1.Introduction Microbiologically influenced corrosion(MIC)is the destruction of metal materials caused by the activity of microorganisms and the participation of biofilms[1].Global economic costs caused by marine corr...1.Introduction Microbiologically influenced corrosion(MIC)is the destruction of metal materials caused by the activity of microorganisms and the participation of biofilms[1].Global economic costs caused by marine corrosion come to hundreds of billion dollars per year,with approximately 20% of corrosion losses caused by MIC[2].The MIC poses a serious threat to the integrity and safety of assets in the oil and gas industry,water industry,and nuclear waste storage facili-ties[3-5].展开更多
In-situ electron irradiation and aging are applied to introduce high-density precipitates in an Mg-10Gd-3Y-1Zn-0.5Zr(GWZ1031K,wt.%)alloy to improve the hardness.The results show that the hardness of the Mg alloy after...In-situ electron irradiation and aging are applied to introduce high-density precipitates in an Mg-10Gd-3Y-1Zn-0.5Zr(GWZ1031K,wt.%)alloy to improve the hardness.The results show that the hardness of the Mg alloy after irradiation for 10 h and aging for 9 h at 250℃ is 1.64 GPa,which is approximately 64% higher than that of the samples before being treated.It is mainly attributed to γ'precipitates on the basal plane after irradiation and the high-density nanoscale β'precipitates on the prismatic plane after aging,which should be closely related to the irradiation-induced homogenous clusters.The latter plays a key role in precipitation hardening.This result paves a way to improve the mechanical properties of metallic materials by tailoring the precipitation through irradiation and aging.展开更多
Using high-resolution transmission Kikuchi diffraction(TKD)and transmission electron microscopy(TEM),we examined the hierarchical clusters that form in situ in the heat-affected zone(HAZ),which are com-monly referred ...Using high-resolution transmission Kikuchi diffraction(TKD)and transmission electron microscopy(TEM),we examined the hierarchical clusters that form in situ in the heat-affected zone(HAZ),which are com-monly referred to as“ghost”structures,of bimodal titanium alloy Ti-5Al-2Sn-2Zr-4Mo-4Cr(wt%,TC17).The ghost structures are enriched with Al elements but poor in Mo and Cr compared to the surroundingβmatrix.TKD results show that the ghost structure in middle-HAZ mainly consists ofα_(L)laths with a high-angle grain boundary,which exhibits the classic Burgers orientation relationship(BOR)with the host matrix,while it encircles theα_(P)grains in far-HAZ.And the ghost structure is evidenced to form via in-complete martensitic transformation.TEM results further confirm that the ghost structure is composed ofαL and tinyβ_(L)laths with BOR,with the former being enriched with Al and poor with Cr and Mo,while the latter is the opposite.Interestingly,twoα_(L)variant clusters with a check-mark morphology are fre-quently observed viewed along[0001]_(αL)//[110]_(βL)directions,which are dominated by the crystallographic and geometrical relationships betweenαandβphases.Based on the microstructural characterization,it is hypothesized that the ghost structure is transformed from the initialα_(P)phase,due to the coupling ef-fect of high thermal stress(which induces the formation of a large number of dislocations)and element diffusion caused by sudden temperature increase and plunge cooling in the HAZ during the welding pro-cess.展开更多
Passive metals have superior resistance to general corrosion but are susceptible to pitting attack in certain aggressive media, leading to material failure with pronounced adverse economic and safety consequences. Ove...Passive metals have superior resistance to general corrosion but are susceptible to pitting attack in certain aggressive media, leading to material failure with pronounced adverse economic and safety consequences. Over the past decades, the mechanism of pitting corrosion has attracted corrosion community striving to study. However, the mechanism at the pitting initiation stage is still controversy, due to the difficulty encountered in obtaining precise experimental information with enough spatial resolution.Tracking the accurate sites where initial dissolution occurs as well as the propagation of the dissolution by means of multi-scale characterization is key to deciphering the link between microstructure and corrosion at the atomic scale and clarifying the pitting initiation mechanism. Here, we review our recent progresses in this issue by summarizing the results in three representative materials of 316F, and Super 304H stainless steel as well as 2024-Al alloy, using in situ ex-environmental TEM technique.展开更多
Cold-drawn pearlitic steel wire is irreplaceably used in industry owing to its outstanding mechanical property which is dominated by the cementite/ferrite(Fe_(3)C/Fe) interfaces in the material. However, the fine stru...Cold-drawn pearlitic steel wire is irreplaceably used in industry owing to its outstanding mechanical property which is dominated by the cementite/ferrite(Fe_(3)C/Fe) interfaces in the material. However, the fine structures of the Fe3C/Fe interfaces in the deformed wires are less known to date. In this work, transmission electron microscopic investigation was performed on the atomic structures of the interfaces with the Isaichev orientation relationship(OR) in the wires with progressive deformation strains. In addition to the effect of the dislocation/interface interactions, this work revealed that the deformation-induced partial decomposition of cementite plays an important role in the interface reconstruction during deformation. The interfacial carbon vacancies generated by cementite decomposition and particularly, the amorphization of cementite layers in the sample with ε > 1 could effectively annihilated the interfacial dislocations and consequently relaxed the interfacial stress. The correlations between the interface structure changes and the mechanical properties of the wires were discussed.展开更多
A newly developed severe plastic deformation （SPD） technique, i.e. repetitive upsetting （RU）, is employed to improve the strength and ductility of a Mg-Gd-Y-Zr alloy. During the RU processing, dynamic recrystalliz...A newly developed severe plastic deformation （SPD） technique, i.e. repetitive upsetting （RU）, is employed to improve the strength and ductility of a Mg-Gd-Y-Zr alloy. During the RU processing, dynamic recrystallization occurs in the Mg alloy, which leads to a significant grain refinement from 11.2 p.m to 2.8 μm. The yield strength （YS）, ultimate tensile strength （UTS） and elongation increase simultaneously with increasing RU passes. The microstructural evolution is affected by processing temperatures. Dynamic recrystallization prevails at low temperatures, while dynamic recovery is the main effect factor at high temperatures. Texture characteristics gradually become random during multiple passes of RU processing, which reduces the tension-compression asymmetry of the Mg-Gd-Y-Zr alloy. 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
Deformation kink is one of the important strengthening mechanisms of the long-period-stacking-ordered(LPSO)phase containing magnesium(Mg)alloys,while the deformation twin is generally suppressed.To optimize the mechan...Deformation kink is one of the important strengthening mechanisms of the long-period-stacking-ordered(LPSO)phase containing magnesium(Mg)alloys,while the deformation twin is generally suppressed.To optimize the mechanical properties of LPSO containing Mg alloy by simultaneously exciting kink and twin,we successfully prepared the Mg-Zn-Y-Zr alloy featuring intragranular LPSO phase and free grain boundary LPSO phase by homogenization.We unraveled the corresponding strengthening and toughening mechanisms through transmission electron microscopy characterization and theoretical analysis.The high strength and good plasticity of the homogenized alloy benefit from the synergistic deformation mechanism of multiple kinking and twining in the grains.And the activation of kinking and twinning depends on the thicknesses of LPSO lamellae and their relative spacing.These results may shed light on optimizing the design of Mg alloys regulating the microstructure of LPSO phases.展开更多
Heterostructured materials,defined as materials that contain multiple zones with dramatically different flow stresses,have the potential to push the envelope of the strength-ductility of metals and alloys beyond what ...Heterostructured materials,defined as materials that contain multiple zones with dramatically different flow stresses,have the potential to push the envelope of the strength-ductility of metals and alloys beyond what can be obtained conventionally[1–3].A prominent example is the heterogeneous lamella Ti that is as strong as its ultrafine-grained Ti,while as ductile as the coarsegrained Ti[4].展开更多
Formation of β’ phase in long-period stacking ordered(LPSO) structures in an Mg;Co;Y;(at.%) alloy after aging at 200 °C for 24 h or electron beam(EB) irradiation has been studied by high-angle annular dark-fiel...Formation of β’ phase in long-period stacking ordered(LPSO) structures in an Mg;Co;Y;(at.%) alloy after aging at 200 °C for 24 h or electron beam(EB) irradiation has been studied by high-angle annular dark-field scanning transmission electron microscopy(HAADFSTEM). β’ phase was precipitated only in the Mg matrix but not in LPSO structures after aging at 200 °C for 24 h. LPSO structure containing stacking defects transforms into the β’-long phase during EB irradiation, which plays a key role in accelerating solute atoms’ diffusion. New complex β’(LPSO) structures formed in the alloy after EB irradiation, such as β’(12 H) structure with an orthorhombic lattice(Mg;Y, Cmcm,a = 2 _(a0)= 0.642 nm, b=4√3_(a0), c = 6 _(c0)= 3.12 nm).展开更多
The role of melt cooling rate on the interface morphology and dislocation configuration between 18R long-period stacking ordered(LPSO)structure and Mg matrix in Mg_(97)Zn_(1)Y_(2)(at.%)alloys was investigated by atomi...The role of melt cooling rate on the interface morphology and dislocation configuration between 18R long-period stacking ordered(LPSO)structure and Mg matrix in Mg_(97)Zn_(1)Y_(2)(at.%)alloys was investigated by atomic-scale HAADF-STEM imaging.The 18R/Mg interface is step-like both in the near-equilibrium alloy and non-equilibrium alloy.Lower cooling rate makes the step size more regular and larger.Only 54R structure can be observed at the interface in the near-equilibrium alloy,and the dislocations are highly ordered.54R and 54R′structure sandwiched by b1 and b2+b3 dislocation arrays,and new dislocation configuration can be detected at the interface in the non-equilibrium alloy,but the dislocations are less ordered.18R/Mg interface containing 54R or 54R′in equilibrium width,parallel to the(010)plane,should be most stable based on elastic calculation.The segregation of solute atoms and its strong interaction with dislocations dominate the LPSO/Mg interface via diffusion-displacive transformation.展开更多
By Ar+ sputtering onto Si wafers which were surrounded by Mo plates, uniform cones over a large area on the Si surface were formed. Scanning electron microscopic study showed that the cones were formed on the entire s...By Ar+ sputtering onto Si wafers which were surrounded by Mo plates, uniform cones over a large area on the Si surface were formed. Scanning electron microscopic study showed that the cones were formed on the entire surface of the Si wafer. The dimensions of the uniform cones were one micrometer in diameter and 5-6 micrometers high. They were further characterized by means of cross-sectional transmission electron microscopy, with the technique of micro-diffractions. It was found that the cone contained a pure Si regime and a Mo-rich regime. In the binary Mo-Si zone, we identified three distinct areas vertically: (1) domains of Mo-induced Si ordered structures, (2) a small volume of a new Mo3Si2 structural variant, intergrown with the Si ordered structure, and (3) a small amount of pure Mo nanoparticles covering the surface of the cones. The formation of the large and uniform cones may provide a new surface configuration for potential applications in surface science and technology.展开更多
基金supported by the National Natural Science Foun-dation of China(Nos.52371071,51971228,and 51771212).
文摘1.Introduction Microbiologically influenced corrosion(MIC)is the destruction of metal materials caused by the activity of microorganisms and the participation of biofilms[1].Global economic costs caused by marine corrosion come to hundreds of billion dollars per year,with approximately 20% of corrosion losses caused by MIC[2].The MIC poses a serious threat to the integrity and safety of assets in the oil and gas industry,water industry,and nuclear waste storage facili-ties[3-5].
基金supported by the National Natural Science Foundation of China(Grant Nos.51871222,52171021,and 51801214)Liaoning Provincial Natural Science Foundation(2019-MS-335)the research fund of SYNL。
文摘In-situ electron irradiation and aging are applied to introduce high-density precipitates in an Mg-10Gd-3Y-1Zn-0.5Zr(GWZ1031K,wt.%)alloy to improve the hardness.The results show that the hardness of the Mg alloy after irradiation for 10 h and aging for 9 h at 250℃ is 1.64 GPa,which is approximately 64% higher than that of the samples before being treated.It is mainly attributed to γ'precipitates on the basal plane after irradiation and the high-density nanoscale β'precipitates on the prismatic plane after aging,which should be closely related to the irradiation-induced homogenous clusters.The latter plays a key role in precipitation hardening.This result paves a way to improve the mechanical properties of metallic materials by tailoring the precipitation through irradiation and aging.
基金supported by the National Natural Science Foun-dation of China(Grant Nos.51871222 and 52171021)Japan Soci-ety for the Promotion of Science(No.P20737)Natural Science Foundation of Liaoning Province(No.2023-MS-018).
文摘Using high-resolution transmission Kikuchi diffraction(TKD)and transmission electron microscopy(TEM),we examined the hierarchical clusters that form in situ in the heat-affected zone(HAZ),which are com-monly referred to as“ghost”structures,of bimodal titanium alloy Ti-5Al-2Sn-2Zr-4Mo-4Cr(wt%,TC17).The ghost structures are enriched with Al elements but poor in Mo and Cr compared to the surroundingβmatrix.TKD results show that the ghost structure in middle-HAZ mainly consists ofα_(L)laths with a high-angle grain boundary,which exhibits the classic Burgers orientation relationship(BOR)with the host matrix,while it encircles theα_(P)grains in far-HAZ.And the ghost structure is evidenced to form via in-complete martensitic transformation.TEM results further confirm that the ghost structure is composed ofαL and tinyβ_(L)laths with BOR,with the former being enriched with Al and poor with Cr and Mo,while the latter is the opposite.Interestingly,twoα_(L)variant clusters with a check-mark morphology are fre-quently observed viewed along[0001]_(αL)//[110]_(βL)directions,which are dominated by the crystallographic and geometrical relationships betweenαandβphases.Based on the microstructural characterization,it is hypothesized that the ghost structure is transformed from the initialα_(P)phase,due to the coupling ef-fect of high thermal stress(which induces the formation of a large number of dislocations)and element diffusion caused by sudden temperature increase and plunge cooling in the HAZ during the welding pro-cess.
基金supported financially by the National Natural Science Foundation of China (Nos. 51771212 and 11327901)the Innovation Fund in IMR (No. 2017-ZD05)
文摘Passive metals have superior resistance to general corrosion but are susceptible to pitting attack in certain aggressive media, leading to material failure with pronounced adverse economic and safety consequences. Over the past decades, the mechanism of pitting corrosion has attracted corrosion community striving to study. However, the mechanism at the pitting initiation stage is still controversy, due to the difficulty encountered in obtaining precise experimental information with enough spatial resolution.Tracking the accurate sites where initial dissolution occurs as well as the propagation of the dissolution by means of multi-scale characterization is key to deciphering the link between microstructure and corrosion at the atomic scale and clarifying the pitting initiation mechanism. Here, we review our recent progresses in this issue by summarizing the results in three representative materials of 316F, and Super 304H stainless steel as well as 2024-Al alloy, using in situ ex-environmental TEM technique.
基金financially supported by the National Natural Science Foundation of China (No. 51501195)the Fund of SYNL。
文摘Cold-drawn pearlitic steel wire is irreplaceably used in industry owing to its outstanding mechanical property which is dominated by the cementite/ferrite(Fe_(3)C/Fe) interfaces in the material. However, the fine structures of the Fe3C/Fe interfaces in the deformed wires are less known to date. In this work, transmission electron microscopic investigation was performed on the atomic structures of the interfaces with the Isaichev orientation relationship(OR) in the wires with progressive deformation strains. In addition to the effect of the dislocation/interface interactions, this work revealed that the deformation-induced partial decomposition of cementite plays an important role in the interface reconstruction during deformation. The interfacial carbon vacancies generated by cementite decomposition and particularly, the amorphization of cementite layers in the sample with ε > 1 could effectively annihilated the interfacial dislocations and consequently relaxed the interfacial stress. The correlations between the interface structure changes and the mechanical properties of the wires were discussed.
基金supported by the National Key R&D Program of China (grant number 2017YFA0204403)the National Natural Science Foundation of China (NSFC) under Grant Nos. 51601003, 51301092, 51404151, 51401172+1 种基金Project supported by Beijing Postdoctoral Research Foundation under Grant No. 2016ZZ-02Project of Science & Technology Department of Sichuan Province (No. 2015HH0012)
文摘A newly developed severe plastic deformation （SPD） technique, i.e. repetitive upsetting （RU）, is employed to improve the strength and ductility of a Mg-Gd-Y-Zr alloy. During the RU processing, dynamic recrystallization occurs in the Mg alloy, which leads to a significant grain refinement from 11.2 p.m to 2.8 μm. The yield strength （YS）, ultimate tensile strength （UTS） and elongation increase simultaneously with increasing RU passes. The microstructural evolution is affected by processing temperatures. Dynamic recrystallization prevails at low temperatures, while dynamic recovery is the main effect factor at high temperatures. Texture characteristics gradually become random during multiple passes of RU processing, which reduces the tension-compression asymmetry of the Mg-Gd-Y-Zr alloy. 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
基金This work was supported by the National Natural Science Foundation of China(Grant No.52101015,52171021,and 51871222)Natural Science Foundation of Hebei Province(Grant No.E2020208083)Science and Technology Research Project of Colleges and Universities in Hebei Province(Grant No.BJK2022020).
文摘Deformation kink is one of the important strengthening mechanisms of the long-period-stacking-ordered(LPSO)phase containing magnesium(Mg)alloys,while the deformation twin is generally suppressed.To optimize the mechanical properties of LPSO containing Mg alloy by simultaneously exciting kink and twin,we successfully prepared the Mg-Zn-Y-Zr alloy featuring intragranular LPSO phase and free grain boundary LPSO phase by homogenization.We unraveled the corresponding strengthening and toughening mechanisms through transmission electron microscopy characterization and theoretical analysis.The high strength and good plasticity of the homogenized alloy benefit from the synergistic deformation mechanism of multiple kinking and twining in the grains.And the activation of kinking and twinning depends on the thicknesses of LPSO lamellae and their relative spacing.These results may shed light on optimizing the design of Mg alloys regulating the microstructure of LPSO phases.
基金supported by the US Army Research Office[W911 NF-12-1-0009]financial support from the National Science Foundation(NSF)under award no.1929646performed in part at the AIF facility,which is supported by the State of North Carolina and the National Science Foundation[ECCS-1542015]
文摘Heterostructured materials,defined as materials that contain multiple zones with dramatically different flow stresses,have the potential to push the envelope of the strength-ductility of metals and alloys beyond what can be obtained conventionally[1–3].A prominent example is the heterogeneous lamella Ti that is as strong as its ultrafine-grained Ti,while as ductile as the coarsegrained Ti[4].
基金supported by the National Natural Science Foundation of China(Grant No.51801214 and 51871222)。
文摘Formation of β’ phase in long-period stacking ordered(LPSO) structures in an Mg;Co;Y;(at.%) alloy after aging at 200 °C for 24 h or electron beam(EB) irradiation has been studied by high-angle annular dark-field scanning transmission electron microscopy(HAADFSTEM). β’ phase was precipitated only in the Mg matrix but not in LPSO structures after aging at 200 °C for 24 h. LPSO structure containing stacking defects transforms into the β’-long phase during EB irradiation, which plays a key role in accelerating solute atoms’ diffusion. New complex β’(LPSO) structures formed in the alloy after EB irradiation, such as β’(12 H) structure with an orthorhombic lattice(Mg;Y, Cmcm,a = 2 _(a0)= 0.642 nm, b=4√3_(a0), c = 6 _(c0)= 3.12 nm).
基金This work is supported by the National Natural Science Foundation of China(grant number 51801214 and 51871222)Guangxi Science and Technology Base and Talents Special Project(Guike AD20297034)+2 种基金Liaoning Provincial Natural Science Foundation(2019-MS-335)Research Start-up Funding from Guangxi University of Science and Technology(No.03200150)Natural Science Foundation of Hebei Province of China(grant number E2020208083).
文摘The role of melt cooling rate on the interface morphology and dislocation configuration between 18R long-period stacking ordered(LPSO)structure and Mg matrix in Mg_(97)Zn_(1)Y_(2)(at.%)alloys was investigated by atomic-scale HAADF-STEM imaging.The 18R/Mg interface is step-like both in the near-equilibrium alloy and non-equilibrium alloy.Lower cooling rate makes the step size more regular and larger.Only 54R structure can be observed at the interface in the near-equilibrium alloy,and the dislocations are highly ordered.54R and 54R′structure sandwiched by b1 and b2+b3 dislocation arrays,and new dislocation configuration can be detected at the interface in the non-equilibrium alloy,but the dislocations are less ordered.18R/Mg interface containing 54R or 54R′in equilibrium width,parallel to the(010)plane,should be most stable based on elastic calculation.The segregation of solute atoms and its strong interaction with dislocations dominate the LPSO/Mg interface via diffusion-displacive transformation.
文摘By Ar+ sputtering onto Si wafers which were surrounded by Mo plates, uniform cones over a large area on the Si surface were formed. Scanning electron microscopic study showed that the cones were formed on the entire surface of the Si wafer. The dimensions of the uniform cones were one micrometer in diameter and 5-6 micrometers high. They were further characterized by means of cross-sectional transmission electron microscopy, with the technique of micro-diffractions. It was found that the cone contained a pure Si regime and a Mo-rich regime. In the binary Mo-Si zone, we identified three distinct areas vertically: (1) domains of Mo-induced Si ordered structures, (2) a small volume of a new Mo3Si2 structural variant, intergrown with the Si ordered structure, and (3) a small amount of pure Mo nanoparticles covering the surface of the cones. The formation of the large and uniform cones may provide a new surface configuration for potential applications in surface science and technology.
