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
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
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
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
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
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
Hydrogen diffusion coefficients of different regions in the welded joint of X80 pipeline steel were measured using the electro-chemical permeation technique. Using ABAQUS software, hydrogen diffusion in X80 pipeline s...Hydrogen diffusion coefficients of different regions in the welded joint of X80 pipeline steel were measured using the electro-chemical permeation technique. Using ABAQUS software, hydrogen diffusion in X80 pipeline steel welded joint was studied in consideration of the inhomogeneity of the welding zone, and temperature-dependent thermo-physical and mechanical properties of the metals. A three dimensional finite element model was developed and a coupled thermo-mechanical-diffusion analysis was performed. Hydrogen concentration distribution across the welded joint was obtained. It is found that the postweld residual hydrogen exhibits a non-uniform distribution across the welded joint. A maximum equivalent stress occurs in the immediate vicinity of the weld metal. The heat affected zone has the highest hydrogen concentration level, followed by the weld zone and the base metal.Simulation results are well consistent with theoretical analysis.展开更多
The formation condition of hydrogen blister in 18Ni maraging steel without any inner or external stress was investigated. The results show that the critical diffusible hydrogen concentration of a blister forming is ab...The formation condition of hydrogen blister in 18Ni maraging steel without any inner or external stress was investigated. The results show that the critical diffusible hydrogen concentration of a blister forming is about 1.4×10^-5 , which is corresponding to the current density of 30 mA/cm^2 during cathodic charging in a sodium hydroxide solution. For a 0.1 cm thick sample, no matter the current density is equal to or much larger than the critical value, it spends at least about 132 h to form a hydrogen blister when hydrogen charging in single direction. It is approxi- mately equal to the time for hydrogen atom to diffuse throughout the sample, which exactly depends on the hydrogen diffusion coefficient and the penetration depth. The very first clear suggestion was reported that the incubation period for hydrogen blister nucleation was necessary. According to the Fick＇s laws, calculations show that the normalized hydrogen concentration in the escaping surface almost reaches 0.96 times of the charging surface, which means that the diffusion almost reaches a dynamic balance. A model was illustrated to describe the competitive relationship between hydrogen diffusion and blister formation.展开更多
The model of hydrogen diffusion formerly de- veloped [1] has been applied successfully to the hydrogen permeation experiment results of three kinds of materials,α—Fe,Fe—Ti alloy and Fe—Ti—C alloy by the mathemati...The model of hydrogen diffusion formerly de- veloped [1] has been applied successfully to the hydrogen permeation experiment results of three kinds of materials,α—Fe,Fe—Ti alloy and Fe—Ti—C alloy by the mathematical fitting method.From the fitting results it was shown that the model can re- fiect well the diffusion of hydrogen in the materials with trapping.The obtained trapping parameters(α and β)can be used to explain well the diffusion of hydrogen in the samples with trapping.展开更多
The influence of alloy composition (Ti, Mn, TiN) on hydrogen diffusion in Fe was studied in detail using SCM-DV-Xα method. The voltage barriers were obtained via calculation on Fe clusters containing the alloy elemen...The influence of alloy composition (Ti, Mn, TiN) on hydrogen diffusion in Fe was studied in detail using SCM-DV-Xα method. The voltage barriers were obtained via calculation on Fe clusters containing the alloy elements such as Ti, Mn as well as the chemical compound TiN respectively. The results showed that Ti element produced deep trap in Fe, decreasing the diffusion coefficient of hydrogen elements, Mn element did not produce deep trap in Fe, decreasing the diffusion coefficient slightly and TiN in Fe produced very deep "trap" decreasing the diffusion coefficient obviously. The calculation results were in agreement with experiment results.展开更多
Hydrogen diffusion coefficients in amorphous Ti0.88Ni1.00 film were measured using electrochemical permeation technique. Diffusion coefficients increased with increasing hydrogen concentration. Activation energy of hy...Hydrogen diffusion coefficients in amorphous Ti0.88Ni1.00 film were measured using electrochemical permeation technique. Diffusion coefficients increased with increasing hydrogen concentration. Activation energy of hydrogen diffusion was determined through measurement of the steady state anodic diffusion current density as a function of temperature, and an equation was derived to calculate the activation energy.展开更多
A new model of hydrogen diffusion in metals has been developed,it is more efficient to describe the hydrogen diffusion with trapping in metals.In the model newly developed an impli- cit dependence on time of hydrogen ...A new model of hydrogen diffusion in metals has been developed,it is more efficient to describe the hydrogen diffusion with trapping in metals.In the model newly developed an impli- cit dependence on time of hydrogen diffusion coefficient in metals with trapping was firstly built and it is shown that hydrogen diffusion coefficient will be different at different posi- tions in a dynamic process of hydrogen diffusion in a metal. Numerical solutions of the present model were obtained by finite difference method.By changing the parameters in the model the diffusion of hydrogen in a metal and the effect of trapping were described and discussed.And the comparison between the well known McNabb and Foster's model and the present model was also made.展开更多
The Proccss of gascous hydrogcn charging into a Ti_3Al- based alloy in the temperature range of 500-650℃isinvcstigatcd. The rcsnlls snoxvc that in rclatiollshil, between the average hydrogen concentration at constant...The Proccss of gascous hydrogcn charging into a Ti_3Al- based alloy in the temperature range of 500-650℃isinvcstigatcd. The rcsnlls snoxvc that in rclatiollshil, between the average hydrogen concentration at constant tempreature and charging time reveals a parabolie rate law Applying the theory of lattice constant tcnlpcralurc and hrgillg tin rcvcals a parabolic riltc laiv. Applyillg tbcthcoly oftatticc dillbsio to allalyzc the hydrogcll diethesioll they andthat cncrgy of hydrogcn diffusion is 90.40 kJ/mol. and the equilibrium hydrogen content in the alloy depends on the temperature of the gaseous hydrogen charging process展开更多
Hydrogen diffusion coefficients in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 alloy electrode as a function of state of charge (SOC) or temperature were determined by chronoamperometry. It is found that hydrogen diffusion coeffi...Hydrogen diffusion coefficients in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 alloy electrode as a function of state of charge (SOC) or temperature were determined by chronoamperometry. It is found that hydrogen diffusion coefficient decreases with the increase of SOC or the decrease of temperature. The activation energy for hydrogen diffusion in the alloy electrode with 50%SOC is evaluated to be 19.9?kJ/mol.展开更多
Absorption and desorption processes of hydrogen in metals are facilitated by alloying elements;however,the formation of secondary phases often reduces storage capacity.The alloying effect on the hydrogen kinetics has ...Absorption and desorption processes of hydrogen in metals are facilitated by alloying elements;however,the formation of secondary phases often reduces storage capacity.The alloying effect on the hydrogen kinetics has been examined by time-lag permeation measurement,which lacks spatial resolution and yields the averaged diffusion coefficient from multiple phases.Here,we report an advanced scanning Kelvin probe force microscopy,combined with in-situ hydrogen loading system for submicron-scale measurement of diffusion kinetics in metals.Successive probing of the surface during hydrogen loading detects the temporal and spatial variations in the surface potential,enabling the estimation of diffusion coefficient.Not only for a single-phase magnesium but also for multiphase titaniumiron based alloys,we can obtain the diffusion coefficients of hydrogen in each phase.The estimated diffusion coefficients for TiFe alloys are higher than that for the pristine TiFe intermetallic compound,due to alloying elements that reduce the diffusion barrier and modify bond character.Our approach paves the way to the microscopic understanding of hydrogen diffusion in metals.展开更多
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
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
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
In the present work. the hydrogen permeation and diffusion in two low-carbon steels. # 10 and #20. and 16Mn stee1 over the temperature range of 80 to 330℃ were investigated using gaseous permeation technique. The tem...In the present work. the hydrogen permeation and diffusion in two low-carbon steels. # 10 and #20. and 16Mn stee1 over the temperature range of 80 to 330℃ were investigated using gaseous permeation technique. The temperature dependence of hydrogen permeability. diffusivity and solubility for the three steels was obtained in the form of the Arrhenius equations. It was shown that the hydrogen permeability of the 16Mn steel is somewhat lower than that of the two low-carbon steels.whereas the hydrogen diffusivity is lowered in the order of #10, #20 and 16Mn but the activation energy of diffusion is much the same for the three steels. The difference in the diffusivity was attributed to the increase of ferrite-cementite interface areas with the refinement of pearlitic structure in the steels展开更多
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 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.
基金Project(BK2011258)supported by the Natural Science Foundation of Jiangsu Province,China
文摘Hydrogen diffusion coefficients of different regions in the welded joint of X80 pipeline steel were measured using the electro-chemical permeation technique. Using ABAQUS software, hydrogen diffusion in X80 pipeline steel welded joint was studied in consideration of the inhomogeneity of the welding zone, and temperature-dependent thermo-physical and mechanical properties of the metals. A three dimensional finite element model was developed and a coupled thermo-mechanical-diffusion analysis was performed. Hydrogen concentration distribution across the welded joint was obtained. It is found that the postweld residual hydrogen exhibits a non-uniform distribution across the welded joint. A maximum equivalent stress occurs in the immediate vicinity of the weld metal. The heat affected zone has the highest hydrogen concentration level, followed by the weld zone and the base metal.Simulation results are well consistent with theoretical analysis.
基金Item Sponsored by National Natural Science Foundation of China(51571029,51071025)National Basic Research Program of China(2014CB643301)
文摘The formation condition of hydrogen blister in 18Ni maraging steel without any inner or external stress was investigated. The results show that the critical diffusible hydrogen concentration of a blister forming is about 1.4×10^-5 , which is corresponding to the current density of 30 mA/cm^2 during cathodic charging in a sodium hydroxide solution. For a 0.1 cm thick sample, no matter the current density is equal to or much larger than the critical value, it spends at least about 132 h to form a hydrogen blister when hydrogen charging in single direction. It is approxi- mately equal to the time for hydrogen atom to diffuse throughout the sample, which exactly depends on the hydrogen diffusion coefficient and the penetration depth. The very first clear suggestion was reported that the incubation period for hydrogen blister nucleation was necessary. According to the Fick＇s laws, calculations show that the normalized hydrogen concentration in the escaping surface almost reaches 0.96 times of the charging surface, which means that the diffusion almost reaches a dynamic balance. A model was illustrated to describe the competitive relationship between hydrogen diffusion and blister formation.
文摘The model of hydrogen diffusion formerly de- veloped [1] has been applied successfully to the hydrogen permeation experiment results of three kinds of materials,α—Fe,Fe—Ti alloy and Fe—Ti—C alloy by the mathematical fitting method.From the fitting results it was shown that the model can re- fiect well the diffusion of hydrogen in the materials with trapping.The obtained trapping parameters(α and β)can be used to explain well the diffusion of hydrogen in the samples with trapping.
文摘The influence of alloy composition (Ti, Mn, TiN) on hydrogen diffusion in Fe was studied in detail using SCM-DV-Xα method. The voltage barriers were obtained via calculation on Fe clusters containing the alloy elements such as Ti, Mn as well as the chemical compound TiN respectively. The results showed that Ti element produced deep trap in Fe, decreasing the diffusion coefficient of hydrogen elements, Mn element did not produce deep trap in Fe, decreasing the diffusion coefficient slightly and TiN in Fe produced very deep "trap" decreasing the diffusion coefficient obviously. The calculation results were in agreement with experiment results.
文摘Hydrogen diffusion coefficients in amorphous Ti0.88Ni1.00 film were measured using electrochemical permeation technique. Diffusion coefficients increased with increasing hydrogen concentration. Activation energy of hydrogen diffusion was determined through measurement of the steady state anodic diffusion current density as a function of temperature, and an equation was derived to calculate the activation energy.
文摘A new model of hydrogen diffusion in metals has been developed,it is more efficient to describe the hydrogen diffusion with trapping in metals.In the model newly developed an impli- cit dependence on time of hydrogen diffusion coefficient in metals with trapping was firstly built and it is shown that hydrogen diffusion coefficient will be different at different posi- tions in a dynamic process of hydrogen diffusion in a metal. Numerical solutions of the present model were obtained by finite difference method.By changing the parameters in the model the diffusion of hydrogen in a metal and the effect of trapping were described and discussed.And the comparison between the well known McNabb and Foster's model and the present model was also made.
文摘The Proccss of gascous hydrogcn charging into a Ti_3Al- based alloy in the temperature range of 500-650℃isinvcstigatcd. The rcsnlls snoxvc that in rclatiollshil, between the average hydrogen concentration at constant tempreature and charging time reveals a parabolie rate law Applying the theory of lattice constant tcnlpcralurc and hrgillg tin rcvcals a parabolic riltc laiv. Applyillg tbcthcoly oftatticc dillbsio to allalyzc the hydrogcll diethesioll they andthat cncrgy of hydrogcn diffusion is 90.40 kJ/mol. and the equilibrium hydrogen content in the alloy depends on the temperature of the gaseous hydrogen charging process
文摘Hydrogen diffusion coefficients in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 alloy electrode as a function of state of charge (SOC) or temperature were determined by chronoamperometry. It is found that hydrogen diffusion coefficient decreases with the increase of SOC or the decrease of temperature. The activation energy for hydrogen diffusion in the alloy electrode with 50%SOC is evaluated to be 19.9?kJ/mol.
基金supported by the Korea Institute of Science and Technology(No.2E30993).
文摘Absorption and desorption processes of hydrogen in metals are facilitated by alloying elements;however,the formation of secondary phases often reduces storage capacity.The alloying effect on the hydrogen kinetics has been examined by time-lag permeation measurement,which lacks spatial resolution and yields the averaged diffusion coefficient from multiple phases.Here,we report an advanced scanning Kelvin probe force microscopy,combined with in-situ hydrogen loading system for submicron-scale measurement of diffusion kinetics in metals.Successive probing of the surface during hydrogen loading detects the temporal and spatial variations in the surface potential,enabling the estimation of diffusion coefficient.Not only for a single-phase magnesium but also for multiphase titaniumiron based alloys,we can obtain the diffusion coefficients of hydrogen in each phase.The estimated diffusion coefficients for TiFe alloys are higher than that for the pristine TiFe intermetallic compound,due to alloying elements that reduce the diffusion barrier and modify bond character.Our approach paves the way to the microscopic understanding of hydrogen diffusion in metals.
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.
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.
文摘In the present work. the hydrogen permeation and diffusion in two low-carbon steels. # 10 and #20. and 16Mn stee1 over the temperature range of 80 to 330℃ were investigated using gaseous permeation technique. The temperature dependence of hydrogen permeability. diffusivity and solubility for the three steels was obtained in the form of the Arrhenius equations. It was shown that the hydrogen permeability of the 16Mn steel is somewhat lower than that of the two low-carbon steels.whereas the hydrogen diffusivity is lowered in the order of #10, #20 and 16Mn but the activation energy of diffusion is much the same for the three steels. The difference in the diffusivity was attributed to the increase of ferrite-cementite interface areas with the refinement of pearlitic structure in the steels
