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
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
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.
