Medium-entropy alloys(MEAs)that exhibit transformation-induced plasticity(TRIP)from face-centered cubic(FCC)to body-centered cubic(BCC)are considered promising for liquid hydrogen environments due to their remarkable ...Medium-entropy alloys(MEAs)that exhibit transformation-induced plasticity(TRIP)from face-centered cubic(FCC)to body-centered cubic(BCC)are considered promising for liquid hydrogen environments due to their remarkable cryogenic strength.Nonetheless,studies on hydrogen embrittlement(HE)in BCC-TRIP MEAs have not been conducted,although the TRIP effect and consequent BCC martensite usually deteriorate HE susceptibility.In these alloys,initial as-quenched martensite alters hydrogen diffusion and trap behavior,and deformation-induced martensitic transformation(DIMT)provides preferred crack propagation sites,which critically affects HE susceptibility.Therefore,this study aims to investigate the HE behav-ior of BCC-TRIP MEAs by designing four V10 Cr_(10)Co_(30)Fe_(50-x)Ni_(x)(x=0,1,2,and 3 at%)MEAs,adjusting both the initial phase constituent and phase metastability.A decreased Ni content leads to a reduced fraction and mechanical stability of FCC,which in turn increases HE susceptibility,as determined through electro-chemical hydrogen pre-charging and slow-strain rate tests The permeation test and thermal desorption analysis reveal that the hydrogen diffusivity and content are affected by initial BCC fraction,interconnectivity of BCC,and refined FCC.As these initial phase constituents differ between the alloys with FCC-and BCC-dominant initial phase,microstructural factors affecting HE are unveiled discretely among these alloy groups by correlation of hydrogen-induced crack behavior with hydrogen diffusion and trap behavior.In alloys with an FCC-dominant initial phase,the initial BCC fraction and DIMT initiation rate emerge as critical factors,rather than the extent of DIMT.For BCC-dominant alloys,the primary contributor is an increase in the initial BCC fraction,rather than the extent or rate of DIMT.The unraveled roles of microstructural factors provide insights into designing HE-resistant BCC-TRIP MEAs.展开更多
The dynamics of phase separation in H–He binary systems within gas giants such as Jupiter and Saturn exhibit remarkable complexity, yet lack systematic investigation. Through large-scale machine-learning-accelerated ...The dynamics of phase separation in H–He binary systems within gas giants such as Jupiter and Saturn exhibit remarkable complexity, yet lack systematic investigation. Through large-scale machine-learning-accelerated molecular dynamics simulations spanning broad temperature-pressure-composition(2000–10000 K, 1–7 Mbar,pure H to pure He) regimes, we systematically determine self and mutual diffusion coefficients in H–He systems and establish a six-dimensional framework correlating temperature, pressure, helium abundance, phase separation degree, diffusion coefficients, and anisotropy. Key findings reveal that hydrogen exhibits active directional migration with pronounced diffusion anisotropy, whereas helium passively aggregates in response. While the conventional mixing rule underestimates mutual diffusion coefficients by neglecting velocity cross-correlations,the assumption of an ideal thermodynamic factor(Q = 1) overestimates them due to unaccounted non-ideal thermodynamic effects—both particularly pronounced in strongly phase-separated regimes. Notably, hydrogen's dual role, anisotropic diffusion and bond stabilization via helium doping, modulates demixing kinetics. Large-scale simulations(216,000 atoms) propose novel phase-separation paradigms, such as “hydrogen bubble/wisp” formation, challenging the classical “helium rain” scenario, striving to bridge atomic-scale dynamics to planetary-scale phase evolution.展开更多
Sub-surface crack networks in areas of altered microstructure are a common cause for bearing failures.Due to its appearance under light microscopy,the damage pattern is referred to as White Etching Cracks(WEC).The roo...Sub-surface crack networks in areas of altered microstructure are a common cause for bearing failures.Due to its appearance under light microscopy,the damage pattern is referred to as White Etching Cracks(WEC).The root causes leading to the formation of WEC are still under debate.Nevertheless,it has already been shown that atomic hydrogen can have an accelerating effect on the formation and propagation of WEC.In addition to hydrogen pre-charging,hydrogen can be released and absorbed during rolling/sliding due to the decomposing of the lubricant and water.The current work focuses on the analysis of the hydrogen content of cylindrical roller thrust bearings after testing in a FE8 type test rig using two different lubricants.Within the framework of this work,two different hydrogen analysis methods were used and assessed regarding their applicability.The results show that the so-called Hydrogen Collecting Analysis(HCA)is more suitable to investigate the correlation between lubricant chemistry and hydrogen content in the test bearings than the Local Hydrogen Analysis(LHA).The measurements with the HCA show a continuously increasing freely movable and diffusible hydrogen content under tribological conditions,which leads to the formation of WEC.Comparative tests with an oil without hydrogen showed that the tendency of the system to fail as a result of WEC can be reduced by using a lubricant without hydride compounds.展开更多
In this paper,the influence of microelements yttrium(Y)and tellurium(Te)on the diffusible hydrogen in weld bead has been investigated in a systemic way by means of alloying addition in the molten pool(AAMP).The result...In this paper,the influence of microelements yttrium(Y)and tellurium(Te)on the diffusible hydrogen in weld bead has been investigated in a systemic way by means of alloying addition in the molten pool(AAMP).The results indicate that AAMP can notably reduce the diffusible hydrogen,economize the precious microelements microelements and improve the technological properties.Thus the microelements will play an important role in further developing the welding materials.This paper lays emphasis on the discussion of the mechanism of reducing hydrogen by microelements Y and Te.It is considered from the results that both Y and Te belong to surface active elements and can reduce the diffusible hydrogen in weld bead because they can change the surface properlies of molten pool metal and reduce the absorption of hydrogen atom in arc space of liquid metal surface.This research has a great significance in the development and utilization of microelements in welding.展开更多
This study utilizes Direct FE^(2) multiscale simulation techniques to propose an innovative approach for analyzing hydrogen diffusion in Zircaloy cladding.This method combines finite element simulations at two scales ...This study utilizes Direct FE^(2) multiscale simulation techniques to propose an innovative approach for analyzing hydrogen diffusion in Zircaloy cladding.This method combines finite element simulations at two scales into a monolithic framework by utilizing downscaling rules and scaling factors.Through the investigation,it was found that voids induce non-uniform diffusion of lattice hydrogen,demonstrating a strong correlation between trapped concentration and microstructure.Additionally,the accumulation of trapped hydrogen leads to localized plastic deformation and a reduction in effective diffusivity.Furthermore,two representative volume elements were established to depict the void distribution at various stages of its evolution.It is evident that in the initial phases of void evolution,the hydrogen-induced softening effect facilitates crack propagation deep within the zirconium alloy cladding.Moreover,as void evolution progresses into the second stage,this effect intensifies the incidence of localized damage at the narrow inter-void ligaments.展开更多
Amorphous Ti2?xMgxNi (x=0?0.3) alloys were prepared by mechanical milling of elemental powders. Charge and discharge test, linear polarization (LP) and potential-step measurement were carried out to investigate the el...Amorphous Ti2?xMgxNi (x=0?0.3) alloys were prepared by mechanical milling of elemental powders. Charge and discharge test, linear polarization (LP) and potential-step measurement were carried out to investigate the electrochemical hydrogen storage properties of the alloys before and after heat treatment. The results show that the maximum discharge capacity of heat-treated Ti2?xMgxNi alloy can reach 275.3 mA·h/g, which is 100 mA·h/g higher than that of the amorphous Ti2?xMgxNi alloy. The heat-treated Ti1.9Mg0.1Ni alloy presents the best cycling stability with a high discharge capacity of 210 mA·h/g after 30 cycles. The results of LP and potential-step measurement of the Ti1.9Mg0.1Ni alloy show that the exchange current density increases from 101.1 to 203.3 mA/g and the hydrogen diffusion coefficient increases from 3.20×10?11 to 2.70×10?10 cm2/s after the heat treatment, indicating that the heat treatment facilitates both the charge-transfer and hydrogen diffusion processes, resulting in an improvement in electrochemical hydrogen storage properties of Ti2?xMgxNi (x=0?0.3) alloys.展开更多
The stress oriented hydrogen induced cracking (SOHIC) is a typical hydrogen embrittlement phenomenon occurring in the linepipe steels exposed to sour environment containing H 2 S gas.However,even recently,the cracking...The stress oriented hydrogen induced cracking (SOHIC) is a typical hydrogen embrittlement phenomenon occurring in the linepipe steels exposed to sour environment containing H 2 S gas.However,even recently,the cracking mechanism of SOHIC has not been clarified because of lacking in the empirical data on the actual failure mode of SOHIC cracking.The factors affecting SOHIC are discussed in terms of metallurgy of high strength linepipe steel and hydrogen electrochemistry.The cracking mechanisms of SOHIC are examined by comparing them with the empirical failure mode of SOHIC which is developed by observation of the actual fracture sites of the hydrogen induced blister cracking (HIBC) and secondary cracks.Finally,the correlation between SOHIC and HIC is discussed.展开更多
The effect of hydrogen on the fractttre behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing （SSRT） Hydrogen was introduced into the sample by electrochemical charging. The results sh...The effect of hydrogen on the fractttre behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing （SSRT） Hydrogen was introduced into the sample by electrochemical charging. The results show that surface microcracks form gradually during ag- ing at room temperature when desorption of hydrogen takes place after hydrogen charging at a current density of 5 mA/cm^2 for 24 h. SSRT shows that the increase of ductility loss is significantly obvious as the hydrogen charging current density increases. Scanning electron microscopy （SEM） images reveal ductile fracture in the pre-charged sample with low current densities, while the fracture includes small quasi-cleavage regions and tends to be brittle fracture as the hydrogen charging current density increases to 5 mA/cm^2.展开更多
In this paper, the microstructure and hardness of HG980D heat-affected zone （HAZ） at different cooling rate t8/3 were studied, the implant critical fracture stress under three diffusible hydrogen conditions were mea...In this paper, the microstructure and hardness of HG980D heat-affected zone （HAZ） at different cooling rate t8/3 were studied, the implant critical fracture stress under three diffusible hydrogen conditions were measured, and the hydrogeninduced cracking （H1C） fructograph of steel HG980D were analyzed, The experimental results show that martensite exists in HAZ of HG980D till ts/3 ≥ 150 s, the harden quenching tendency of HG980D is greater; The implant critical fracture stress is related to difJhsible hydrogen content significantly, at low hydrogen level, high restraint stress is needed to nucleate HIC, the fraetograph is mainly mierovoid coalescence, bat at high hydrogen level, only small restraint stress can cause H1C occurrence, the fractograph is mainly quasicleavage. It is very important to choose ultra-low hydrogen welding consumable to weld steel HG980D to prevent hydrogen-induced cracking.展开更多
Hydrogen dissolved in metals as a result of internal and external hydrogen can affect the mechanical properties of the metals, principally through the interactions between hydrogen and material defects. Multiple pheno...Hydrogen dissolved in metals as a result of internal and external hydrogen can affect the mechanical properties of the metals, principally through the interactions between hydrogen and material defects. Multiple phenomena such as hydrogen dissolution, hydrogen diffusion, hydrogen redistribution and hydrogen interactions with vacancies, dislocations, grain boundaries and other phase interfaces are involved in this process. Consequently, several hydrogen embrittlement(HE) mechanisms have been successively proposed to explain the HE phenomena, with the hydrogen-enhanced decohesion mechanism, hydrogenenhanced localized plasticity mechanism and hydrogen-enhanced strain-induced vacancies being some of the most important. Additionally, to reduce the risk of HE for engineering structural materials in service, surface treatments and microstructural optimization of the alloys have been suggested. In this review, we report on the progress of the studies on HE in metals, with a particular focus on steels. It focuses on four aspects:(1) hydrogen diffusion behavior;(2) hydrogen characterization methods;(3) HE mechanisms;and(4) the prevention of HE. The strengths and weaknesses of the current HE mechanisms and HE prevention methods are discussed, and specific research directions for further investigation of fundamental HE mechanisms and methods for preventing HE failure are identified.展开更多
This study investigated the susceptibility of X80 pipeline steel to hydrogen embrittlement given different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles in H2S environment.The fractur...This study investigated the susceptibility of X80 pipeline steel to hydrogen embrittlement given different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles in H2S environment.The fracture strain of the steel samples decreased with increasing hydrogen pre-charging time;this steel degradation could almost be recovered after diffusible hydrogen was removed when the hydrogen pre-charging time was<8 d.However,unrecoverable degeneration occurred when the hydrogen pre-charging time extended to 16–30 d.Moreover,nanovoid formation meant that the hydrogen damage to the steel under intermittent hydrogen pre-charging–releasing–recharging conditions was more serious than that under continuous hydrogen pre-charging conditions.This study illustrated that the mechanical degradation of steel is inevitable in an H2S environment even if diffusible hydrogen is removed or visible hydrogen-induced cracking is neglected.Furthermore,the steel samples showed premature fractures and exhibited a hydrogen fatigue effect because the repeated entry and release of diffusible hydrogen promoted the formation of vacancies that aggregated into nanovoids.Our results provide valuable information on the mechanical degradation of steel in an H2S environment,regarding the change rules of steel mechanical properties under different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles.展开更多
Density functional theory(DFT)calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg(0001)surface with Ni incorporating at various locations.The results show that Ni atom is pref...Density functional theory(DFT)calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg(0001)surface with Ni incorporating at various locations.The results show that Ni atom is preferentially located inside Mg matrix rather than in/over the topmost surface.Further calculations reveal that Ni atom locating in/over the topmost Mg(0001)surface exhibits excellent catalytic effect on hydrogen dissociation with an energy barrier of less than 0.05 eV.In these cases,the rate-limiting step has been converted from hydrogen dissociation to surface diffusion.In contrast,Ni doping inside Mg bulk not only does little help to hydrogen dissociation but also exhibits detrimental effect on hydrogen diffusion.Therefore,it is crucial to stabilize the Ni atom on the surface or in the topmost layer of Mg(0001)surface to maintain its catalytic effect.For all the case of Ni-incorporated Mg(0001)surfaces,the hydrogen atom prefers firstly immigrate along the surface and then penetrate into the bulk.It is expected that the theoretical findings in the present study could offer fundamental guidance to future designing on efficient Mg-based hydrogen storage materials.展开更多
Multi-principal element alloys exhibit excellent physical,chemical and mechanical properties,and they are used as novel structural materials for potential applications in nuclear energy,hydrogen energy,and petrochemic...Multi-principal element alloys exhibit excellent physical,chemical and mechanical properties,and they are used as novel structural materials for potential applications in nuclear energy,hydrogen energy,and petrochemical fields.However,exposing components made of the alloys to service conditions related to the mentioned applications may induce hydrogen embrittlement(HE)as one of the typical failure mechanisms.In this review,we report and summarize the progress in understanding HE in multi-principal element alloys,with a particular focus on high-entropy alloys(HEAs).The review focuses on four aspects:(1)hydrogen migration behavior(hydrogen dissolution,hydrogen diffusion,and hydrogen traps);(2)factors affecting HE(hydrogen concentration,alloy elements and microstructure);(3)tensile mechanical properties in the presence of hydrogen and micro-damage HE mechanisms;(4)the design concept for preventing hydrogen-induced mechanical degradation.The differences in the HE behavior and failure mechanisms between HEAs and traditional alloys are compared and discussed.Moreover,specific research directions for further investigation of fundamental HE issues and a strategy for a simultaneous improvement in strength and HE resistance are identified.展开更多
The hydrogen distribution of 16MnR steel weldment in hydrogen contained environment was calculated using the finite element method （ FEM）. The effect of welding residual stress on hydrogen diffusion has been discuss...The hydrogen distribution of 16MnR steel weldment in hydrogen contained environment was calculated using the finite element method （ FEM）. The effect of welding residual stress on hydrogen diffusion has been discussed using a 3-D sequential coupling finite element analysis procedure complied by Abaqus code. The hydrogen diffusion coefficient in weld metal, the heat affected zone （HAZ）, and the base metal of the 16MnR steel weldment were measured using the electrochemical permeation technique. The hydrogen diffusion without the effect of stress was also calculated and compared. Owing to the existence of welding residual stress, the hydrogen concentration was obviously increased and the hydrogen wouM diffuse and accumulate in the higher stress region.展开更多
The main impurities in aluminum melt are hydrogen and Al_2O_3,which can deteriorate melt quality and materials performance.However,the diffusion process of H atoms in aluminum melt and the interactions among Al atoms,...The main impurities in aluminum melt are hydrogen and Al_2O_3,which can deteriorate melt quality and materials performance.However,the diffusion process of H atoms in aluminum melt and the interactions among Al atoms,Al_2O_3 and hydrogen have been studied rarely.Molecular mechanics and dynamics simulations are employed to study the diffusion behaviors of different types of hydrogen,such as free H atoms,H atoms in H_2 and H^+ions in H_2O using COMPASS force field.Correspondingly,force field types h,h1h and h1o are used to describe different types of hydrogen which are labeled as H_h,H_(h1h) and H_(h1o).The results show that the adsorption areas are maximum for H_(h1o),followed by H_(h1h) and H_h.The diffusion ability of H_(h1o) is the strongest whereas H_h is hard to diffuse in aluminum melt because of the differences in radius and potential well depth of various types of hydrogen.Al_2O_3 cluster makes the Al atoms array disordered,creating the energy conditions for hydrogen diffusion in aluminum melt.Al_2O_3 improves the diffusion of H_h and H_(h1o),and constrains H_(h1h) which accumulates around it and forms gas porosities in aluminum.H_(h1o) is the most dispersive in aluminum melt,moreover,the distance of Al-H_(h1o) is shorter than that of Al-H_(h1h),both of which are detrimental to the removal of H_(h1o).The simulation results indicate that the gas porosities can be eliminated by the removal of Al_2O_3 inclusions,and the dispersive hydrogen can be removed by adsorption function of gas bubbles or molten fluxes.展开更多
A modelling suite for hydrogen transport during electrochemical permeation, degassing and thermal desorption spectroscopy is presented. The approach is based on Fick＇s diffusion laws, where the initial concentration ...A modelling suite for hydrogen transport during electrochemical permeation, degassing and thermal desorption spectroscopy is presented. The approach is based on Fick＇s diffusion laws, where the initial concentration and diffusion coefficients depend on microstructure and charging conditions. The evolution equations are shown to reduce to classical models for hydrogen diffusion and thermal desorption spectroscopy. The number density of trapping sites is found to be proportional to the mean spacing of each microstructural feature, including dislocations, grain boundaries and various precipitates. The model is validated with several steel grades and polycrystalline nickel for a wide range of processing conditions and microstructures. A systematic study of the factors affecting hydrogen mobility in martensitic steels showed that dislocations control the effective diffusion coefficient of hydrogen. However,they also release hydrogen into the lattice more rapidly than other kind of traps. It is suggested that these effects contribute to the increased susceptibility to hydrogen embrittlement in martensitic and other high-strength steels. These results show that the methodology can be employed as a tool for alloy and process design, and that dislocation kinematics play a crucial role in such design.展开更多
The principle, design, construction and performance of the amperometric and potentiometric sensors for measuring the permeation rate of hydrogen through the wall of metal equipment were investigated in order to develo...The principle, design, construction and performance of the amperometric and potentiometric sensors for measuring the permeation rate of hydrogen through the wall of metal equipment were investigated in order to develop a new type of hydrogen sensor with high accuracy. The transient curves of hydrogen permeation under a given charging condition were employed to evaluate the performance of two types of hydrogen sensors. The relative deviation of the hydrogen concentration detected with two types of sensors under the same condition varied from 3.0% to 13%. The accuracy, response time, reproducibility, and installation were discussed and compared. Response time of the potentiometric sensor （E-sensor） was shorter than that of the amperometric sensor （I-sensor）. Both types of sensors exhibited good reproducibility. Development of I-sensor composed of a kind of proton conductor adhesives or non-fluid electrolytes which contain two functions of high electrical conductivity and a strong adhesion will be a promising prospect in order to measure hydrogen permeation at high temperature.展开更多
High strength bolt steel 0Crl6Ni5Mo was charged with hydrogen by means of electrochemical technique to evaluate the hydrogen diffusion behavior. The bolt steels were investigated by a combination of electrochemical hy...High strength bolt steel 0Crl6Ni5Mo was charged with hydrogen by means of electrochemical technique to evaluate the hydrogen diffusion behavior. The bolt steels were investigated by a combination of electrochemical hydrogen permeation, thermal desorption spectroscopy （TDS）, slow strain rate test （SSRT） and microstructure observation. The hydrogen concentration of both 10.9 grade （Rm=950-1 150 MPa） and 12.9 grade （Rm=1 150-1 250 MPa） bolt steels increases with increasing the hydrogen charging current densities and charging time. The 12.9 grade bolt steel has higher apparent diffusion coefficient than 10.9 grade steel, corresponding to the value of 4.7×10 7 mm^2/s. By means of TDS tests, the activation energies of the two experimental steels are 17.74 kJ/mol and 18.92 kJ/mol, respectively. The hydrogen traps of both grade bolt steels are dislocations and crystal lattice. The notch tensile strength of the steels is reduced with the hydrogen concentration carried out by SSRT. The fracture morphologies of the steels after hydrogen charging present ductile dimple and quasi-cleavage characteristic.展开更多
The influence of temperature on the hydrogen diffusion behavior in X80 pipeline steel during stacking for slow cooling was studied using electrochemical penetration method, the temperature field and the hydrogen diffu...The influence of temperature on the hydrogen diffusion behavior in X80 pipeline steel during stacking for slow cooling was studied using electrochemical penetration method, the temperature field and the hydrogen diffusion in this pipeline steel during stacking for slow cooling were simulated by ABAQUS finite element method （FEM） software. The results show that in this process there is a reciprocal relationship between the natural logarithm of hydrogen diffusion coefficient and temperature. The cooling rate decreases gradually with the increase of steel plate thickness. The hydrogen content is higher at high temperature （500-400 ℃） than that in low temperature region （300-100 ℃）. The FEM simulation results are consistent with the experimental ones, and the model can be used to predict the hydrogen diffusion behavior in industrial production of X80 pipeline steel.展开更多
Permeability and diffusivity of hydrogen in Fe-Ni-Co based superalloy lncoloy 903 were measured over the temperature range of 220 to 420℃ using a gaseous permeation technique. The effect of strengthening phase γ'...Permeability and diffusivity of hydrogen in Fe-Ni-Co based superalloy lncoloy 903 were measured over the temperature range of 220 to 420℃ using a gaseous permeation technique. The effect of strengthening phase γ' precipitated after being aged on the hydrogen permeation and diffusion was investigated.It was indicated that the permeability and diffusivity of hydrogen in the alloy hardly depend on heat treatment condition and are not af- fected by γ' phase precipitated after being aged.The relationships between the permeability and diffusivity of hydrogen and the temperature can be respectively expressed as Φ=9.36×10^(-5)exp[-54.20(kJ/mol)/RT]mol/m·s·MPa^(1/2)and D=4.24×10^(-7)exp[-49.07(kJ/mol)/RT]m^2/s.展开更多
基金supported by the Korea Institute for Advance-ment of Technology(KIAT)grant funded by the Korea Government(MOTIE)(HRD Program for Industrial Innovation)(No.P0023676)the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(Nos.NRF-2022R1A5A1030054 and RS-2023-00281508).
文摘Medium-entropy alloys(MEAs)that exhibit transformation-induced plasticity(TRIP)from face-centered cubic(FCC)to body-centered cubic(BCC)are considered promising for liquid hydrogen environments due to their remarkable cryogenic strength.Nonetheless,studies on hydrogen embrittlement(HE)in BCC-TRIP MEAs have not been conducted,although the TRIP effect and consequent BCC martensite usually deteriorate HE susceptibility.In these alloys,initial as-quenched martensite alters hydrogen diffusion and trap behavior,and deformation-induced martensitic transformation(DIMT)provides preferred crack propagation sites,which critically affects HE susceptibility.Therefore,this study aims to investigate the HE behav-ior of BCC-TRIP MEAs by designing four V10 Cr_(10)Co_(30)Fe_(50-x)Ni_(x)(x=0,1,2,and 3 at%)MEAs,adjusting both the initial phase constituent and phase metastability.A decreased Ni content leads to a reduced fraction and mechanical stability of FCC,which in turn increases HE susceptibility,as determined through electro-chemical hydrogen pre-charging and slow-strain rate tests The permeation test and thermal desorption analysis reveal that the hydrogen diffusivity and content are affected by initial BCC fraction,interconnectivity of BCC,and refined FCC.As these initial phase constituents differ between the alloys with FCC-and BCC-dominant initial phase,microstructural factors affecting HE are unveiled discretely among these alloy groups by correlation of hydrogen-induced crack behavior with hydrogen diffusion and trap behavior.In alloys with an FCC-dominant initial phase,the initial BCC fraction and DIMT initiation rate emerge as critical factors,rather than the extent of DIMT.For BCC-dominant alloys,the primary contributor is an increase in the initial BCC fraction,rather than the extent or rate of DIMT.The unraveled roles of microstructural factors provide insights into designing HE-resistant BCC-TRIP MEAs.
基金supported by the National University of Defense Technology Research Fund Projectthe National Natural Science Foundation of China under Grant Nos. 12047561 and 12104507+1 种基金the NSAF under Grant No. U1830206the Science and Technology Innovation Program of Hunan Province under Grant No. 2021RC4026。
文摘The dynamics of phase separation in H–He binary systems within gas giants such as Jupiter and Saturn exhibit remarkable complexity, yet lack systematic investigation. Through large-scale machine-learning-accelerated molecular dynamics simulations spanning broad temperature-pressure-composition(2000–10000 K, 1–7 Mbar,pure H to pure He) regimes, we systematically determine self and mutual diffusion coefficients in H–He systems and establish a six-dimensional framework correlating temperature, pressure, helium abundance, phase separation degree, diffusion coefficients, and anisotropy. Key findings reveal that hydrogen exhibits active directional migration with pronounced diffusion anisotropy, whereas helium passively aggregates in response. While the conventional mixing rule underestimates mutual diffusion coefficients by neglecting velocity cross-correlations,the assumption of an ideal thermodynamic factor(Q = 1) overestimates them due to unaccounted non-ideal thermodynamic effects—both particularly pronounced in strongly phase-separated regimes. Notably, hydrogen's dual role, anisotropic diffusion and bond stabilization via helium doping, modulates demixing kinetics. Large-scale simulations(216,000 atoms) propose novel phase-separation paradigms, such as “hydrogen bubble/wisp” formation, challenging the classical “helium rain” scenario, striving to bridge atomic-scale dynamics to planetary-scale phase evolution.
基金The authors would like to thank the ResearchAssociation for Drive Technology (FVA) for thefunding and support from the research work throughthe research project FVA 707 IV
文摘Sub-surface crack networks in areas of altered microstructure are a common cause for bearing failures.Due to its appearance under light microscopy,the damage pattern is referred to as White Etching Cracks(WEC).The root causes leading to the formation of WEC are still under debate.Nevertheless,it has already been shown that atomic hydrogen can have an accelerating effect on the formation and propagation of WEC.In addition to hydrogen pre-charging,hydrogen can be released and absorbed during rolling/sliding due to the decomposing of the lubricant and water.The current work focuses on the analysis of the hydrogen content of cylindrical roller thrust bearings after testing in a FE8 type test rig using two different lubricants.Within the framework of this work,two different hydrogen analysis methods were used and assessed regarding their applicability.The results show that the so-called Hydrogen Collecting Analysis(HCA)is more suitable to investigate the correlation between lubricant chemistry and hydrogen content in the test bearings than the Local Hydrogen Analysis(LHA).The measurements with the HCA show a continuously increasing freely movable and diffusible hydrogen content under tribological conditions,which leads to the formation of WEC.Comparative tests with an oil without hydrogen showed that the tendency of the system to fail as a result of WEC can be reduced by using a lubricant without hydride compounds.
文摘In this paper,the influence of microelements yttrium(Y)and tellurium(Te)on the diffusible hydrogen in weld bead has been investigated in a systemic way by means of alloying addition in the molten pool(AAMP).The results indicate that AAMP can notably reduce the diffusible hydrogen,economize the precious microelements microelements and improve the technological properties.Thus the microelements will play an important role in further developing the welding materials.This paper lays emphasis on the discussion of the mechanism of reducing hydrogen by microelements Y and Te.It is considered from the results that both Y and Te belong to surface active elements and can reduce the diffusible hydrogen in weld bead because they can change the surface properlies of molten pool metal and reduce the absorption of hydrogen atom in arc space of liquid metal surface.This research has a great significance in the development and utilization of microelements in welding.
基金supported by the National Natural Science Foundation of China(Grant No.52301131)Natural Science Foundation of Sichuan,China(Grant No.2023NSFSC0908)Research Foundation for Talents of Chengdu Technological University(Grant No.2023RC017).
文摘This study utilizes Direct FE^(2) multiscale simulation techniques to propose an innovative approach for analyzing hydrogen diffusion in Zircaloy cladding.This method combines finite element simulations at two scales into a monolithic framework by utilizing downscaling rules and scaling factors.Through the investigation,it was found that voids induce non-uniform diffusion of lattice hydrogen,demonstrating a strong correlation between trapped concentration and microstructure.Additionally,the accumulation of trapped hydrogen leads to localized plastic deformation and a reduction in effective diffusivity.Furthermore,two representative volume elements were established to depict the void distribution at various stages of its evolution.It is evident that in the initial phases of void evolution,the hydrogen-induced softening effect facilitates crack propagation deep within the zirconium alloy cladding.Moreover,as void evolution progresses into the second stage,this effect intensifies the incidence of localized damage at the narrow inter-void ligaments.
基金Project(51201089)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions of China
文摘Amorphous Ti2?xMgxNi (x=0?0.3) alloys were prepared by mechanical milling of elemental powders. Charge and discharge test, linear polarization (LP) and potential-step measurement were carried out to investigate the electrochemical hydrogen storage properties of the alloys before and after heat treatment. The results show that the maximum discharge capacity of heat-treated Ti2?xMgxNi alloy can reach 275.3 mA·h/g, which is 100 mA·h/g higher than that of the amorphous Ti2?xMgxNi alloy. The heat-treated Ti1.9Mg0.1Ni alloy presents the best cycling stability with a high discharge capacity of 210 mA·h/g after 30 cycles. The results of LP and potential-step measurement of the Ti1.9Mg0.1Ni alloy show that the exchange current density increases from 101.1 to 203.3 mA/g and the hydrogen diffusion coefficient increases from 3.20×10?11 to 2.70×10?10 cm2/s after the heat treatment, indicating that the heat treatment facilitates both the charge-transfer and hydrogen diffusion processes, resulting in an improvement in electrochemical hydrogen storage properties of Ti2?xMgxNi (x=0?0.3) alloys.
文摘The stress oriented hydrogen induced cracking (SOHIC) is a typical hydrogen embrittlement phenomenon occurring in the linepipe steels exposed to sour environment containing H 2 S gas.However,even recently,the cracking mechanism of SOHIC has not been clarified because of lacking in the empirical data on the actual failure mode of SOHIC cracking.The factors affecting SOHIC are discussed in terms of metallurgy of high strength linepipe steel and hydrogen electrochemistry.The cracking mechanisms of SOHIC are examined by comparing them with the empirical failure mode of SOHIC which is developed by observation of the actual fracture sites of the hydrogen induced blister cracking (HIBC) and secondary cracks.Finally,the correlation between SOHIC and HIC is discussed.
文摘The effect of hydrogen on the fractttre behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing （SSRT） Hydrogen was introduced into the sample by electrochemical charging. The results show that surface microcracks form gradually during ag- ing at room temperature when desorption of hydrogen takes place after hydrogen charging at a current density of 5 mA/cm^2 for 24 h. SSRT shows that the increase of ductility loss is significantly obvious as the hydrogen charging current density increases. Scanning electron microscopy （SEM） images reveal ductile fracture in the pre-charged sample with low current densities, while the fracture includes small quasi-cleavage regions and tends to be brittle fracture as the hydrogen charging current density increases to 5 mA/cm^2.
文摘In this paper, the microstructure and hardness of HG980D heat-affected zone （HAZ） at different cooling rate t8/3 were studied, the implant critical fracture stress under three diffusible hydrogen conditions were measured, and the hydrogeninduced cracking （H1C） fructograph of steel HG980D were analyzed, The experimental results show that martensite exists in HAZ of HG980D till ts/3 ≥ 150 s, the harden quenching tendency of HG980D is greater; The implant critical fracture stress is related to difJhsible hydrogen content significantly, at low hydrogen level, high restraint stress is needed to nucleate HIC, the fraetograph is mainly mierovoid coalescence, bat at high hydrogen level, only small restraint stress can cause H1C occurrence, the fractograph is mainly quasicleavage. It is very important to choose ultra-low hydrogen welding consumable to weld steel HG980D to prevent hydrogen-induced cracking.
基金the National Natural Science Foundation of China(No.51505477)the Guangdong Provincial Key S&T Special Project(Nos.2017B020235001 and 20198010943001)+1 种基金the Guangdong Education Department Fund(No.2016KQNCX005)basic start-up fund of Sun-Yat Sen University(45000-18841218)。
文摘Hydrogen dissolved in metals as a result of internal and external hydrogen can affect the mechanical properties of the metals, principally through the interactions between hydrogen and material defects. Multiple phenomena such as hydrogen dissolution, hydrogen diffusion, hydrogen redistribution and hydrogen interactions with vacancies, dislocations, grain boundaries and other phase interfaces are involved in this process. Consequently, several hydrogen embrittlement(HE) mechanisms have been successively proposed to explain the HE phenomena, with the hydrogen-enhanced decohesion mechanism, hydrogenenhanced localized plasticity mechanism and hydrogen-enhanced strain-induced vacancies being some of the most important. Additionally, to reduce the risk of HE for engineering structural materials in service, surface treatments and microstructural optimization of the alloys have been suggested. In this review, we report on the progress of the studies on HE in metals, with a particular focus on steels. It focuses on four aspects:(1) hydrogen diffusion behavior;(2) hydrogen characterization methods;(3) HE mechanisms;and(4) the prevention of HE. The strengths and weaknesses of the current HE mechanisms and HE prevention methods are discussed, and specific research directions for further investigation of fundamental HE mechanisms and methods for preventing HE failure are identified.
基金financially supported by the National Natural Science Foundation of China (Nos. 51805292, 51671215, and 51425502)the National Postdoctoral Program for Innovative Talents of China (No. BX201700132)
文摘This study investigated the susceptibility of X80 pipeline steel to hydrogen embrittlement given different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles in H2S environment.The fracture strain of the steel samples decreased with increasing hydrogen pre-charging time;this steel degradation could almost be recovered after diffusible hydrogen was removed when the hydrogen pre-charging time was<8 d.However,unrecoverable degeneration occurred when the hydrogen pre-charging time extended to 16–30 d.Moreover,nanovoid formation meant that the hydrogen damage to the steel under intermittent hydrogen pre-charging–releasing–recharging conditions was more serious than that under continuous hydrogen pre-charging conditions.This study illustrated that the mechanical degradation of steel is inevitable in an H2S environment even if diffusible hydrogen is removed or visible hydrogen-induced cracking is neglected.Furthermore,the steel samples showed premature fractures and exhibited a hydrogen fatigue effect because the repeated entry and release of diffusible hydrogen promoted the formation of vacancies that aggregated into nanovoids.Our results provide valuable information on the mechanical degradation of steel in an H2S environment,regarding the change rules of steel mechanical properties under different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles.
基金the financial support from the National Natural Science Foundation of China(Grant Nos.U1610103,21805169 and 21978156)Shandong Provincial Natural Science Foundation,China(Grant No.ZR2018BB069)Project of Shandong Province Higher Educational Young Innovative Talent Introduction and Cultivation Team(Hydrogen energy chemistry innovation team)。
文摘Density functional theory(DFT)calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg(0001)surface with Ni incorporating at various locations.The results show that Ni atom is preferentially located inside Mg matrix rather than in/over the topmost surface.Further calculations reveal that Ni atom locating in/over the topmost Mg(0001)surface exhibits excellent catalytic effect on hydrogen dissociation with an energy barrier of less than 0.05 eV.In these cases,the rate-limiting step has been converted from hydrogen dissociation to surface diffusion.In contrast,Ni doping inside Mg bulk not only does little help to hydrogen dissociation but also exhibits detrimental effect on hydrogen diffusion.Therefore,it is crucial to stabilize the Ni atom on the surface or in the topmost layer of Mg(0001)surface to maintain its catalytic effect.For all the case of Ni-incorporated Mg(0001)surfaces,the hydrogen atom prefers firstly immigrate along the surface and then penetrate into the bulk.It is expected that the theoretical findings in the present study could offer fundamental guidance to future designing on efficient Mg-based hydrogen storage materials.
基金supported by the National Natural Science Foundation of China(No.12104057)the Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110895)+5 种基金the State Key Laboratory for Mechanical Behavior of Materials(No.20202209)the State Key Laboratory of Advanced Metals and Materials(No.2021-Z02)the Open Project of State Key Laboratory of Advanced Special SteelShanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS 2021-08)the Science and Technology Commission of Shanghai Municipality(Nos.19DZ2270200 and 20511107700)the Major Engineering Materials Service Safety Research Evaluation Facility National Major Science and Technology Infrastructure Open Project Fund。
文摘Multi-principal element alloys exhibit excellent physical,chemical and mechanical properties,and they are used as novel structural materials for potential applications in nuclear energy,hydrogen energy,and petrochemical fields.However,exposing components made of the alloys to service conditions related to the mentioned applications may induce hydrogen embrittlement(HE)as one of the typical failure mechanisms.In this review,we report and summarize the progress in understanding HE in multi-principal element alloys,with a particular focus on high-entropy alloys(HEAs).The review focuses on four aspects:(1)hydrogen migration behavior(hydrogen dissolution,hydrogen diffusion,and hydrogen traps);(2)factors affecting HE(hydrogen concentration,alloy elements and microstructure);(3)tensile mechanical properties in the presence of hydrogen and micro-damage HE mechanisms;(4)the design concept for preventing hydrogen-induced mechanical degradation.The differences in the HE behavior and failure mechanisms between HEAs and traditional alloys are compared and discussed.Moreover,specific research directions for further investigation of fundamental HE issues and a strategy for a simultaneous improvement in strength and HE resistance are identified.
文摘The hydrogen distribution of 16MnR steel weldment in hydrogen contained environment was calculated using the finite element method （ FEM）. The effect of welding residual stress on hydrogen diffusion has been discussed using a 3-D sequential coupling finite element analysis procedure complied by Abaqus code. The hydrogen diffusion coefficient in weld metal, the heat affected zone （HAZ）, and the base metal of the 16MnR steel weldment were measured using the electrochemical permeation technique. The hydrogen diffusion without the effect of stress was also calculated and compared. Owing to the existence of welding residual stress, the hydrogen concentration was obviously increased and the hydrogen wouM diffuse and accumulate in the higher stress region.
基金financially supported by the International Cooperation Project of Science and Technology Ministry of China(No.2015DFA71350)Important Science and Technology Programs of Fujian province(No.2012H0006)
文摘The main impurities in aluminum melt are hydrogen and Al_2O_3,which can deteriorate melt quality and materials performance.However,the diffusion process of H atoms in aluminum melt and the interactions among Al atoms,Al_2O_3 and hydrogen have been studied rarely.Molecular mechanics and dynamics simulations are employed to study the diffusion behaviors of different types of hydrogen,such as free H atoms,H atoms in H_2 and H^+ions in H_2O using COMPASS force field.Correspondingly,force field types h,h1h and h1o are used to describe different types of hydrogen which are labeled as H_h,H_(h1h) and H_(h1o).The results show that the adsorption areas are maximum for H_(h1o),followed by H_(h1h) and H_h.The diffusion ability of H_(h1o) is the strongest whereas H_h is hard to diffuse in aluminum melt because of the differences in radius and potential well depth of various types of hydrogen.Al_2O_3 cluster makes the Al atoms array disordered,creating the energy conditions for hydrogen diffusion in aluminum melt.Al_2O_3 improves the diffusion of H_h and H_(h1o),and constrains H_(h1h) which accumulates around it and forms gas porosities in aluminum.H_(h1o) is the most dispersive in aluminum melt,moreover,the distance of Al-H_(h1o) is shorter than that of Al-H_(h1h),both of which are detrimental to the removal of H_(h1o).The simulation results indicate that the gas porosities can be eliminated by the removal of Al_2O_3 inclusions,and the dispersive hydrogen can be removed by adsorption function of gas bubbles or molten fluxes.
文摘A modelling suite for hydrogen transport during electrochemical permeation, degassing and thermal desorption spectroscopy is presented. The approach is based on Fick＇s diffusion laws, where the initial concentration and diffusion coefficients depend on microstructure and charging conditions. The evolution equations are shown to reduce to classical models for hydrogen diffusion and thermal desorption spectroscopy. The number density of trapping sites is found to be proportional to the mean spacing of each microstructural feature, including dislocations, grain boundaries and various precipitates. The model is validated with several steel grades and polycrystalline nickel for a wide range of processing conditions and microstructures. A systematic study of the factors affecting hydrogen mobility in martensitic steels showed that dislocations control the effective diffusion coefficient of hydrogen. However,they also release hydrogen into the lattice more rapidly than other kind of traps. It is suggested that these effects contribute to the increased susceptibility to hydrogen embrittlement in martensitic and other high-strength steels. These results show that the methodology can be employed as a tool for alloy and process design, and that dislocation kinematics play a crucial role in such design.
基金supported by National Natural Science Foundation of China (No.21176061)China and Science and Technology Planning Project (2013FJ3023) of Hunan Province in China
文摘The principle, design, construction and performance of the amperometric and potentiometric sensors for measuring the permeation rate of hydrogen through the wall of metal equipment were investigated in order to develop a new type of hydrogen sensor with high accuracy. The transient curves of hydrogen permeation under a given charging condition were employed to evaluate the performance of two types of hydrogen sensors. The relative deviation of the hydrogen concentration detected with two types of sensors under the same condition varied from 3.0% to 13%. The accuracy, response time, reproducibility, and installation were discussed and compared. Response time of the potentiometric sensor （E-sensor） was shorter than that of the amperometric sensor （I-sensor）. Both types of sensors exhibited good reproducibility. Development of I-sensor composed of a kind of proton conductor adhesives or non-fluid electrolytes which contain two functions of high electrical conductivity and a strong adhesion will be a promising prospect in order to measure hydrogen permeation at high temperature.
基金the funding of this work by Luoyang Sunrui Special Equipment Co.,Ltd.in Luoyang(China)
文摘High strength bolt steel 0Crl6Ni5Mo was charged with hydrogen by means of electrochemical technique to evaluate the hydrogen diffusion behavior. The bolt steels were investigated by a combination of electrochemical hydrogen permeation, thermal desorption spectroscopy （TDS）, slow strain rate test （SSRT） and microstructure observation. The hydrogen concentration of both 10.9 grade （Rm=950-1 150 MPa） and 12.9 grade （Rm=1 150-1 250 MPa） bolt steels increases with increasing the hydrogen charging current densities and charging time. The 12.9 grade bolt steel has higher apparent diffusion coefficient than 10.9 grade steel, corresponding to the value of 4.7×10 7 mm^2/s. By means of TDS tests, the activation energies of the two experimental steels are 17.74 kJ/mol and 18.92 kJ/mol, respectively. The hydrogen traps of both grade bolt steels are dislocations and crystal lattice. The notch tensile strength of the steels is reduced with the hydrogen concentration carried out by SSRT. The fracture morphologies of the steels after hydrogen charging present ductile dimple and quasi-cleavage characteristic.
文摘The influence of temperature on the hydrogen diffusion behavior in X80 pipeline steel during stacking for slow cooling was studied using electrochemical penetration method, the temperature field and the hydrogen diffusion in this pipeline steel during stacking for slow cooling were simulated by ABAQUS finite element method （FEM） software. The results show that in this process there is a reciprocal relationship between the natural logarithm of hydrogen diffusion coefficient and temperature. The cooling rate decreases gradually with the increase of steel plate thickness. The hydrogen content is higher at high temperature （500-400 ℃） than that in low temperature region （300-100 ℃）. The FEM simulation results are consistent with the experimental ones, and the model can be used to predict the hydrogen diffusion behavior in industrial production of X80 pipeline steel.
文摘Permeability and diffusivity of hydrogen in Fe-Ni-Co based superalloy lncoloy 903 were measured over the temperature range of 220 to 420℃ using a gaseous permeation technique. The effect of strengthening phase γ' precipitated after being aged on the hydrogen permeation and diffusion was investigated.It was indicated that the permeability and diffusivity of hydrogen in the alloy hardly depend on heat treatment condition and are not af- fected by γ' phase precipitated after being aged.The relationships between the permeability and diffusivity of hydrogen and the temperature can be respectively expressed as Φ=9.36×10^(-5)exp[-54.20(kJ/mol)/RT]mol/m·s·MPa^(1/2)and D=4.24×10^(-7)exp[-49.07(kJ/mol)/RT]m^2/s.
