(B,Zr,Re),and impurity control(C,O),which suppress crack initiation and propagation via microstructure refinement and enhanced high-temperature resistance.Computational approaches,such as thermodynamically assisted design,high-throughput experimentation,and machine learning,are highlighted for decoding complex composition-structure-property relationships.Challenges in modeling multi-scale defect interactions and developing unified frameworks for manufacturing-and service-induced cracks are outlined.This review underscores the necessity of integrated computational-experimental strategies to advance reliable AM of nickel-based superalloys,providing insights for defect prediction,alloy optimization,and process control.
基金supported by the National Natural Science Foundation of China(52074092)National Science and Technology Major Project of China(J2019-VI-0006-0120).
文摘The GH4720Li alloy is one of the most widely used precipitation-strengthened nickel-based superalloy.However,systematic study about effect of strain rate on the plastic deformation behavior of GH4720Li alloy at intermediate temperature is lacking.The evolution of the tensile properties and plastic deformation mechanism of GH4720Li alloy with the strain rate at 650℃ were systematically studied with the help of transmission electron microscopy analysis.The results show that the tensile strength of the alloy increases and the plasticity decreases with the increase in strain rate.When the strain rate is 5 min^(-1),the tensile strength of the alloy is 1448 MPa and the tensile plasticity is 18%.As the strain rate increases from 0.05 to 0.5 min^(-1),the size and morphology of the primaryγ′phase of the alloy remain unchanged,with an average size of about 1.8μm.However,when the strain rate further increases to 5 min^(-1),the average size of the primaryγ′phase increases to 2.5μm.In addition,the increase of strain rate has no significant effect on the size and distribution of secondary and tertiaryγ′phases.As the strain rate increases from 0.05 to 5 min^(-1),the deformation mechanism of alloy gradually evolved from dislocation slip and twin to dislocation slip,indicating that the plastic deformation mechanism of the alloy presents a high strain rate sensitivity at 650℃.
基金supported by the National Natural Science Foundation of China(No.51804232)Beijing Municipal Natural Science Foundation(No.2212041)+1 种基金supported by the Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities)(FRF-IDRY-20-020)GIMRT Program of the Institute for Materials Research,Tohoku University(202303-RDKGE-0518).
文摘Enhancing homogenization efficiency and hot-workability is the key issue for wrought superalloys in the industry.A novel approach for simultaneous accelerating the homogenization kinetics and improving hot-workability via a simple way of prior hot-deformation was proposed,which was not widely accepted for wrought superalloys.The homogenization efficiency is increased by 40%-70%via performing 10%-20%prior hot-deformation.Both theoretical and experimental analyses revealed that the increment in homogenization efficiency is mainly attributed to the decrease in interdendritic-segregation spacing,and thus the necessary diffusion distance,rather than that of dislocations.In addition,dynamic and static recrystallizations occurred during the prior hot-deformation and diffusion-annealing processes,and the grains were significantly refined even after the homogenization.Furthermore,the size of the precipitates was refined as well.These enhanced the hot-workability of the homogenized ingot for the subsequent cogging process.
基金supported by the National Natural Science Foundation of China(No.52175286)the Tribology Science Fund of State Key Laboratory of Tribology in Advanced Equipment,Tsinghua University,China(No.SKLTKF20B16).
文摘The effects of rejuvenation heat treatment(RHT)on the serrated flow behavior and fracture mode of nickel-based superalloys(R26)were investigated by tensile tests and microstructural characterization.The serrated flow activation energies were determined to be 41−72 and 64−81 kJ/mol before and after RHT,respectively.Dynamic strain aging in the alloy is caused by the diffusion of carbon atoms into dislocation channels in the nickel matrix.Before RHT,carbides are concentrated at the grain boundaries.Cracks initiate from these carbides and propagate along the grain boundaries.RHT dissolves carbides at grain boundaries,transferring crack initiation to the precipitated phase group in the grains.RHT increases carbon atom concentration in the nickel matrix,enhancing dynamic strain aging and serrated flow behavior.
基金financially supported by the National Key R&D Program of China(No.2021YFB3702301)the National Natural Science Foundation of China(No.52101068]+2 种基金the China Postdoctoral Science Foundation[No.2022T150342]the Postdoctoral International Exchange Program[No.YJ20210129]the Shuimu Tsinghua Scholar Program(No.2020SM100)
文摘Notable advancements have been made in the additive manufacturing(AM)of aerospace materials,driven by the needs for integrated components with intricate geometries and small-lot production of high-value components.Nickel-based superalloys,pivotal materials for high-temperature bearing components in aeroengines,present significant challenges in the fabrication of complex parts due to their great hardness.Huge attention and rapid progress have been garnered in AM processing of nicklebased superalloys,largely owing to its distinct benefits in the freedom of fabrication and reduced manufacturing lifecycle.Despite extensive research into AM in nickel-based superalloys,the corresponding results and conclusions are scattered attributed to the variety of nickel-based superalloys and complex AM processing parameters.Therefore,there is still a pressing need for a comprehensive and deep understanding of the relationship between the AM processing and microstructures and mechanical performance of nickel-based superalloys.This review introduces the processing characteristics of four primary AM technologies utilized for superalloys and summarizes the microstructures and mechanical properties prior to and post-heat treatments.Additionally,this review presents innovative superalloys specifically accommodated to AM processing and offers insights into the material development and performance improvement,aiming to provide a valuable assessment on AM processing of nickel-based superalloys and an effective guidance for the future research.
基金supported by the National Natural Science Foundation of China(52271210,22179032,52171176)。
文摘Exploring efficient transition-metal-based electrocatalysts is critical for the wide application of electrochemical hydrogen generation technology.Although the phase displays prominent influence on their performance,it remains a major challenge to achieve phase regulation in the same synthesis method and elucidate the intrinsic relationship between the phase and activity.Herein,we developed a sulfur induced electrodeposition strategy to achieve the precise phase regulation of nickel-based materials from Ni(OH)_(2)to Ni and Ni_(3)S_(2).S atoms can be introduced into Ni and Ni(OH)_(2)due to sulfur inducement,and the S proportion is finely controlled via changing the deposition parameters.Importantly,the obtained S-Ni catalyst displays enhanced hydrogen evolution activity with an ultralow overpotential of 27 mV at 10 mA cm^(-2),which is superior to the S-Ni(OH)_(2),Ni_(3)S_(2),and even Pt/C.Density functional theory(DFT)calculations disclose the S-Ni catalyst exhibits optimal charge state and local coordination,remarkably optimizing the water adsorption and Ni-H^(*)binding energy.This work provides new insights into phase regulation in electrodeposition and an understanding of the intrinsic relationship between phase and activity.
基金Project supported by the Xi’an Science and Technology Plan Project of Shaanxi Province of China(Grant No.23GXFW0086).
文摘The effects of temperature and Re content on the mechanical properties,dislocation morphology,and deformation mechanism of γ-γ′phases nickel-based single crystal superalloys are investigated by using the molecular dynamics method through the model of γ-γ′phases containing hole defect.The addition of Re makes the dislocation distribution tend towards the γ phase.The higher the Re content,the earlier theγphase yields,while the γ′phase yields later.Dislocation bends under the combined action of the applied force and the resistance of the Re atoms to form a bend point.The Re atoms are located at the bend points and strengthen the alloy by fixing the dislocation and preventing it from cutting the γ′phase.Dislocations nucleate first in the γ phase,causing theγphase to deform plastically before the γ′phase.As the strain increases,the dislocation length first remains unchanged,then increases rapidly,and finally fluctuates and changes.The dislocation lengths in the γ phase are larger than those in the γ′phase at different temperatures.The dislocation length shows a decreasing tendency with the increase of the temperature.Temperature can affect movement of the dislocation,and superalloys have different plastic deformation mechanisms at low,medium and high temperatures.
基金Financial support from the Fundamental Research Funds for the Central Universities(ZJ2022-003,JG2022-27,J2020-060,and J2021-060)Sichuan Province Engineering Technology Research Center of General Aircraft Maintenance(GAMRC2021YB08)the Young Scientists Fund of the National Natural Science Foundation of China(No.52105417)is acknowledged.
文摘To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas,we propose a low-cycle fatigue(LCF)life prediction model for nickel-based superalloys using a data augmentation method.This method utilizes a variational autoencoder(VAE)to generate low-cycle fatigue data and form an augmented dataset.The Pearson correlation coefficient(PCC)is employed to verify the similarity of feature distributions between the original and augmented datasets.Six machine learning models,namely random forest(RF),artificial neural network(ANN),support vector machine(SVM),gradient-boosted decision tree(GBDT),eXtreme Gradient Boosting(XGBoost),and Categorical Boosting(CatBoost),are utilized to predict the LCF life of nickel-based superalloys.Results indicate that the proposed data augmentation method based on VAE can effectively expand the dataset,and the mean absolute error(MAE),root mean square error(RMSE),and R-squared(R^(2))values achieved using the CatBoost model,with respective values of 0.0242,0.0391,and 0.9538,are superior to those of the other models.The proposed method reduces the cost and time associated with LCF experiments and accurately establishes the relationship between fatigue characteristics and LCF life of nickel-based superalloys.
基金financially supported by the National Key Research&Development Plan(No.2020YFA0405900)the National Natural Science Foundation of China(Nos.52171117,52371113,and 92263201)+1 种基金the Tuoyuan Project of Nanjing Tech University(No.20230113)the Technological Projects from CRCC Qishuyan Institute Co.,LTD(No.BS24125).
文摘Quantifying the residual stress at micron-scale is crucial for comprehending the trans-and inter-granular deformation mechanisms and the influence of heat treatment,but remains technically challenging.This study utilized focused ion beam and digital image correlation(FIB-DIC)techniques to assess residual stress within the dendrite stem and arm of nickel-based single-crystal superalloys.The influence of hot isostatic pressing(HIP)on the microstructure and residual stress was also elucidated.Our results revealed that the residual stresses in the dendrite stem and arm regions manifest as tensile stress along the x-axis and compressive stress along the y-axis,with a range of−720 MPa to 680 MPa.HIP treatment effectively improved microstructure and regulated residual stress in nickel-based single-crystal superalloys,leading to a rapid reduction in residual stress levels.The present study lays a solid theoretical groundwork for optimizing processing strategies to regulate residual stress and enhance mechanical properties in next-generation single-crystal superalloys.
基金financially supported by the National Natural Science Foundation of China(Nos.52422408 and 52171031)Excellent Youth Fund of Liaoning Natural Science Foundation(No.2023JH3/10200001)Liaoning Xingliao Talents-Top-notch Young Talents Project(No.XLYC2203064).
文摘Inclusions in nickel-based superalloys significantly influence their mechanical properties which limit the application and development.A two-dimensional axisymmetric model coupling electromagnetic flow,heat transfer,and inclusions transport was developed using the finite element method.The effects of current intensity and frequency on the transport behavior of inclusions and removal rate during vacuum induction melting were investigated using this model.To verify the accuracy of the mathematical model,experiments were conducted using the vacuum induction furnace model VIF200.A comparison of the experimental results with the simulation results reveals an excellent agreement.Four eddies exist in the central section of the molten pool,with any two eddies flowing in opposite directions.The drag force exerted by the eddies causes the inclusions converge toward the four corners of the cut surface.Due to buoyancy,an increase in the particle size of inclusions makes it easier for them to be adsorbed by the free surface,a phenomenon that is particularly noticeable for inclusions with a particle size of 400μm.An increase in current intensity changes the adsorption interface of certain 400-μm inclusions from the free surface to the sidewall.Increasing both current intensity and frequency enhances the crucible removal rate of inclusions,with current intensity exerting a more significant effect,increasing the removal rate by approximately 1% for every 150 A.Upon completion of melting,the ingot is typically obtained by pouring or bottom pouring,and inclusions adsorbed to the free surface are difficult to separate.Therefore,higher current intensity and frequency should be employed during melting to enhance the crucible removal rate.
基金supported by the National Natural Science Foundation of China(No.52271177)Leading Talents Project of Scientific and Technological Innovation in Hunan Province,China(No.2021RC4036)+1 种基金the Natural Science Foundation of Hunan Province,China(Nos.2023JJ50172,2020JJ6069)State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology,China。
文摘The mechanical properties and oxidation resistance of two nickel-based superalloys with and without oxide dispersion strengthened(ODS)phases at different temperatures were studied.The microstructure was investigated by scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).The results show that the yield strength of the samples with and without ODS phases at room temperature is 1020 and 324 MPa,respectively.The yield strength model was constructed,and it is found that the contribution of grain boundary strengthening,dislocation strengthening and nanoparticle strengthening of nickel-based ODS superalloy exceeds 83%.As the temperature increases,grain boundary sliding and migration decrease the strength of sample but improve its ductility.Oxidation hinders the ductility of sample and intensifies its fracture,and the maximum elongation of nickel-based ODS superalloy at 800℃ is 47.3%.
基金the National Key R&D Program of China(No.2023YFB3712002)the National Natural Science Founda-tion of China(Grant Nos.U22A20172 and 52171044)the Seed Foundation of Tianjin University(Grant No.2023XZL-0015).
文摘In this work,we coated a layer of Y_(2)O_(3) particles in Hastelloy X(HX)nickel-based superalloy powder by in situ chemical method and combined with laser powder bed fusion(LPBF)technology to develop a high-performance Y_(2)O_(3)-doping alloy,designated as Y-HX.The results show that the doping of Y_(2)O_(3) particles prevents crack formation during the printing process and reduces solute segregation at cell and grain boundaries by increasing the viscosity of the molten pool.The doping of Y_(2)O_(3) particles to the printed Y-HX alloy enhances grain boundary characteristics,transforming coarse sheet-like carbides into finely dispersed granular carbides at the boundaries during subsequent heat treatment.Additionally,doping with Y_(2)O_(3) particles increases the recrystallization activation energy of the Y-HX alloy from 149.4 to 278.8 kJ mol^(-1).At 750℃,the Y-HX alloy exhibits an ultimate tensile strength of 619±2 MPa and an elongation of 52%±2%,along with an ultimate tensile strength of 325±3 MPa and an elongation of 47%±2% at 900℃.Our work provides a promising way to develop additive-manufactured superalloys with exceptional thermal stability and remarkable high-temperature mechanical properties.
文摘For nickel-based superalloys with medium volume-fractionγʹphase(20%-40%),dual or multi-stage aging treatments are usually conducted to generate a microstructure containing the multimodal distri-bution ofγʹfor a balance of strength and plasticity.In the present study,the microstructure and high-temperature properties of a novel cast nickel-based superalloy K4800 were investigated after being sub-jected to three heat treatments(HT)procedures,namely HT1:1180℃/4 h+1090℃/2 h+800℃/16 h,HT2:1180℃/4 h+1060℃/2 h+800℃/16 h and HT3:1180℃/4 h+800℃/16 h.It was found that the sub-solvus aging treatments at 1090 and 1060℃ precipitated sub-micron-sized(∼300 nm)primaryγʹphase which enhanced the ductility during 800℃ tensile(the total elongation of T1,T2,and T3 sam-ples were 6.75%,7.3%,and 3.25%,respectively)without evidently impairing the strength.After careful microstructure observation and deformation mechanism analysis,the enhancement of elongation was ra-tionalized that the precipitation of the sub-micron-sized primaryγʹphase decreased the volume-fraction and size of the nanometer-sizedγʹphase which was precipitated at 800℃,and simultaneously,pro-moted the dislocation movement by suppressing the non-planar slip.However,an excessive amount of the sub-micron-sized primaryγʹphase led to a faster ripening process of the nanometer-sizedγʹduring creep,which decreased the creep life at 800℃/430 MPa(T1:125 h,T2:199 h,and T3:198 h).Based on this,we monitored the number density of nanometer-sizedγʹphase coexisting with different amounts of largeγʹduring creep.An area fraction less than 7%of the sub-micron-sizedγʹphase was considered to have little detrimental effect on the creep life of K4800 alloy,which corresponded to a sub-solvus temperature range about 1080-1090℃.
基金Project supported by China Postdoctoral Science Foundation(2021M7010380)the Natural Science Foundation of Shanghai (20ZR1422700)Class Ⅲ Peak Discipline of Shanghai-Materials Science and Engineering (High-Energy Beam Intelligent Processing and Green Manufacturing)。
文摘In this paper,the effects of rare earth oxides on the micro structure and mechanical properties of nickelbased superalloys prepared by high-energy beam processing technology were critically studied.The focus is on the optimal amount of rare earth oxides that can produce ideal results.Special attention was paid to their main strengthening mechanisms,including solid solution strengthening mainly in the form of solid solution dissolved in the nickel-based alloy and improving the microstructure of the alloy by grain refinement or fine grain strengthening produced by homogenizing the distribution phase.Y_(2)O_(3),La_(2)O_(3) and CeO_(2) rare earth oxides can also improve the fluidity of the alloy molten pool and reduce the segregation of alloying elements.These advantages can significantly improve the mechanical properties of the alloy.Thereafter,this paper outlines the future research directions of rare earth oxides,aiming to expand their application potential.
基金supported by the National Science and Technology Major Project(Nos.J2019-VI-0023-0139 and J2019-VII-0004-0144)the National Key R&D Program of China(No.2020YFA0714904).
文摘Rare-earth elements(REEs)received special attention and widespread application because of their extremely active chemical property.Many researches demonstrated that doping of REEs(Y,La and Ce)in superalloys can significantly improve the high temperature oxidation resistance,corrosion resistance and mechanical properties,which are recognized as a promising route to broaden the manufacturing process window and enhance the overall performance of next-generation superalloys.The first part of this review described the special behavior of REEs during the metallurgical solidification process,including the REEs loss in the melt and the macro-segregation phenomenon.The second part summarized a broad spectrum of works reporting the dual role of REEs addition on the mechanical properties of superalloys.The third part overviewed the effect of REEs on the anti-oxidation resistance of the fourth and fifth nickel-based superalloys.Finally,the prospect of development of REEs-containing superalloys was discussed.
基金Supported by Youth Elite Project of CNNC and Modular HTGR Super-critical Power Generation Technology Collaborative Project between CNNC and Tsinghua University Project of China(Grant No.ZHJTIZYFGWD20201).
文摘For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure.In this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the DMWs.Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization.By applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of DMW.The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ interface.The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries.The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking.It is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.
