Experiments were conducted to study the general room temperature corrosion characteristics of heat-treated and non-heat-treated Al-Li alloys with different Li compositions. Corrosion rate was measured using both the p...Experiments were conducted to study the general room temperature corrosion characteristics of heat-treated and non-heat-treated Al-Li alloys with different Li compositions. Corrosion rate was measured using both the polarisation method and the weight-loss method. It was observed that the samples with higher Li content had lower corrosion resistance than those with lower Li content. Moreover, for all the specimens tested, it was fOund that heat treatment at 180℃ for 2 h (for the purpose of precipitation hardening) severely reduced the corrosion resistance,whereas heat treatment at 180℃ for 6 h significantly increased the corrosion resistance.展开更多
This paper presents a model of fatigue crack growth in a welded joint and a two-dimensional model of anodic dissolution based on Donahue model and anodic dissolution mechanism,respectively.In addition,a model for pred...This paper presents a model of fatigue crack growth in a welded joint and a two-dimensional model of anodic dissolution based on Donahue model and anodic dissolution mechanism,respectively.In addition,a model for predicting the corrosion fatigue crack growth rate in welded joints of steel marine structures is established and crack growth mechanisms are analyzed.The results show that during early stages of crack growth,corrosion fatigue crack growth rate in welded joints is mainly controlled by corrosion action,whereas cyclic loading becomes more influential during the later stage of crack propagation.Loading frequency and effective stress ratio can affect rupture period of protective film at the corrosion fatigue crack tip and the length of corrosion crack increment,respectively,which changes the influence of corrosion action on crack growth rate.However,the impact of stress amplitude on crack growth rate is only significant when crack propagation is caused by cyclic loading.Welding residual stress not only improves the effective stress ratio of cyclic loading,but also promotes crack closure and increases corrosion fatigue crack growth rate in welded joints.Compared to corrosion action,welding residual stress has a more significant influence on crack growth caused by cyclic loading.展开更多
The optimum corrosion protection potentials were examined for 5052-O Al alloy,which is mainly used in ships.Various electrochemical experiments were carried out and the surface morphologies of specimens were observed ...The optimum corrosion protection potentials were examined for 5052-O Al alloy,which is mainly used in ships.Various electrochemical experiments were carried out and the surface morphologies of specimens were observed by scanning electron microscopy（SEM） in order to determine the optimum corrosion protection potential to overcome pitting,corrosion,stress corrosion cracking（SCC）,and hydrogen embrittlement in sea water.An optimum protection potential range of-1.3 V to-0.7 V was determined under the application of an impressed current cathodic protection（ICCP） system.The low current densities were shown in the range of-1.3 V to-0.7 V in the electrochemical experiments and good specimen surface morphologies were observed after potentiostatic experiment.展开更多
Among Al alloys,particularly 5000 series Al Mg and 6000 series Al Mg Si often used as marine materials have excellent corrosion resistance,low melting point,and thereby showing recycling availability when compared to ...Among Al alloys,particularly 5000 series Al Mg and 6000 series Al Mg Si often used as marine materials have excellent corrosion resistance,low melting point,and thereby showing recycling availability when compared to other metals.Variety experiments were conducted to select the most suitable material for marine environments.All electrochemical experiments were conducted in natural seawater.The corrosion test was performed in many methods such as anodic/cathodic polarization and Tafel analysis using multi-channel potentio/galvanostat WMPG 1000.As results,anodic and cathodic polarization behaviors indicate the characteristics of passive state and concentration polarization by reduction reaction in dissolved oxygen,which shows excellent electrochemical behaviors.Tafel analysis results show no significant difference but 5052-O alloy of various alloy materials indicates the lowest corrosion current density.Therefore,5052-O Al alloy presents most anti-corrosion material in marine environment.展开更多
To investigate the effect of grain refinement on the material properties of recently developed Al-25 Zn-3 Cu based alloys,Al-25 Zn-3 Cu,Al-25 Zn-3 Cu-0.01 Ti,Al-25 Zn-3 Cu-3 Si and Al-25 Zn-3 Cu-3 Si-0.01 Ti alloys we...To investigate the effect of grain refinement on the material properties of recently developed Al-25 Zn-3 Cu based alloys,Al-25 Zn-3 Cu,Al-25 Zn-3 Cu-0.01 Ti,Al-25 Zn-3 Cu-3 Si and Al-25 Zn-3 Cu-3 Si-0.01 Ti alloys were produced by permanent mold casting method.Microstructures of the alloys were examined by SEM.Hardness and mechanical properties of the alloys were determined by Brinell method and tensile tests,respectively.Tribological characteristics of the alloys were investigated by a ball-on-disc type test machine.Corrosion properties of the alloys were examined by an electrochemical corrosion experimental setup.It was observed that microstructure of the ternary A1-25 Zn-3 Cu alloy consisted ofα,α+ηandθ(Al2Cu)phases.It was also observed that the addition of 3 wt.%Si to A1-25Zn-3Cu alloy resulted in the formation of silicon particles in its microstructure.The addition of 0.01 wt.%Ti to the Al-25Zn-3Cu and Al-25 Zn-3 Cu-3 Si alloys caused a decrement in grain size by approximately 20%and 39%and an increment in hardness from HRB 130 to 137 and from HRB 141 to 156,respectively.Yield strengths of these alloys increased from 278 to 297 MPa and from 320 to 336 MPa while their tensile strengths increased from 317 to 340 MPa and from 334 to 352 MPa.Wear resistance of the alloys increased,but corrosion resistance decreased with titanium addition.展开更多
In the present study,the thermal,mechanical,and biological properties of xAg/Ti-30Ta(x=0,0.41,0.82 and 2.48 at%)shape memory alloys(SMAs)were investigated.The study was conducted using optical and scanning electron mi...In the present study,the thermal,mechanical,and biological properties of xAg/Ti-30Ta(x=0,0.41,0.82 and 2.48 at%)shape memory alloys(SMAs)were investigated.The study was conducted using optical and scanning electron microscopy(SEM),X-ray diffractometry(XRD),compression test,and shape memory testing.The xAg/Ti-Ta was made using a powder metallurgy technique and microwave-sintering process.The results revealed that the addition of Ag has a significant effect on the pore size and shape,whereas the smallest pore size of 11μm was found with the addition of 0.41 at%along with a relative density of 72%.The fracture stress and strain increased with the addition of Ag,reaching the minimum values around 0.41 at%Ag.Therefore,this composition showed the maximum stress and strain at fracture region.Moreover,0.82 Ag/Ti-Ta shows more excellent corrosion resistance and biocompatibility than other percentages,obtaining almost the same behaviour of the pure Ti and Ti-6Al-4V alloys,which can be recommended for their promising and potential response for biomaterial applications.展开更多
The impact corrosion-abrasion properties and mechanism of high manganese steel were investigated under different impact energies. The result shows that the wearability of the steel decreases with the increase of the i...The impact corrosion-abrasion properties and mechanism of high manganese steel were investigated under different impact energies. The result shows that the wearability of the steel decreases with the increase of the impact energy. The dominant failure mechanism at a lower impact energy is the rupture of extrusion edge along root and a slight shallow-layer spalling. It transforms to shallow-layer fatigue flaking along with serious corrosion-abrasion when the impact energy is increased, and finally changes to bulk flaking of hardened laver caused by deeo work-hardening and heaw corrosion-abrasion.展开更多
The feasibility of applying the grain boundary character distribution(GBCD)optimization to Inconel 625 for improving the intergranular corrosion(IGC)resistance was studied.The GBCD was obtained and characterized by el...The feasibility of applying the grain boundary character distribution(GBCD)optimization to Inconel 625 for improving the intergranular corrosion(IGC)resistance was studied.The GBCD was obtained and characterized by electron backscatter diffraction(EBSD)analysis,and its optimization was mainly attributed to annealing twins(Σ3)and twins related to boundaries formed during thermal-mechanical processing(TMP).Through TMP of 5%cold rolling and subsequent annealing at 1150℃for 5 min,the proportion of lowΣcoincidence site lattice(CSL)grain boundaries of the Inconel 625 can be enhanced to about 35.8%which mainly were ofΣ3^(n)(n=1,2,3)type.There is an increase of 24.8%compared with the solution-treated sample,and simultaneously the large-size highly-twinned grain-cluster microstructure is formed.The grain-cluster is mainly composed ofΣ3-Σ3-Σ9 orΣ3-Σ9-Σ27 triple junctions,which is mainly caused by boundary reactions during grain growth.Among them,the IGC resistance ofΣ3 grain boundaries,Σ9 grain boundaries and random grain boundaries is sequentially weakened.With the increase of the lowΣCSL grain boundary fraction,the IGC resistance of Inconel 625 improves.The essential reason is the amount ofΣ3 boundaries interrupting the random boundary network increases and the large grain-cluster arrests the penetration of IGC.展开更多
Sheets of aluminum 6061 alloy were welded using bypass-current double-sided arc welding with Al-Si filler wire to investigate the effect of Al-Si intermetallic compounds on the microstructure, microhardness and corros...Sheets of aluminum 6061 alloy were welded using bypass-current double-sided arc welding with Al-Si filler wire to investigate the effect of Al-Si intermetallic compounds on the microstructure, microhardness and corrosion behavior of weld joint. Experimental results indicated that the Al4.5FeSi phase in the topside of the weld joint was finer than that in the backside and newly formed phase of Al0.5Fe3Si0.5 was observed in the backside. The formation of reinforcing phases of Al-Fe-Si in the weld improved the microhardness of the weld by about 18%. The corrosion resistance of the weld zone was greater than that of the base metal, while the corrosion current displayed opposite, and the corrosion resistance of the weld region was better than that of the base metal.展开更多
To solve the problem of corrosion acoustic emission （AE） source feature extraction and recognition, the AE detection validation and the amplitude-frequency characteristics were derived in theory. The amplitude of AE...To solve the problem of corrosion acoustic emission （AE） source feature extraction and recognition, the AE detection validation and the amplitude-frequency characteristics were derived in theory. The amplitude of AE signal generated by bubble burst is proportional to its radius square and the liquid level, while the AE signal frequency is inversely proportional to the bubble radius. The AE signal amplitude of the steel and the steel corrosion product cracking is proportional to the local stress, and the AE signal frequency is proportional to the crack propagation velocity and inversely proportional to the crack propagation distance. Three Q235 specimens were separately immersed in the solution of 10% FeC13.6H20, 5% CuSOa.5H20 and 10% FeC13.6H20 with 0.01 mol/L HCL. The AE systems with high frequency and low frequency were used to detect the whole corrosion process AE signals. The AE signals of Q235 steel and the steel corrosion products cracking were detected as the verification experiment. The AE signals from different sources could be distinguished by AE hits count and the power spectrum. It is coincident with theoretical analysis. These conclusions have significant guidance for the corrosion detection and evaluation by on-line acoustic emission detecting.展开更多
The corrosion behavior of high-strength low-alloy 921A steel in a simulated marine atmospheric environment was studied using a high-throughput experimental method.The corrosion behavior,corrosion morphology,and corros...The corrosion behavior of high-strength low-alloy 921A steel in a simulated marine atmospheric environment was studied using a high-throughput experimental method.The corrosion behavior,corrosion morphology,and corrosion products of 921A steels were analyzed using various techniques,including corrosion mass loss method,polarization curve,white-light interferometry,scanning electron microscopy,energy-dispersive spectrometry,microbeam X-ray fluorescence spectrometry,X-ray diffraction technique,and X-ray photoelectron spectroscopy.The test results indicated that 921A steel exhibits better corrosion resistance than Q450NQR1 steel in simulated harsh atmospheric environments,as evidenced by a lower corrosion mass loss rate throughout the corrosion tests.The corrosion products of both steels consisted ofα-FeOOH,Fe_(3)O_(4),andγ-FeOOH,withα-FeOOH being more prevalent in the rust layer of 921A steel than in Q450NQR1 steel.The inner rust layer of 921A steel also exhibited an appositional enrichment region of Cr,Ni,Mo,and V,leading to its superior corrosion resistance compared to that of Q450NQR1 steel.The efficacy of high-throughput accelerated corrosion experimental methods was highlighted for evaluating the corrosion resistance of steel materials in harsh environmental conditions.The findings suggest that 921A steel exhibits better corrosion resistance compared to Q450NQR1 steel and has the potential to be more suitable in harsh marine atmospheric environments.The characterization of the rust layer structures and composition reveals the parallel enrichment of certain elements in the inner rust layer of 921A steel,which enhances its corrosion resistance.展开更多
文摘Experiments were conducted to study the general room temperature corrosion characteristics of heat-treated and non-heat-treated Al-Li alloys with different Li compositions. Corrosion rate was measured using both the polarisation method and the weight-loss method. It was observed that the samples with higher Li content had lower corrosion resistance than those with lower Li content. Moreover, for all the specimens tested, it was fOund that heat treatment at 180℃ for 2 h (for the purpose of precipitation hardening) severely reduced the corrosion resistance,whereas heat treatment at 180℃ for 6 h significantly increased the corrosion resistance.
基金Project(2018M643852)supported by the Postdoctoral Science Foundation of ChinaProjects(30110010403,30110030103)supported by Equipment Pre-Research Project,ChinaProject(51979280)supported by the National Natural Science Foundation of China。
文摘This paper presents a model of fatigue crack growth in a welded joint and a two-dimensional model of anodic dissolution based on Donahue model and anodic dissolution mechanism,respectively.In addition,a model for predicting the corrosion fatigue crack growth rate in welded joints of steel marine structures is established and crack growth mechanisms are analyzed.The results show that during early stages of crack growth,corrosion fatigue crack growth rate in welded joints is mainly controlled by corrosion action,whereas cyclic loading becomes more influential during the later stage of crack propagation.Loading frequency and effective stress ratio can affect rupture period of protective film at the corrosion fatigue crack tip and the length of corrosion crack increment,respectively,which changes the influence of corrosion action on crack growth rate.However,the impact of stress amplitude on crack growth rate is only significant when crack propagation is caused by cyclic loading.Welding residual stress not only improves the effective stress ratio of cyclic loading,but also promotes crack closure and increases corrosion fatigue crack growth rate in welded joints.Compared to corrosion action,welding residual stress has a more significant influence on crack growth caused by cyclic loading.
文摘The optimum corrosion protection potentials were examined for 5052-O Al alloy,which is mainly used in ships.Various electrochemical experiments were carried out and the surface morphologies of specimens were observed by scanning electron microscopy（SEM） in order to determine the optimum corrosion protection potential to overcome pitting,corrosion,stress corrosion cracking（SCC）,and hydrogen embrittlement in sea water.An optimum protection potential range of-1.3 V to-0.7 V was determined under the application of an impressed current cathodic protection（ICCP） system.The low current densities were shown in the range of-1.3 V to-0.7 V in the electrochemical experiments and good specimen surface morphologies were observed after potentiostatic experiment.
基金Project supported by the Cooperative Promotion Center of Science & Technology of JEONNAM TECHNOPARKMinistry of Education,Science and Technology(MEST)through"The research & development support of JEONNAM southwest science park"
文摘Among Al alloys,particularly 5000 series Al Mg and 6000 series Al Mg Si often used as marine materials have excellent corrosion resistance,low melting point,and thereby showing recycling availability when compared to other metals.Variety experiments were conducted to select the most suitable material for marine environments.All electrochemical experiments were conducted in natural seawater.The corrosion test was performed in many methods such as anodic/cathodic polarization and Tafel analysis using multi-channel potentio/galvanostat WMPG 1000.As results,anodic and cathodic polarization behaviors indicate the characteristics of passive state and concentration polarization by reduction reaction in dissolved oxygen,which shows excellent electrochemical behaviors.Tafel analysis results show no significant difference but 5052-O alloy of various alloy materials indicates the lowest corrosion current density.Therefore,5052-O Al alloy presents most anti-corrosion material in marine environment.
文摘To investigate the effect of grain refinement on the material properties of recently developed Al-25 Zn-3 Cu based alloys,Al-25 Zn-3 Cu,Al-25 Zn-3 Cu-0.01 Ti,Al-25 Zn-3 Cu-3 Si and Al-25 Zn-3 Cu-3 Si-0.01 Ti alloys were produced by permanent mold casting method.Microstructures of the alloys were examined by SEM.Hardness and mechanical properties of the alloys were determined by Brinell method and tensile tests,respectively.Tribological characteristics of the alloys were investigated by a ball-on-disc type test machine.Corrosion properties of the alloys were examined by an electrochemical corrosion experimental setup.It was observed that microstructure of the ternary A1-25 Zn-3 Cu alloy consisted ofα,α+ηandθ(Al2Cu)phases.It was also observed that the addition of 3 wt.%Si to A1-25Zn-3Cu alloy resulted in the formation of silicon particles in its microstructure.The addition of 0.01 wt.%Ti to the Al-25Zn-3Cu and Al-25 Zn-3 Cu-3 Si alloys caused a decrement in grain size by approximately 20%and 39%and an increment in hardness from HRB 130 to 137 and from HRB 141 to 156,respectively.Yield strengths of these alloys increased from 278 to 297 MPa and from 320 to 336 MPa while their tensile strengths increased from 317 to 340 MPa and from 334 to 352 MPa.Wear resistance of the alloys increased,but corrosion resistance decreased with titanium addition.
基金Project(Q.J130000.2524.12H60)supported by the Ministry of Higher Education of Malaysia and Universiti Teknologi Malaysia。
文摘In the present study,the thermal,mechanical,and biological properties of xAg/Ti-30Ta(x=0,0.41,0.82 and 2.48 at%)shape memory alloys(SMAs)were investigated.The study was conducted using optical and scanning electron microscopy(SEM),X-ray diffractometry(XRD),compression test,and shape memory testing.The xAg/Ti-Ta was made using a powder metallurgy technique and microwave-sintering process.The results revealed that the addition of Ag has a significant effect on the pore size and shape,whereas the smallest pore size of 11μm was found with the addition of 0.41 at%along with a relative density of 72%.The fracture stress and strain increased with the addition of Ag,reaching the minimum values around 0.41 at%Ag.Therefore,this composition showed the maximum stress and strain at fracture region.Moreover,0.82 Ag/Ti-Ta shows more excellent corrosion resistance and biocompatibility than other percentages,obtaining almost the same behaviour of the pure Ti and Ti-6Al-4V alloys,which can be recommended for their promising and potential response for biomaterial applications.
基金the Doctoral Authorization Point Foundation of Education Ministry of China(No.20040359004)the Major Project Foundation of Education Office of Anhui Province(No.KJ2007A060)
文摘The impact corrosion-abrasion properties and mechanism of high manganese steel were investigated under different impact energies. The result shows that the wearability of the steel decreases with the increase of the impact energy. The dominant failure mechanism at a lower impact energy is the rupture of extrusion edge along root and a slight shallow-layer spalling. It transforms to shallow-layer fatigue flaking along with serious corrosion-abrasion when the impact energy is increased, and finally changes to bulk flaking of hardened laver caused by deeo work-hardening and heaw corrosion-abrasion.
基金Funded in part by the National Key Research and Development Program of China(No.2017YFA07007003)the National Natural Science Foundation of China(No.51661019)+1 种基金the Major Projects of Science and Technology in Gansu Province(No.145RTSA004)the Hongliu First-class Discipline Construction Plan of Lanzhou University of Technology。
文摘The feasibility of applying the grain boundary character distribution(GBCD)optimization to Inconel 625 for improving the intergranular corrosion(IGC)resistance was studied.The GBCD was obtained and characterized by electron backscatter diffraction(EBSD)analysis,and its optimization was mainly attributed to annealing twins(Σ3)and twins related to boundaries formed during thermal-mechanical processing(TMP).Through TMP of 5%cold rolling and subsequent annealing at 1150℃for 5 min,the proportion of lowΣcoincidence site lattice(CSL)grain boundaries of the Inconel 625 can be enhanced to about 35.8%which mainly were ofΣ3^(n)(n=1,2,3)type.There is an increase of 24.8%compared with the solution-treated sample,and simultaneously the large-size highly-twinned grain-cluster microstructure is formed.The grain-cluster is mainly composed ofΣ3-Σ3-Σ9 orΣ3-Σ9-Σ27 triple junctions,which is mainly caused by boundary reactions during grain growth.Among them,the IGC resistance ofΣ3 grain boundaries,Σ9 grain boundaries and random grain boundaries is sequentially weakened.With the increase of the lowΣCSL grain boundary fraction,the IGC resistance of Inconel 625 improves.The essential reason is the amount ofΣ3 boundaries interrupting the random boundary network increases and the large grain-cluster arrests the penetration of IGC.
基金financially supported by the National Natural Science Foundation of China(No.51005049)
文摘Sheets of aluminum 6061 alloy were welded using bypass-current double-sided arc welding with Al-Si filler wire to investigate the effect of Al-Si intermetallic compounds on the microstructure, microhardness and corrosion behavior of weld joint. Experimental results indicated that the Al4.5FeSi phase in the topside of the weld joint was finer than that in the backside and newly formed phase of Al0.5Fe3Si0.5 was observed in the backside. The formation of reinforcing phases of Al-Fe-Si in the weld improved the microhardness of the weld by about 18%. The corrosion resistance of the weld zone was greater than that of the base metal, while the corrosion current displayed opposite, and the corrosion resistance of the weld region was better than that of the base metal.
基金supported by the Innovation Team Project of Liaoning Provincial Education Department(LT2010082)
文摘To solve the problem of corrosion acoustic emission （AE） source feature extraction and recognition, the AE detection validation and the amplitude-frequency characteristics were derived in theory. The amplitude of AE signal generated by bubble burst is proportional to its radius square and the liquid level, while the AE signal frequency is inversely proportional to the bubble radius. The AE signal amplitude of the steel and the steel corrosion product cracking is proportional to the local stress, and the AE signal frequency is proportional to the crack propagation velocity and inversely proportional to the crack propagation distance. Three Q235 specimens were separately immersed in the solution of 10% FeC13.6H20, 5% CuSOa.5H20 and 10% FeC13.6H20 with 0.01 mol/L HCL. The AE systems with high frequency and low frequency were used to detect the whole corrosion process AE signals. The AE signals of Q235 steel and the steel corrosion products cracking were detected as the verification experiment. The AE signals from different sources could be distinguished by AE hits count and the power spectrum. It is coincident with theoretical analysis. These conclusions have significant guidance for the corrosion detection and evaluation by on-line acoustic emission detecting.
基金the National Key Research and Development Program of China(Grant No.2021YFB3702103).
文摘The corrosion behavior of high-strength low-alloy 921A steel in a simulated marine atmospheric environment was studied using a high-throughput experimental method.The corrosion behavior,corrosion morphology,and corrosion products of 921A steels were analyzed using various techniques,including corrosion mass loss method,polarization curve,white-light interferometry,scanning electron microscopy,energy-dispersive spectrometry,microbeam X-ray fluorescence spectrometry,X-ray diffraction technique,and X-ray photoelectron spectroscopy.The test results indicated that 921A steel exhibits better corrosion resistance than Q450NQR1 steel in simulated harsh atmospheric environments,as evidenced by a lower corrosion mass loss rate throughout the corrosion tests.The corrosion products of both steels consisted ofα-FeOOH,Fe_(3)O_(4),andγ-FeOOH,withα-FeOOH being more prevalent in the rust layer of 921A steel than in Q450NQR1 steel.The inner rust layer of 921A steel also exhibited an appositional enrichment region of Cr,Ni,Mo,and V,leading to its superior corrosion resistance compared to that of Q450NQR1 steel.The efficacy of high-throughput accelerated corrosion experimental methods was highlighted for evaluating the corrosion resistance of steel materials in harsh environmental conditions.The findings suggest that 921A steel exhibits better corrosion resistance compared to Q450NQR1 steel and has the potential to be more suitable in harsh marine atmospheric environments.The characterization of the rust layer structures and composition reveals the parallel enrichment of certain elements in the inner rust layer of 921A steel,which enhances its corrosion resistance.
