Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic materials.However,explanations for the observed HE phenomena are still under debate.To shed light on this issue,her...Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic materials.However,explanations for the observed HE phenomena are still under debate.To shed light on this issue,here we investigated the hydrogen-defect interaction by comparing the dislocation structure evolution after hydrogen adsorption and desorption in a Fe-28Mn-0.3C(wt%)twinning-induced plasticity steel with an austenitic structure using in situ electron channeling contrast imaging.The results indicate that hydrogen can strongly affect dislocation activities.In detail,hydrogen can promote the formation of stacking faults with a long dissociation distance.Besides,dislocation movements are frequently observed during hydrogen desorption.The required resolved shear stress is considered to be the residual stresses rendered by hydrogen segregation.Furthermore,the microstructural heterogeneity could lead to the discrepancy of dislocation activities even within the same materials.展开更多
Fatigue crack growth(FCG)tests were conducted on a medium-Mn steel annealed at two intercritical annealing temperatures,resulting in different austenite(γ)to fe rrite(α)phase fractions and differentγ(meta-)stabilit...Fatigue crack growth(FCG)tests were conducted on a medium-Mn steel annealed at two intercritical annealing temperatures,resulting in different austenite(γ)to fe rrite(α)phase fractions and differentγ(meta-)stabilities.Novel in-situ hydrogen plasma charging was combined with in-situ cyclic loading in an environmental scanning electron microscope(ESEM).The in-situ hydrogen plasma cha rging increased the fatigue crack growth rate(FCGR)by up to two times in comparison with the reference tests in vacuum.Fractographic investigations showed a brittle-like crack growth or boundary cracking manner in the hydrogen environment while a ductile transgranular manner in vacuum.For both materials,the plastic deformation zone showed a reduced size along the hydrogen-influenced fracture path in comparison with that in vacuum.The difference in the hydrogen-assisted FCG of the medium-Mn steel with different microstructures was explained in terms of phase fraction,phase stability,yielding strength and hydrogen distribution.This refined study can help to understand the FCG mechanism without or with hydrogen under in-situ hydrogen charging conditions and can provide some insights from the applications point of view.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(No.52101022)the Shaanxi Province Natural Science Foundation(No.2021JQ-080).
文摘Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic materials.However,explanations for the observed HE phenomena are still under debate.To shed light on this issue,here we investigated the hydrogen-defect interaction by comparing the dislocation structure evolution after hydrogen adsorption and desorption in a Fe-28Mn-0.3C(wt%)twinning-induced plasticity steel with an austenitic structure using in situ electron channeling contrast imaging.The results indicate that hydrogen can strongly affect dislocation activities.In detail,hydrogen can promote the formation of stacking faults with a long dissociation distance.Besides,dislocation movements are frequently observed during hydrogen desorption.The required resolved shear stress is considered to be the residual stresses rendered by hydrogen segregation.Furthermore,the microstructural heterogeneity could lead to the discrepancy of dislocation activities even within the same materials.
基金financially supported by the Department of Mechanical and Industrial Engineering(MTP),Norwegian University of Science and Technology(NTNU)the financial support of the Deutsche Forschungsgemeinschaft(DFG)within the Collaborative Research Center(SFB)761“Steel-ab initio:Quantum mechanics guided design of new Fe-based materials”。
文摘Fatigue crack growth(FCG)tests were conducted on a medium-Mn steel annealed at two intercritical annealing temperatures,resulting in different austenite(γ)to fe rrite(α)phase fractions and differentγ(meta-)stabilities.Novel in-situ hydrogen plasma charging was combined with in-situ cyclic loading in an environmental scanning electron microscope(ESEM).The in-situ hydrogen plasma cha rging increased the fatigue crack growth rate(FCGR)by up to two times in comparison with the reference tests in vacuum.Fractographic investigations showed a brittle-like crack growth or boundary cracking manner in the hydrogen environment while a ductile transgranular manner in vacuum.For both materials,the plastic deformation zone showed a reduced size along the hydrogen-influenced fracture path in comparison with that in vacuum.The difference in the hydrogen-assisted FCG of the medium-Mn steel with different microstructures was explained in terms of phase fraction,phase stability,yielding strength and hydrogen distribution.This refined study can help to understand the FCG mechanism without or with hydrogen under in-situ hydrogen charging conditions and can provide some insights from the applications point of view.
