This study investigates the stress corrosion cracking(SCC)behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.%NaCl solution using slow strain rate tensile(SSRT)testing.The results reveal that SCC suscepti-bility increase...This study investigates the stress corrosion cracking(SCC)behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.%NaCl solution using slow strain rate tensile(SSRT)testing.The results reveal that SCC suscepti-bility increases as the strain rate decreases,with hydrogen embrittlement(HE)becoming more dominant at lower strain rates,leading to brittle fracture.Anodic dissolution(AD)plays a more significant role at higher strain rates,resulting in mixed fracture modes.Additionally,the mechanical properties and SCC resistance are strongly influenced by the sample orientation.TD-oriented samples show higher SCC susceptibility than RD-oriented ones due to the alignment of Gd-and Y-rich precipitates and grain boundaries,which act as initiation sites for SCC.These precipitates form micro-galvanic couples with the Mg matrix,accelerating localized corrosion and HE.The findings provide insights into the SCC mechanisms of VW83 alloy and highlight the importance of optimizing microstructure and processing conditions to improve its corrosion resistance.展开更多
Implants are inevitably subjected to stress corrosion,bringing serious challenges to the controlled degradation of biomedical Mg alloys.It is worth studying the stress corrosion cracking(SCC)behavior of Mg alloy and e...Implants are inevitably subjected to stress corrosion,bringing serious challenges to the controlled degradation of biomedical Mg alloys.It is worth studying the stress corrosion cracking(SCC)behavior of Mg alloy and exploring Mg alloy with good SCC resistance for wide biomedical applications.In this work,the as-cast and as-extruded Mg-3Gd-1Zn-0.4Zr(GZ31K)alloys with uniform corrosion were used to investigate SCC behavior.The as-extruded GZ31K alloy exhibited better corrosion resistance and mechanical properties than the as-cast one mainly owing to grain refinement and uniformly distributed fine precipitates,and possessed superior SCC resistance.To clarify the SCC mechanism,the slow strain rate tests were assisted with applied constant potentials via an electrochemical workstation.Accelerated anodic dissolution at anodic polarization deteriorated SCC resistance due to the initiation of corrosion pits and micro-cracks.However,cathodic polarization had no obvious effects on SCC resistance,along with both retarded corrosion and accelerated hydrogen evolution.Stacking faults in GZ31K alloy were hydrogen capture containers to reduce the effect of hydrogen on SCC resistance during cathodic polarization.These findings provide new insights into the evaluation of SCC mechanism,and offer more opportunities to explore Mg alloys with good SCC resistance by regulating anodic dissolution.展开更多
The effect of aging precipitation on the stress corrosion cracking(SCC)mechanism of Ni(Fe,Al)-maraging steel was studied through the comparative characterization and analyses of the microstructures and fracture featur...The effect of aging precipitation on the stress corrosion cracking(SCC)mechanism of Ni(Fe,Al)-maraging steel was studied through the comparative characterization and analyses of the microstructures and fracture features of solid–solution and peak-aged steels.Aging precipitation exerts a chain of impacts on the deformative compatibility and electrochemical difference between the matrix and oth-er phases or interfaces.The strength of the martensite matrix is enhanced by abundant and evenly dispersed Ni(Fe,Al)precipitates,thereby reducing the possibility of splitting across martensite laths.Meanwhile,the Volta potential difference(VPD)between the matrix and primary NbC particles increases from 11.43 to 18.60 mV.Given that most of the primary NbC particles tend to be distributed along high-angle grain boundaries(HAGBs),anodic dissolution along HAGBs accelerates.Therefore,mechanical and electrochemical factors triggered by aging precipitation are involved in the variation in SCC behavior and mechanism.The SCC susceptibility of the steel in-creases along with the increasing tendency for intergranular cracking.展开更多
A series of Sn microalloying high-strength low-alloy(HSLA)steels were prepared through vacuum melting and hot rolling.Their stress corrosion cracking(SCC)behavior under high Cl^(−)environments was investigated using U...A series of Sn microalloying high-strength low-alloy(HSLA)steels were prepared through vacuum melting and hot rolling.Their stress corrosion cracking(SCC)behavior under high Cl^(−)environments was investigated using U-bend immersion,slow strain rate testing,electrochemical methods,and novel SCC sensor.Results revealed that HSLA steel microalloying with 0.1 wt.%Sn demonstrated superior SCC resistance,primarily attributed to the effective inhibition of the anodic dissolution mechanism.Fracture morphology revealed a transformation in fracture mode from brittle to a mixture of brittle-ductile characteristics,accompanied by the formation of a protective SnO_(2)oxide film on the steel surface.However,excessive Sn content exacerbated SCC susceptibility due to the increased hydrolysis of Sn^(2+),leading to localized pitting and crack initiation.The critical role of optimal Sn content was highlighted in balancing mechanical properties and corrosion resistance,suggesting potential applications in industries where materials face harsh chloride environments.展开更多
Though magnesium(Mg)alloys are highly attractive for their use as biodegradable/temporary implants,they can be critically compromised in such applications due to their susceptibility to corrosion and stress corrosion ...Though magnesium(Mg)alloys are highly attractive for their use as biodegradable/temporary implants,they can be critically compromised in such applications due to their susceptibility to corrosion and stress corrosion cracking(SCC)in human body fluid(such as Hanks’solution).This study investigated the role of additions of bovine serum albumin(BSA)and glucose to Hanks’solution in SCC of a Mg alloy,ZK60.The study reproducibly demonstrated the novel and unique characteristic of the acutely elliptical shape of the overall fracture surface of alloy subjected to SCC tests,exclusively when BSA was added to the Hanks’solution,whereas tests in the Hanks’solution without BSA produced the fracture surface of usual circular shape.Also,the BSA addition to the Hanks’solution produced contrasting influences on SCC and electrochemical corrosion.The study provides a comprehensive mechanistic explanation for the two phenomena.展开更多
This study explored the coupling effects of microstructure,strain rate,and 3.5%NaCl solution on stress corrosion cracking(SCC)behaviors of low-cost Ti6411 and Ti52 titanium alloys,compared to those of marine TC4ELI an...This study explored the coupling effects of microstructure,strain rate,and 3.5%NaCl solution on stress corrosion cracking(SCC)behaviors of low-cost Ti6411 and Ti52 titanium alloys,compared to those of marine TC4ELI and Ti80 titanium alloys.Slow strain rate tensile(SSRT)tests were performed to evaluate SCC susceptibility.The SCC susceptibility index(I_(SSRT))was calculated,and the fracture morphologies were investigated to clarify the stress corrosion mechanisms.The experimental results show that the ISSRT of Ti6411 titanium alloy with a lamellar micro structure(LM)is the highest under a strain rate of 1×10^(-6)s^(-1),and the corresponding fracture mode shows a quasi-cleavage fracture with low ductility.TC4ELI alloy with an equiaxed microstructure exhibits excellent SCC resistance.However,the SCC behavior of the Ti80 alloy with a bimodal microstructure is relatively sensitive to high strain rates,and the Ti52 tube with a typical Widmanst?tten microstructure is sensitive to low strain rates.The stress corrosion mechanism can be attributed to the cyclic process of passive film rupture,anodic dissolution,and hydrogen-induced cracking due to a multifactor comprehensive interaction corresponding to specific microstructures,strain rates,and corrosive media.The LM of the Ti6411 plate allowed easy chloride penetration into the bare metal,thereby reducing the protection of the film and resulting in continuous anodic dissolution and hydrogen accumulation at the crack tip.The coupled effect of the internal hydrogen pressure and external tensile stress can easily cause crack propagation and failure under service conditions.展开更多
The strength of traditional Al-Mg alloys primarily depends on cold deformation and increasing Mg content,but it can become susceptible to stress corrosion cracking(SCC)when the Mg content is high(>3 wt.%).Simultane...The strength of traditional Al-Mg alloys primarily depends on cold deformation and increasing Mg content,but it can become susceptible to stress corrosion cracking(SCC)when the Mg content is high(>3 wt.%).Simultaneous optimizing strength and SCC resistance in Al-Mg alloys is challenging.This study introduces a nanostructured Al-10Mg(10 wt.%)alloy with improved strength and SCC resistance by dynamic plastic deformation and optimized annealing.The as-deformed sample exhibits a nano-scaled lamellar structure.With rising annealing temperatures,structure size of the alloy increases while dislocation density decreases,transitioning lamellar to equiaxed grains.Nanostructured Al-10Mg alloys annealed at 250°C exhibit superior mechanical properties and reduced SCC susceptibility at sensitization state.The high fraction of low-angle grain boundaries with a reduction in dislocation density can effectively suppress the nucleation and growth of grain boundary precipitates(GBPs)during sensitization,thereby maintaining a relatively low GBPs coverage.The results provide guidance for designing Al-Mg alloys that are stronger and more resistant to SCC with higher Mg content.展开更多
Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding condit...Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding conditions are insufficient.Here,the stress corrosion cracking(SCC)behavior of base metal(BM)and weld zone(WZ)of TIG welded Al-Mg-Mn-Sc-Zr alloys was investigated by using pre-cracked compact tensile samples immersed in 3.5%NaCl solution.The direct current potential drop(DCPD)method was used to record the crack propagation.The microstructure and fracture morphology of different regions of TIG welded joints were studied by SEM,EBSD and TEM,and the SCC crack propagation mechanism of BM and WZ was analyzed.The results demonstrated that the critical stress intensity factor for stress corrosion cracking(K_(ⅠSCC))of BM and WZ was 7.05 MPa·m_(1/2) and 11.79 MPa·m_(1/2),respectively.Then,the crack propagation rate of BM was faster than that of WZ,and BM was more susceptible to SCC than WZ.Additionally,the fracture mode of the BM mainly exhibited transgranular fracture,while the fracture mode of the WZ mainly exhibited intergranular and transgranular mixed fracture.Moreover,SCC crack propagation was attributed to the combined effect of anodic dissolution and hydrogen embrittlement.This study will provide experimental and theoretical basis for the wide application of TIG welded Al-Mg-Mn-Sc-Zr alloys in aerospace.展开更多
The influences of heat treatment on stress corrosion cracking （SCC）, fracture toughness and strength of 7085 aluminum alloy were investigated by slow strain rate testing, Kahn tear testing combined with scanning ele...The influences of heat treatment on stress corrosion cracking （SCC）, fracture toughness and strength of 7085 aluminum alloy were investigated by slow strain rate testing, Kahn tear testing combined with scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results show that the fracture toughness of T74 overaging is increased by 22.9% at the expense of 13.6% strength, and retrogression and reaging （RRA） enhances fracture toughness 14.2% without reducing the strength compared with T6 temper. The fracture toughness of dual-retrogression and reaging （DRRA） is equivalent to that of T74 with an increased strength of 14.6%. The SCC resistance increases in the order： T6〈RRA〈DRRA≈T74. The differences of fracture toughness and SCC were explained on the basis of the role of matrix precipitates and grain boundary orecioitates.展开更多
Evolution of microstructure and stress corrosion cracking （SCC） susceptibility of 7050 aluminum alloy with 0.094%, 0.134% and 0.261% Si （mass fraction） in T7651 condition have been investigated. The results show t...Evolution of microstructure and stress corrosion cracking （SCC） susceptibility of 7050 aluminum alloy with 0.094%, 0.134% and 0.261% Si （mass fraction） in T7651 condition have been investigated. The results show that the area fraction of Mg2Si increases from 0.16% to 1,48% and the size becomes coarser, while the area fraction of the other coarse phases including Al2CuMg, Mg（Al,Cu,Zn）2 and A17Cu2Fe decreases from 2.42% to 0.78% with Si content increasing from 0.094% to 0.261%. The tensile strength and elongation of 7050-T7651 alloys is decreased with the increase of Si content by slow strain rate test （SSRT） in ambient air. However, electrical conductivity is improved and SCC susceptibility is reduced with the increase of Si content by SSRT in corrosion environment with 3.5% NaCl solution.展开更多
The stress corrosion cracking（SCC） behaviour of 7A52 aluminum alloy in air and in 3.5% NaCl solution was researched by slow strain rate test（SSRT） and SEM-EDS. The SCC susceptibility was estimated with the loss of...The stress corrosion cracking（SCC） behaviour of 7A52 aluminum alloy in air and in 3.5% NaCl solution was researched by slow strain rate test（SSRT） and SEM-EDS. The SCC susceptibility was estimated with the loss of the reduction in area. The experimental results indicate that the SCC susceptibility of 7A52 aluminum alloy in 3.5% chloride solution is the highest at strain rate of 1×10-6 s-1. The lowest one is under the condition of 1×10-5 s-1. Stress concentration and anode dissolving around Al-Fe-Mn intermetallics initiate micropores which will result in microcracks. The existence of intermetallics in the microstructure may play an important role in understanding the SCC initiation mechanisms of 7A52 aluminum alloy.展开更多
Stress corrosion cracking （SCC） is degradation of mechanical properties under the combined action of stress and corrosive environment of the susceptible material. Out of eight series of aluminium alloys, 2xxx, 5xxx...Stress corrosion cracking （SCC） is degradation of mechanical properties under the combined action of stress and corrosive environment of the susceptible material. Out of eight series of aluminium alloys, 2xxx, 5xxx and 7xxx aluminium alloys are susceptible to SCC. Among them, 7xxx series aluminium alloys have specific application in aerospace, military and structural industries due to superior mechanical properties. In these high strength 7xxx aluminium alloys, SCC plays a vital factor of consideration, as these failures are catastrophic during the service. The understanding of SCC behaviour possesses critical challenge for this alloy. The main aim of this review paper is to understand the effect of constituent alloying elements on the response of microstructural variation in various heat-treated conditions on SCC behavior. Further, review was made for improving the SCC resistance using thermomechanical treatments and by surface modifications of 7xxx alloys. Apart from a brief review on SCC of 7xxx alloys, this paper presents the effect of stress and pre-strain, effect of constituent alloying elements in the alloy, and the effect of environments on SCC behaviour. In addition, the SCC behaviours of weldments, 7xxx metal matrix composites and also laser surface modifications were also reviewed.展开更多
Hydrogen was a key factor resulting in stress corrosion cracking （SCC） of X80 pipeline steel in Ku＇erle soil simulated solution. In this article, the effect of hydrogen on the SCC susceptibility of X80 steel was in...Hydrogen was a key factor resulting in stress corrosion cracking （SCC） of X80 pipeline steel in Ku＇erle soil simulated solution. In this article, the effect of hydrogen on the SCC susceptibility of X80 steel was investigated further by slow strain rate tensile test, the surface fractures were observed using scanning electron microscopy （SEM）, and the fracture mechanism of SCC was discussed. The results indicate that hydrogen increases the SCC susceptibility. The SEM micrographs of hydrogen precharged samples presents a brittle quasi-cleavage feature, and pits facilitate the transgranular crack initiation. In the electrochemical impedance spectroscopy （EIS） measurement, the decreased polarization resistance and the pitting resistance of samples with hydrogen indicate that hydrogen increases the dissolution rate and deteriorates the pitting corrosion resistance. The potentiodynamic polarization curves present that hydrogen also accelerates the dissolution rate of the crack tip.展开更多
Influence of Sc content on microstructure and stress corrosion cracking behavior of medium strength AI-Zn-Mg alloy have been investigated by optical microscopy, scanning electron microscopy, electron backscatter diffr...Influence of Sc content on microstructure and stress corrosion cracking behavior of medium strength AI-Zn-Mg alloy have been investigated by optical microscopy, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and slow strain rate test. The results indicate that the addition of Sc results in the formation of the quaternary coherent AI3（Sc, Zr, Ti） dispersoids during homogenization treatment, which will inhibit the dynamic recrystallization behavior. The number density ofAl3（Sc, Zr, Ti） particles increases with the increase of Sc content, and thus the recrystallization fraction of hot-extruded alloy is reduced and the peak strength in two-stage artificial aging sample is enhanced. At the same time, the wide of precipitation free zone is reduced, and the content of Zn and Mg in grain boundary particles and precipitation free zone is increased with the increase of Sc content. In peak-aged state, the 0.06 wt% Sc added alloy shows the better stress corrosion cracking resistance than the Sc-free alloy because of the reduction of recrystallization fraction and the interrupted distribution of grain boundary precipitates along grain boundary. However, the further addition of Sc to 0.11 wt% will result in the deterioration of stress corrosion cracking resistance due to the increase of electrochemical activity of grain boundary particles and precipitation free zone as well as hydrogen embrittlement.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
5083 Al alloy sheets with different grain sizes(8.7-79.2 μm) were obtained by cold rolling and annealing. Their microstructures, intergranular corrosion(IGC), stress corrosion cracking(SCC), and crack propagation beh...5083 Al alloy sheets with different grain sizes(8.7-79.2 μm) were obtained by cold rolling and annealing. Their microstructures, intergranular corrosion(IGC), stress corrosion cracking(SCC), and crack propagation behaviors were investigated. The results showed that samples with coarse grains exhibit better IGC resistance with a corrosion depth of 15 μm. The slow strain rate test results revealed that fine-grained samples exhibit better SCC resistance with a susceptibility index(ISSRT) of 11.2%. Furthermore, based on the crack propagation mechanism, grain refinement can improve the SCC resistance by increasing the number of grain boundaries to induce the corrosion crack propagation along a tortuous path. The grains with {011} orientation could hinder crack propagation by orientating it toward the low-angle grain boundary region. The crack in the fine-grained material slowly propagates due to the tortuous path, and low H;and Cl;concentrations.展开更多
The influence of quenching rate on microstructure and stress corrosion cracking （SCC） of 7085 aluminum alloy was investigated by tensile test, slow strain rate test （SSRT）, combined with scanning electron microsco...The influence of quenching rate on microstructure and stress corrosion cracking （SCC） of 7085 aluminum alloy was investigated by tensile test, slow strain rate test （SSRT）, combined with scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and electrochemical test. The results show that with decreasing the quenching rate, the size and inter-particle distance of the grain boundary precipitates as well as precipitation free zone width increase, but the copper content of grain boundary precipitates decreases. The SCC resistance of the samples increases first and then decreases, which is attributed to the copper content, size and distribution of grain boundary precipitates.展开更多
Different artificial two-stage ageing behaviors and their effect on stress corrosion cracking （SCC） susceptibility of AI-Zn-Mg alloy have been investigated. The experimental results show that two hardness peaks pres...Different artificial two-stage ageing behaviors and their effect on stress corrosion cracking （SCC） susceptibility of AI-Zn-Mg alloy have been investigated. The experimental results show that two hardness peaks present on the second-stage ageing-hardening curve when the first-stage ageing is dealt with comparatively lower temperature than the conventional one. The first peak is caused by dispersive and evenly distributed G.P. zones, while η ′phases and coarsened G.P. zones contribute to the second peak. Tensile strength of experimental alloy raises 9.6% （33.2 MPa） and SCC susceptibility decreases 38.9% by applying the second peak ageing regime instead of conventional T73. AI-Zn-Mg alloy obtains high strength and SCC resistance due to its finely dispersive matrix precipitates （MPts）, coarsened and discontinuous grain boundary precipitates （GBPs）, as well as the narrow precipitate free zone （PFZ） in the second peak ageing condition. 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
The correlations among the corrosion behaviour,grain-boundary microchemistry,and Zn content in Al-Zn-Mg-Cu alloys were studied using stress corrosion cracking(SCC)and intergranular corrosion(IGC)tests,combined with sc...The correlations among the corrosion behaviour,grain-boundary microchemistry,and Zn content in Al-Zn-Mg-Cu alloys were studied using stress corrosion cracking(SCC)and intergranular corrosion(IGC)tests,combined with scanning electron microscopy(SEM)and high-angle angular dark field scanning transmission electron microscopy(HAADF-STEM)microstructural examinations.The results showed that the tensile strength enhancement of high Zn-containing Al-Zn-Mg-Cu alloys was mainly attributed to the high density nano-scale matrix precipitates.The SCC plateau velocity for the alloy with 11.0 wt.%Zn was about an order of magnitude greater than that of the alloy with 7.9 wt.%Zn,which was mainly associated with Zn enrichment in grain boundary precipitates and wide precipitates-free zones.The SCC mechanisms of different Zn-containing alloys were discussed based on fracture features,grain-boundary microchemistry,and electrochemical properties.展开更多
The effects of pre-deformation and strain rate on the stress corrosion cracking （SCC） behavior of aluminum alloy 2519 in air and in 3.5% NaCI water solution were investigated by means of slow strain rate tension （S...The effects of pre-deformation and strain rate on the stress corrosion cracking （SCC） behavior of aluminum alloy 2519 in air and in 3.5% NaCI water solution were investigated by means of slow strain rate tension （SSRT）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results indicate that the alloy is susceptible to SCC in 3.5% NaCI water solution and not in air. At the same pre-deformation, the alloy is more susceptible to SCC at 1.33 × 10^-5 s^-1 than at 6.66 × 10^-5 s^-1. Moreover, it is more susceptible to SCC at free pre-deformation than at 10% pre-deformation at the same strain rate. The number of 0 precipitated along the grain boundaries is reduced and distributed discontinuously, at the same time, the precipitate-free zones （PFZ） become narrow and the susceptibility to stress corrosion cracking is reduced after 10% pre-deformation.展开更多
Constant load tests in NS4 solution purged with N2-5%CO2 gas mixture were conducted on American Petroleum Institute （API） X80 pipeline steel applied in the 2nd West-East （;as Pipeline project with and without prelo...Constant load tests in NS4 solution purged with N2-5%CO2 gas mixture were conducted on American Petroleum Institute （API） X80 pipeline steel applied in the 2nd West-East （;as Pipeline project with and without preload. The results show that cracks could initiate and propagate in X80 pipeline steel in near-neutral pH environment under a constant load condition. The life of crack initiation and propagation increased with decreasing applied stress. Preload did not change its corrosion behavior obviously. However, preload reduced the time for crack initiation.展开更多
基金the National Natural Science Foundation of China(Nos.52471012,52471043).
文摘This study investigates the stress corrosion cracking(SCC)behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.%NaCl solution using slow strain rate tensile(SSRT)testing.The results reveal that SCC suscepti-bility increases as the strain rate decreases,with hydrogen embrittlement(HE)becoming more dominant at lower strain rates,leading to brittle fracture.Anodic dissolution(AD)plays a more significant role at higher strain rates,resulting in mixed fracture modes.Additionally,the mechanical properties and SCC resistance are strongly influenced by the sample orientation.TD-oriented samples show higher SCC susceptibility than RD-oriented ones due to the alignment of Gd-and Y-rich precipitates and grain boundaries,which act as initiation sites for SCC.These precipitates form micro-galvanic couples with the Mg matrix,accelerating localized corrosion and HE.The findings provide insights into the SCC mechanisms of VW83 alloy and highlight the importance of optimizing microstructure and processing conditions to improve its corrosion resistance.
基金supported by the National Natural Science Foundation of China(52071175,52301304)the Natural Science Foundation of Jiangsu Province(BK20230704)+3 种基金the China Postdoctoral Science Foundation Funded Project(2023M731742)the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province(23KJB430019)the Research Fund of Nanjing Institute of Technology(YKJ202402)the Open Research Fund of Jiangsu Key Laboratory for Light Metal Alloys(LMA202401).
文摘Implants are inevitably subjected to stress corrosion,bringing serious challenges to the controlled degradation of biomedical Mg alloys.It is worth studying the stress corrosion cracking(SCC)behavior of Mg alloy and exploring Mg alloy with good SCC resistance for wide biomedical applications.In this work,the as-cast and as-extruded Mg-3Gd-1Zn-0.4Zr(GZ31K)alloys with uniform corrosion were used to investigate SCC behavior.The as-extruded GZ31K alloy exhibited better corrosion resistance and mechanical properties than the as-cast one mainly owing to grain refinement and uniformly distributed fine precipitates,and possessed superior SCC resistance.To clarify the SCC mechanism,the slow strain rate tests were assisted with applied constant potentials via an electrochemical workstation.Accelerated anodic dissolution at anodic polarization deteriorated SCC resistance due to the initiation of corrosion pits and micro-cracks.However,cathodic polarization had no obvious effects on SCC resistance,along with both retarded corrosion and accelerated hydrogen evolution.Stacking faults in GZ31K alloy were hydrogen capture containers to reduce the effect of hydrogen on SCC resistance during cathodic polarization.These findings provide new insights into the evaluation of SCC mechanism,and offer more opportunities to explore Mg alloys with good SCC resistance by regulating anodic dissolution.
基金support from the National Key Research and Development Program of China(No.2023YFB3710300)National Natural Science Foundation of China(Nos.12174296 and 52101088)+1 种基金Major Program(JD)of Hubei Province,China(No.2023BAA019-5)Numerical calculation is supported by the High-Performance Computing Center of Wuhan University of Science and Technology,China.
文摘The effect of aging precipitation on the stress corrosion cracking(SCC)mechanism of Ni(Fe,Al)-maraging steel was studied through the comparative characterization and analyses of the microstructures and fracture features of solid–solution and peak-aged steels.Aging precipitation exerts a chain of impacts on the deformative compatibility and electrochemical difference between the matrix and oth-er phases or interfaces.The strength of the martensite matrix is enhanced by abundant and evenly dispersed Ni(Fe,Al)precipitates,thereby reducing the possibility of splitting across martensite laths.Meanwhile,the Volta potential difference(VPD)between the matrix and primary NbC particles increases from 11.43 to 18.60 mV.Given that most of the primary NbC particles tend to be distributed along high-angle grain boundaries(HAGBs),anodic dissolution along HAGBs accelerates.Therefore,mechanical and electrochemical factors triggered by aging precipitation are involved in the variation in SCC behavior and mechanism.The SCC susceptibility of the steel in-creases along with the increasing tendency for intergranular cracking.
基金support of the National Natural Science Foundation of China(No.52171063).
文摘A series of Sn microalloying high-strength low-alloy(HSLA)steels were prepared through vacuum melting and hot rolling.Their stress corrosion cracking(SCC)behavior under high Cl^(−)environments was investigated using U-bend immersion,slow strain rate testing,electrochemical methods,and novel SCC sensor.Results revealed that HSLA steel microalloying with 0.1 wt.%Sn demonstrated superior SCC resistance,primarily attributed to the effective inhibition of the anodic dissolution mechanism.Fracture morphology revealed a transformation in fracture mode from brittle to a mixture of brittle-ductile characteristics,accompanied by the formation of a protective SnO_(2)oxide film on the steel surface.However,excessive Sn content exacerbated SCC susceptibility due to the increased hydrolysis of Sn^(2+),leading to localized pitting and crack initiation.The critical role of optimal Sn content was highlighted in balancing mechanical properties and corrosion resistance,suggesting potential applications in industries where materials face harsh chloride environments.
基金funded by Monash University,AustraliaDepartment of Biotechnology,India through IITB-Monash Research Academy.
文摘Though magnesium(Mg)alloys are highly attractive for their use as biodegradable/temporary implants,they can be critically compromised in such applications due to their susceptibility to corrosion and stress corrosion cracking(SCC)in human body fluid(such as Hanks’solution).This study investigated the role of additions of bovine serum albumin(BSA)and glucose to Hanks’solution in SCC of a Mg alloy,ZK60.The study reproducibly demonstrated the novel and unique characteristic of the acutely elliptical shape of the overall fracture surface of alloy subjected to SCC tests,exclusively when BSA was added to the Hanks’solution,whereas tests in the Hanks’solution without BSA produced the fracture surface of usual circular shape.Also,the BSA addition to the Hanks’solution produced contrasting influences on SCC and electrochemical corrosion.The study provides a comprehensive mechanistic explanation for the two phenomena.
基金the financial support from the National Key R&D Program of China(No.2022YFB3705605)。
文摘This study explored the coupling effects of microstructure,strain rate,and 3.5%NaCl solution on stress corrosion cracking(SCC)behaviors of low-cost Ti6411 and Ti52 titanium alloys,compared to those of marine TC4ELI and Ti80 titanium alloys.Slow strain rate tensile(SSRT)tests were performed to evaluate SCC susceptibility.The SCC susceptibility index(I_(SSRT))was calculated,and the fracture morphologies were investigated to clarify the stress corrosion mechanisms.The experimental results show that the ISSRT of Ti6411 titanium alloy with a lamellar micro structure(LM)is the highest under a strain rate of 1×10^(-6)s^(-1),and the corresponding fracture mode shows a quasi-cleavage fracture with low ductility.TC4ELI alloy with an equiaxed microstructure exhibits excellent SCC resistance.However,the SCC behavior of the Ti80 alloy with a bimodal microstructure is relatively sensitive to high strain rates,and the Ti52 tube with a typical Widmanst?tten microstructure is sensitive to low strain rates.The stress corrosion mechanism can be attributed to the cyclic process of passive film rupture,anodic dissolution,and hydrogen-induced cracking due to a multifactor comprehensive interaction corresponding to specific microstructures,strain rates,and corrosive media.The LM of the Ti6411 plate allowed easy chloride penetration into the bare metal,thereby reducing the protection of the film and resulting in continuous anodic dissolution and hydrogen accumulation at the crack tip.The coupled effect of the internal hydrogen pressure and external tensile stress can easily cause crack propagation and failure under service conditions.
基金financially supported by the National Natural Science Foundation of China(No.52171088).We thank X.Si for assistance in sample preparation.
文摘The strength of traditional Al-Mg alloys primarily depends on cold deformation and increasing Mg content,but it can become susceptible to stress corrosion cracking(SCC)when the Mg content is high(>3 wt.%).Simultaneous optimizing strength and SCC resistance in Al-Mg alloys is challenging.This study introduces a nanostructured Al-10Mg(10 wt.%)alloy with improved strength and SCC resistance by dynamic plastic deformation and optimized annealing.The as-deformed sample exhibits a nano-scaled lamellar structure.With rising annealing temperatures,structure size of the alloy increases while dislocation density decreases,transitioning lamellar to equiaxed grains.Nanostructured Al-10Mg alloys annealed at 250°C exhibit superior mechanical properties and reduced SCC susceptibility at sensitization state.The high fraction of low-angle grain boundaries with a reduction in dislocation density can effectively suppress the nucleation and growth of grain boundary precipitates(GBPs)during sensitization,thereby maintaining a relatively low GBPs coverage.The results provide guidance for designing Al-Mg alloys that are stronger and more resistant to SCC with higher Mg content.
基金Project (2023GK1080) supported by the Major Special Projects of Hunan Province of China。
文摘Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding conditions are insufficient.Here,the stress corrosion cracking(SCC)behavior of base metal(BM)and weld zone(WZ)of TIG welded Al-Mg-Mn-Sc-Zr alloys was investigated by using pre-cracked compact tensile samples immersed in 3.5%NaCl solution.The direct current potential drop(DCPD)method was used to record the crack propagation.The microstructure and fracture morphology of different regions of TIG welded joints were studied by SEM,EBSD and TEM,and the SCC crack propagation mechanism of BM and WZ was analyzed.The results demonstrated that the critical stress intensity factor for stress corrosion cracking(K_(ⅠSCC))of BM and WZ was 7.05 MPa·m_(1/2) and 11.79 MPa·m_(1/2),respectively.Then,the crack propagation rate of BM was faster than that of WZ,and BM was more susceptible to SCC than WZ.Additionally,the fracture mode of the BM mainly exhibited transgranular fracture,while the fracture mode of the WZ mainly exhibited intergranular and transgranular mixed fracture.Moreover,SCC crack propagation was attributed to the combined effect of anodic dissolution and hydrogen embrittlement.This study will provide experimental and theoretical basis for the wide application of TIG welded Al-Mg-Mn-Sc-Zr alloys in aerospace.
基金Projects(2010CB731701,2012CB619502)supported by the National Basic Research Program of ChinaProjects(51201186,51327902)supported by the National Natural Science Foundation of China
文摘The influences of heat treatment on stress corrosion cracking （SCC）, fracture toughness and strength of 7085 aluminum alloy were investigated by slow strain rate testing, Kahn tear testing combined with scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results show that the fracture toughness of T74 overaging is increased by 22.9% at the expense of 13.6% strength, and retrogression and reaging （RRA） enhances fracture toughness 14.2% without reducing the strength compared with T6 temper. The fracture toughness of dual-retrogression and reaging （DRRA） is equivalent to that of T74 with an increased strength of 14.6%. The SCC resistance increases in the order： T6〈RRA〈DRRA≈T74. The differences of fracture toughness and SCC were explained on the basis of the role of matrix precipitates and grain boundary orecioitates.
基金Project(2012CB619505)supported by the National Basic Research Program of ChinaProject(NCET-13-0370)supported by the Program for New Century Excellent Talents in Universities of China
文摘Evolution of microstructure and stress corrosion cracking （SCC） susceptibility of 7050 aluminum alloy with 0.094%, 0.134% and 0.261% Si （mass fraction） in T7651 condition have been investigated. The results show that the area fraction of Mg2Si increases from 0.16% to 1,48% and the size becomes coarser, while the area fraction of the other coarse phases including Al2CuMg, Mg（Al,Cu,Zn）2 and A17Cu2Fe decreases from 2.42% to 0.78% with Si content increasing from 0.094% to 0.261%. The tensile strength and elongation of 7050-T7651 alloys is decreased with the increase of Si content by slow strain rate test （SSRT） in ambient air. However, electrical conductivity is improved and SCC susceptibility is reduced with the increase of Si content by SSRT in corrosion environment with 3.5% NaCl solution.
基金Funded by the National Natural Science Foundation of China (No. 50801066)
文摘The stress corrosion cracking（SCC） behaviour of 7A52 aluminum alloy in air and in 3.5% NaCl solution was researched by slow strain rate test（SSRT） and SEM-EDS. The SCC susceptibility was estimated with the loss of the reduction in area. The experimental results indicate that the SCC susceptibility of 7A52 aluminum alloy in 3.5% chloride solution is the highest at strain rate of 1×10-6 s-1. The lowest one is under the condition of 1×10-5 s-1. Stress concentration and anode dissolving around Al-Fe-Mn intermetallics initiate micropores which will result in microcracks. The existence of intermetallics in the microstructure may play an important role in understanding the SCC initiation mechanisms of 7A52 aluminum alloy.
文摘Stress corrosion cracking （SCC） is degradation of mechanical properties under the combined action of stress and corrosive environment of the susceptible material. Out of eight series of aluminium alloys, 2xxx, 5xxx and 7xxx aluminium alloys are susceptible to SCC. Among them, 7xxx series aluminium alloys have specific application in aerospace, military and structural industries due to superior mechanical properties. In these high strength 7xxx aluminium alloys, SCC plays a vital factor of consideration, as these failures are catastrophic during the service. The understanding of SCC behaviour possesses critical challenge for this alloy. The main aim of this review paper is to understand the effect of constituent alloying elements on the response of microstructural variation in various heat-treated conditions on SCC behavior. Further, review was made for improving the SCC resistance using thermomechanical treatments and by surface modifications of 7xxx alloys. Apart from a brief review on SCC of 7xxx alloys, this paper presents the effect of stress and pre-strain, effect of constituent alloying elements in the alloy, and the effect of environments on SCC behaviour. In addition, the SCC behaviours of weldments, 7xxx metal matrix composites and also laser surface modifications were also reviewed.
基金supported by the National Science & Technology Infrastructure Development Program of China(No.2005DKA10400)
文摘Hydrogen was a key factor resulting in stress corrosion cracking （SCC） of X80 pipeline steel in Ku＇erle soil simulated solution. In this article, the effect of hydrogen on the SCC susceptibility of X80 steel was investigated further by slow strain rate tensile test, the surface fractures were observed using scanning electron microscopy （SEM）, and the fracture mechanism of SCC was discussed. The results indicate that hydrogen increases the SCC susceptibility. The SEM micrographs of hydrogen precharged samples presents a brittle quasi-cleavage feature, and pits facilitate the transgranular crack initiation. In the electrochemical impedance spectroscopy （EIS） measurement, the decreased polarization resistance and the pitting resistance of samples with hydrogen indicate that hydrogen increases the dissolution rate and deteriorates the pitting corrosion resistance. The potentiodynamic polarization curves present that hydrogen also accelerates the dissolution rate of the crack tip.
基金supported by the State’s Key Project of Research and Development (Grant Nos. 2016YFB1200600, and 2016YFB1200504)the Strategic Priority Program of the Chinese Academy of Sciences (Grant No. XDB22000000)
文摘Influence of Sc content on microstructure and stress corrosion cracking behavior of medium strength AI-Zn-Mg alloy have been investigated by optical microscopy, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and slow strain rate test. The results indicate that the addition of Sc results in the formation of the quaternary coherent AI3（Sc, Zr, Ti） dispersoids during homogenization treatment, which will inhibit the dynamic recrystallization behavior. The number density ofAl3（Sc, Zr, Ti） particles increases with the increase of Sc content, and thus the recrystallization fraction of hot-extruded alloy is reduced and the peak strength in two-stage artificial aging sample is enhanced. At the same time, the wide of precipitation free zone is reduced, and the content of Zn and Mg in grain boundary particles and precipitation free zone is increased with the increase of Sc content. In peak-aged state, the 0.06 wt% Sc added alloy shows the better stress corrosion cracking resistance than the Sc-free alloy because of the reduction of recrystallization fraction and the interrupted distribution of grain boundary precipitates along grain boundary. However, the further addition of Sc to 0.11 wt% will result in the deterioration of stress corrosion cracking resistance due to the increase of electrochemical activity of grain boundary particles and precipitation free zone as well as hydrogen embrittlement.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
基金financial support and Program of the Ministry of Education in China (2011)。
文摘5083 Al alloy sheets with different grain sizes(8.7-79.2 μm) were obtained by cold rolling and annealing. Their microstructures, intergranular corrosion(IGC), stress corrosion cracking(SCC), and crack propagation behaviors were investigated. The results showed that samples with coarse grains exhibit better IGC resistance with a corrosion depth of 15 μm. The slow strain rate test results revealed that fine-grained samples exhibit better SCC resistance with a susceptibility index(ISSRT) of 11.2%. Furthermore, based on the crack propagation mechanism, grain refinement can improve the SCC resistance by increasing the number of grain boundaries to induce the corrosion crack propagation along a tortuous path. The grains with {011} orientation could hinder crack propagation by orientating it toward the low-angle grain boundary region. The crack in the fine-grained material slowly propagates due to the tortuous path, and low H;and Cl;concentrations.
基金Projects (2010CB731701, 2012CB619502) supported by National Basic Research Program of ChinaProject (51021063) supported by the Creative Research Group of National Natural Science Foundation of China
文摘The influence of quenching rate on microstructure and stress corrosion cracking （SCC） of 7085 aluminum alloy was investigated by tensile test, slow strain rate test （SSRT）, combined with scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and electrochemical test. The results show that with decreasing the quenching rate, the size and inter-particle distance of the grain boundary precipitates as well as precipitation free zone width increase, but the copper content of grain boundary precipitates decreases. The SCC resistance of the samples increases first and then decreases, which is attributed to the copper content, size and distribution of grain boundary precipitates.
基金financial supports by National Key R&D Program of China (No. 2016YFB1200600 and No. 2016YFB1200504)Strategic Priority Program of the Chinese Academy of Sciences (No. XDB22000000)
文摘Different artificial two-stage ageing behaviors and their effect on stress corrosion cracking （SCC） susceptibility of AI-Zn-Mg alloy have been investigated. The experimental results show that two hardness peaks present on the second-stage ageing-hardening curve when the first-stage ageing is dealt with comparatively lower temperature than the conventional one. The first peak is caused by dispersive and evenly distributed G.P. zones, while η ′phases and coarsened G.P. zones contribute to the second peak. Tensile strength of experimental alloy raises 9.6% （33.2 MPa） and SCC susceptibility decreases 38.9% by applying the second peak ageing regime instead of conventional T73. AI-Zn-Mg alloy obtains high strength and SCC resistance due to its finely dispersive matrix precipitates （MPts）, coarsened and discontinuous grain boundary precipitates （GBPs）, as well as the narrow precipitate free zone （PFZ） in the second peak ageing condition. 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
基金financial supports from the National Key Research and Development Program of China(No.2016-YFB0300801)the State Key Laboratory of High Performance Complex Manufacturing of Central South University,China(No.ZZYJKT2020-03)the National Key Laboratory of Science and Technology for National Defence on High-strength Lightweight Structural Materials of China(No.20190104)。
文摘The correlations among the corrosion behaviour,grain-boundary microchemistry,and Zn content in Al-Zn-Mg-Cu alloys were studied using stress corrosion cracking(SCC)and intergranular corrosion(IGC)tests,combined with scanning electron microscopy(SEM)and high-angle angular dark field scanning transmission electron microscopy(HAADF-STEM)microstructural examinations.The results showed that the tensile strength enhancement of high Zn-containing Al-Zn-Mg-Cu alloys was mainly attributed to the high density nano-scale matrix precipitates.The SCC plateau velocity for the alloy with 11.0 wt.%Zn was about an order of magnitude greater than that of the alloy with 7.9 wt.%Zn,which was mainly associated with Zn enrichment in grain boundary precipitates and wide precipitates-free zones.The SCC mechanisms of different Zn-containing alloys were discussed based on fracture features,grain-boundary microchemistry,and electrochemical properties.
基金financially supported by the State Key Fundamental Research Program of China (No. 2005CB623706)
文摘The effects of pre-deformation and strain rate on the stress corrosion cracking （SCC） behavior of aluminum alloy 2519 in air and in 3.5% NaCI water solution were investigated by means of slow strain rate tension （SSRT）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results indicate that the alloy is susceptible to SCC in 3.5% NaCI water solution and not in air. At the same pre-deformation, the alloy is more susceptible to SCC at 1.33 × 10^-5 s^-1 than at 6.66 × 10^-5 s^-1. Moreover, it is more susceptible to SCC at free pre-deformation than at 10% pre-deformation at the same strain rate. The number of 0 precipitated along the grain boundaries is reduced and distributed discontinuously, at the same time, the precipitate-free zones （PFZ） become narrow and the susceptibility to stress corrosion cracking is reduced after 10% pre-deformation.
基金supported by the National Natural Science Foundation of China (Grant No. 51025104)
文摘Constant load tests in NS4 solution purged with N2-5%CO2 gas mixture were conducted on American Petroleum Institute （API） X80 pipeline steel applied in the 2nd West-East （;as Pipeline project with and without preload. The results show that cracks could initiate and propagate in X80 pipeline steel in near-neutral pH environment under a constant load condition. The life of crack initiation and propagation increased with decreasing applied stress. Preload did not change its corrosion behavior obviously. However, preload reduced the time for crack initiation.
