Effect of the second phase in the micro-galvanic corrosion of a commercial Mg alloy containing rare earth elements, cast WE43 alloy,was investigated in 0.6 M NaCl solution and 0.6 M Na_(2)SO_(4)solution by scanning el...Effect of the second phase in the micro-galvanic corrosion of a commercial Mg alloy containing rare earth elements, cast WE43 alloy,was investigated in 0.6 M NaCl solution and 0.6 M Na_(2)SO_(4)solution by scanning electron microscopy(SEM) observations, scanning Kelvin probe force microscopy(SKPFM) analysis, hydrogen evolution, weight loss measurement, and electrochemical techniques. It is confirmed that the second phase of cast WE43 alloy is more active than Mg matrix and exhibits an anodic role in the micro-galvanic corrosion with α-Mg matrix as cathode and dissolves preferentially in Na_(2)SO_(4)solution, in contrast to the situation in NaCl solution. The corrosion rate of cast WE43 alloy in Na_(2)SO_(4)solution is much higher than that in NaCl solution, which is different from the conventional wisdom and could be attributed to the different role of the second phase in the micro-galvanic corrosion in two solutions.展开更多
The corrosion behavior of the as-received steel and the spheroidized steel in acidic chloride environment was investigated. The results indicate the corrosion mode and corrosion rate of two steels are diverse due to t...The corrosion behavior of the as-received steel and the spheroidized steel in acidic chloride environment was investigated. The results indicate the corrosion mode and corrosion rate of two steels are diverse due to their difference in microstructure. For as-received steel with ferrite-pearlite microstructure, severe localized corrosion happens on the pearlite regions, and plenty of cathodic cementite remains in the pits, further strengthening the micro-galvanic effect and accelerating the corrosion rate. While for spheroidized steel with tempered martensite microstructure, the nanosized cementite particles evenly distributed on the ferrite substrate are easy to fall off, which can significantly reduce the cementite accumulation on the steel surface, relieving the acceleration effect of micro-galvanic corrosion.展开更多
A model specimen with a single boundary of theα/βphase simulating Mg-Al alloys was successfully fabricated by spark plasma sintering.A small electrode area ofαphase orβphase was prepared using the model specimen,a...A model specimen with a single boundary of theα/βphase simulating Mg-Al alloys was successfully fabricated by spark plasma sintering.A small electrode area ofαphase orβphase was prepared using the model specimen,and the OCPs(open-circuit potentials)of each phase and a small electrode area containing theα/βphase boundary in 0.1 M NaCl at pH 8.0 were compared:theβphase exhibited a higher potential,and theαphase showed a lower potential.The OCP of the small area containing theα/βphase boundary was the intermediate value of these phases.In a small area containingα/βphase boundary,discoloration and gas bubbles were observed on theαphase,but no bubble generation was detected on theβphase.The gas bubbles were initially generated on theαphase near theβphase,but as the discoloration(corrosion)of theαphase approached theβphase,the bubbles were generated on theβphase.In micro-galvanic corrosion of theαandβphases,theβphase did not always function as the preferred cathode.Theαphase partially corroded(or discolored)and became the anodes,so that the surrounding areas were most likely to be the cathodes.When corroded areas(anodes)in theαphase approached theβphase,theβphase would become cathodes.In addition to the micro-galvanic corrosion mechanism,the role of Al in corrosion resistance at theα/βphase boundary was determined by surface analysis.展开更多
The localized micro-galvanic corrosion process and the kinetic information of Mg-(7,9)Al-1Fe-x Nd alloys were investigated by in situ observation under electrochemical control and in situ atomic force microscopy(AFM)i...The localized micro-galvanic corrosion process and the kinetic information of Mg-(7,9)Al-1Fe-x Nd alloys were investigated by in situ observation under electrochemical control and in situ atomic force microscopy(AFM)in an electrolyte environment.The results revealed that the formation of the Nd-rich phase in alloys resulted in a decrease in the Volta potential difference from~400 m V(AlFe3/α-Mg)to~220 mV(Nd-rich/α-Mg),reducing the corrosion products around the cathodic phase and corrosion current density of the microscale area.The addition of Nd significantly improved the corrosion resistance,mainly due to the suppression of the micro-galvanic corrosion between the second phases and substrate.Finally,the corrosion mechanism of Mg-(7,9)Al-1Fe-x Nd alloys was discussed based on in situ observations and electrochemical results.展开更多
The phosphate protective film and micro-galvanic corrosion of biological Mg-3Zn-xNd (x = 0, 0.6, 1.2) alloys were investigated by scanning and transmission electron microscopy, quasi-in-situ observation, scanning Kelv...The phosphate protective film and micro-galvanic corrosion of biological Mg-3Zn-xNd (x = 0, 0.6, 1.2) alloys were investigated by scanning and transmission electron microscopy, quasi-in-situ observation, scanning Kelvin probe force microscopy (SKPFM) and electrochemical tests. The results revealed the Mg-Zn-Nd phases formed in Mg-3Zn alloy contained with Nd. Adding Nd resulted in a significant decline in the cracks of the phosphate protective film and micro-galvanic corrosion of alloys, which were recorded by quasi-in-situ observation. In addition, the Volta potential difference of Mg-Zn-Nd/α-Mg (~ 188 mV) was lower than MgZn/α-Mg (~ 419 mV) and Zn-rich/α-Mg (~ 260 mV), and the corrosion rates of alloys markedly decreased after the addition of 0.6 wt% Nd. The improvement in corrosion resistance of Nd-containing alloys was mainly attributed to the following: (i) the addition of Nd reduced the Volta potential difference (second phases/α-Mg);(ii) the phosphate protective film containing Nd_(2)O_(3) deposited on the surface of the alloys, effectively preventing the penetration of harmful anions.展开更多
In response to the interest in degradable magnesium staples for oral and maxillofacial surgical procedures,high-performance Mg−3Zn−0.2Ca−2Ag alloy wires were reported.The impact of annealing temperature on the mechani...In response to the interest in degradable magnesium staples for oral and maxillofacial surgical procedures,high-performance Mg−3Zn−0.2Ca−2Ag alloy wires were reported.The impact of annealing temperature on the mechanical properties and corrosion behavior of the alloy wires was investigated.Results indicated that an increased annealing temperature led to grain growth,reduced the volume fraction of the second phase,and lowered dislocation density,causing decreased strength.The alloy annealed at 150℃exhibited the highest elongation(19.6%)due to uniform and fine grains,along with lower dislocation density.Microscopic observation,and electrochemical and immersion tests highlighted the significant influence of annealing temperature on corrosion rates.Alloy wires annealed at 150℃demonstrated superior corrosion resistance,which is attributed to small and uniform grains,low stress,and a well-distributed nano-second phase.Finally,the alloy wires annealed at 150℃exhibited enhanced comprehensive properties,making them good candidates for degradable staples.展开更多
In our previous work,die cast LA42(Mg-4La-2.5Al-0.3Mn,wt.%)alloy with an excellent combination of thermal-conducting performance and mechanical properties was developed.This study,taking commercial die cast AZ91(Mg-9A...In our previous work,die cast LA42(Mg-4La-2.5Al-0.3Mn,wt.%)alloy with an excellent combination of thermal-conducting performance and mechanical properties was developed.This study,taking commercial die cast AZ91(Mg-9Al-1 Zn,wt.%)alloy as a comparison,investigates the microstructure and corrosion behavior of the LA42 alloy in chloride-containing environment.The findings revealed that the microstructure of die cast LA42 alloy displays an Al-depletedα-Mg dendrite and a network shape eutectic phase comprising of eutecticα-Mg and lamellar Al11La3.The LA42 alloy exhibited slightly inferior corrosion resistance and deeper corrosion pits than the AZ91 alloy,which were related to the interphase attack and the presence of a layer of corrosion products containing more magnesium hydroxide of the LA42alloy.The corrosion behavior of the LA42 alloy was characterized by an interphase attack on the periphery of Al-depletedα-Mg dendrite adjacent to Al_(11)La_(3),which primarily ascribed to the relatively lower potential of the Al-depletedα-Mg phase and the interfacial reactivity between it and the adjacent Al_(11)La_(3),whereas the AZ91 alloy showed a trait of preferential corrosion of the interior ofα-Mg dendrite for its lowest potential among different phases.This comprehensive research can provide a guidance for future alloy design of Mg-Al-La alloys and their industrial applications.展开更多
The corrosion behavior of CoCrCu_(0.1)FeMoNi high entropy alloy(HEA)in 0.5 mol/L NaOH solution was investigated using X-ray photoelectron spectroscopy,X-ray diffraction,scanning electron microscopy,potentiodynamic pol...The corrosion behavior of CoCrCu_(0.1)FeMoNi high entropy alloy(HEA)in 0.5 mol/L NaOH solution was investigated using X-ray photoelectron spectroscopy,X-ray diffraction,scanning electron microscopy,potentiodynamic polarization measurement,and electrochemical impedance spectroscopy.The results showed that the microstructure of this HEA displayed a dendritic morphology along with inter-dendritic regions.At the applied potential of–0.3,0,and 0.1 V vs.saturated calomel electrode(SCE),no significant damage to the surface of the alloy was observed.At the applied potentials of 0.15 and 0.2 V vs.SCE,selective detachment and tearing of the microstructure on the alloy surface were observed,attributed to micro-galvanic corrosion.HEA demonstrates typical spontaneous passivation behavior and exhibits capacitance at all five applied potentials.The energy dispersive spectroscopy results indicate significant elemental segregation within HEA,with a decrease in the content of Cr_(2)O_(3)in the passive film as the applied potential increases.Consequently,the protective efficacy of the passive film over the substrate in 0.5 mol/L NaOH solution was compromised.展开更多
Mg?1Zn?0.5Ca alloys were prepared by traditional steel mould casting and water-cooled copper mould injection casting at higher cooling rate. Microstructure, mechanical properties and bio-corrosion resistance of two al...Mg?1Zn?0.5Ca alloys were prepared by traditional steel mould casting and water-cooled copper mould injection casting at higher cooling rate. Microstructure, mechanical properties and bio-corrosion resistance of two alloys were contrastively investigated. Grain size reduces remarkably and microstructure becomes homogenous when raising cooling rate. The bio-corrosion behaviour in 3.5% sodium chloride solution (3.5% NaCl) and Hank’s solution at 37°C was investigated using electrochemical polarization measurement and the results indicate that the alloy prepared at higher cooling rates has better corrosion resistance in both types of solution. Further mass loss immersion test in Hank’s solution reveals the same result. The reason of corrosion resistance improvement is that raising cooling rate brings about homogeneous microstructure, which leads to micro-galvanic corrosion alleviation. The tensile test results show that yield strength, ultimate tensile strength and elongation are improved by raising cooling rate and the improvement is mainly due to grain refinement.展开更多
The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phas...The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phase.The morphology of the second phase at the grain boundary differed in both alloys:it was a continuous network structure in Mg-10Gd-6Zn,whereas it was relatively discrete in Mg-10Gd-2Zn.The dendrites were finer in size and highly branched in Mg-10Gd-6Zn.The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn alloys.Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode,however,filiform corrosion dominated in the later stage,which was facilitated by the LPSO phase in the matrix.Severe micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second phase.The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times.Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times,and was removed by the chromic acid used for the corrosion product removal.展开更多
Marine biofouling is a major issue deteriorating the service performance and lifespan of marine infrastructures.The development of a durable,long-term,and environment-friendly antifouling coating is therefore of signi...Marine biofouling is a major issue deteriorating the service performance and lifespan of marine infrastructures.The development of a durable,long-term,and environment-friendly antifouling coating is therefore of significant importance but still a critical challenge in maritime engineering.Herein,we developed a Cu-Ti composite antifouling coating with micron-sized alternating laminated-structure of Cu/Ti by plasma spraying of mechanically mixed Cu/Ti powders.The coating was designed to enable controlled release of Cu ions through galvanic dissolution of Cu laminates from the Cu/Ti micro-galvanic cell in aqueous solution.Results showed that remarkable antifouling efficiency against bacterial survival and adhesion up to~100%was achieved for the Cu-Ti coating.Cu/Ti micro-galvanic cell was in-situ formed within Cu-Ti coating and responsible for its Cu ions release.The successive dissolution of Cu laminates resulted in the formation of micro-channels under Ti laminates near surface,which contributed to controlled slow Cu ions release and self-polishing effect.Thus,environment-friendly antifouling capability and∼200%longer antifouling lifetime than that of the conventional organic antifouling coatings can be achieved for the Cu-Ti coating.On the other hand,as compared to the conventional organic antifouling coatings,the Cu-Ti composite coating presented much higher mechanical durability due to its strong adhesion strength,excellent mechanical properties,and two orders lower wear rate.The present laminated Cu-Ti coating exhibits combination of outstanding antifouling performance and high mechanical durability,which makes this coating very potentially candidates in marine antifouling application.展开更多
Mg-Sn-Y alloys with different Sn contents(wt%)were assessed as anode candidates for Mg-air batteries.The relationship between microstructure(including the second phase,grain size,and texture)and discharge properties o...Mg-Sn-Y alloys with different Sn contents(wt%)were assessed as anode candidates for Mg-air batteries.The relationship between microstructure(including the second phase,grain size,and texture)and discharge properties of the Mg-Sn-Y alloys was examined using microstructure observation,electrochemical measurements,and galvanostatic discharge tests.The Mg-0.7Sn-1.4Y alloy had a high steady discharge voltage of 1.5225 V and a high anodic efficiency of 46.6% at 2.5 mA·cm^(-2).These good properties were related to its microstructure:small grain size of 3.8μm,uniform distribution of small second phase particles of 0.6μm,and a high content(vol%)of(1120)/(1010)orientated grains.The scanning Kelvin probe force microscopy(SKPFM)indicated that the Sn_(3)Y_(5) and MgSnY phases were effective cathodes causing micro-galvanic corrosion which promoted the dissolution of Mg matrix during the discharge process.展开更多
Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources.He...Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources.Here,a novel functional peak-aged Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu-0.4Ni(wt.%) alloy for fracturing tools is reported,and it possesses an ultimate tensile strength of 457.6 MPa,ultimate compressive strength of 620.7 MPa and dissolution rate of ~43.7 mg·cm^(-2)·h^(-1) in 3 wt.% KCl solutions at 93℃.The excellent strength of the agedalloy is primarily attributed to the combination of grain refinement,long-period stacking ordered(LPSO) strengthening,and precipitation strengthening induced by stacking fault and β’ phase,among which the precipitation strengthening is dominant.Further investigations confirm that the corrosion is triggered from the micro-galvanic coupling between the Mg matrix and the cathodic lamellar and block LPSO phases.Strip-shaped corrosion pits along with LPSO phases are subsequently formed,significantly accelerating corrosion.The β’ precipitates can effectively improve the strength without compromising the dissolution rate because of their nanoscale size.This study provides an excellent material selection for dissolvable fracturing tools and presents a strategy by which a synergistic combination of strength and dissolution rate is achieved via peak-aging treatment.展开更多
The limited wide applicability of commercial Mg alloys is mainly attributed to the poor corrosion resistance.Addition of alloying elements is the simplest and effective method to improve the corrosion properties.Based...The limited wide applicability of commercial Mg alloys is mainly attributed to the poor corrosion resistance.Addition of alloying elements is the simplest and effective method to improve the corrosion properties.Based on the low-cost alloy composition design,the corro-sion behavior of commercial Mg-3Al-1Zn(AZ31)alloy bearing minor Ca or Sn element was characterized by scanning Kelvin probe force microscopy,hydrogen evolution,electrochemical measurements,and corrosion morphology analysis.Results revealed that the potential differ-ence of Al_(2)Ca/α-Mg and Mg_(2)Sn/α-Mg was(230±19)mV and(80±6)mV,respectively,much lower than that of Al_(8)Mn_(5)/α-Mg(430±31)mV in AZ31 alloy,which illustrated that AZ31-0.2Sn alloy performed the best corrosion resistance,followed by AZ31-0.2Ca,while AZ31 al-loy exhibited the worst corrosion resistance.Moreover,Sn dissolved into matrix obviously increased the potential ofα-Mg and participated in the formation of dense SnO_(2) film at the interface of matrix,while Ca element was enriched in the corrosion product layer,resulting in the cor-rosion product layer of AZ31-0.2Ca/Sn alloys more compact,stable,and protective than AZ31 alloy.Therefore,AZ31 alloy bearing 0.2wt%Ca or Sn element exhibited excellent balanced properties,which is potential to be applied in commercial more comprehensively.展开更多
Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5 Cu alloy,Mg-2.5 Cu-6.0 Al alloy exhibits an improved compressive strength of 378 MPa and compressive str...Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5 Cu alloy,Mg-2.5 Cu-6.0 Al alloy exhibits an improved compressive strength of 378 MPa and compressive strain of 27%,combined with a high degradation rate of 383 mm/y.Two kinds of second-phases are found in Mg-Cu-Al alloys,i.e.MgAlCu andβ-Mg_(17)Al_(12)+Al_(2)Cu phases.They form a discontinuous network and act as cathodes for micro-galvanic corrosion,leading to a high degradation rate.Moreover,the addition of Al could improve the strength and ductility simultaneously in Mg-Cu alloys.The enhancement of strength primarily arises from the solid-solution strengthening and second-phase hardening.A high density of basal,non-basal dislocations and stacking faults were activated upon mechanical deformation.This accounts for the good ductility in Mg-Cu-Al alloys.展开更多
The corrosion behaviour of Mg−6Gd−3Y−1Zn−0.3Ag(wt.%)alloy components with different sizes after cooling was investigated.The alloys in the small components(SC)cooled fast,which were composed ofα-Mg matrix and coarse ...The corrosion behaviour of Mg−6Gd−3Y−1Zn−0.3Ag(wt.%)alloy components with different sizes after cooling was investigated.The alloys in the small components(SC)cooled fast,which were composed ofα-Mg matrix and coarse long-period stacking ordered(LPSO)phases.The alloys in the large components(LC)cooled slowly,and there were thin lamellar LPSO phases precipitating inside the grains,except forα-Mg matrix and coarse LPSO phases.The hydrogen evolution test revealed that the corrosion rate of LC sample was higher than that of SC sample.Electrochemical impedance spectroscopy(EIS)test showed that the surface film on LC alloys provided worse protection.The corrosion morphologies indicated that the precipitation of the thin lamellar LPSO phases in LC sample caused severe micro-galvanic corrosion,which accelerated the rupture of the surface film.展开更多
The effect of textures on different surfaces of an as-extruded Mg-4 Al-1 Sn-1 Zn(ATZ411) alloy sheet on its corrosion behavior was systematically investigated. The microstructure was examined by optical/scanning elect...The effect of textures on different surfaces of an as-extruded Mg-4 Al-1 Sn-1 Zn(ATZ411) alloy sheet on its corrosion behavior was systematically investigated. The microstructure was examined by optical/scanning electron microscopy. The texture was characterized by X-ray diffraction and electron backscatter diffraction. The corrosion performance was evaluated by immersion tests, electrochemical measurements, and corrosion morphology observation. The results showed that there were obvious differences in the corrosion morphology and corrosion resistance on different surfaces. The surface perpendicular to extrusion direction had better corrosion resistance and more uniform corrosion damage than that perpendicular to the normal direction and that perpendicular to the transverse direction in 3.5 wt% NaCl solution. The corrosion morphology was mainly determined by the distribution of the second phase and fine-grained regions. The corrosion rate was more related to the overall texture.展开更多
In this study,the effects of Al addition on the corrosion behavior of pure Mg with controlled impurity contents were systematically analyzed according to the processing history.The results revealed that the corrosion ...In this study,the effects of Al addition on the corrosion behavior of pure Mg with controlled impurity contents were systematically analyzed according to the processing history.The results revealed that the corrosion behavior of high-purity Mg-Al alloys is strongly related to changes in the microstructure,including theβphase and Al-Mn or Al-Fe phases,and the protectiveness of the surface film according to the Al content and processing history.In the as-cast alloys,the corrosion rate increased due to the increase ofβphase as the Al content increased,but in the as-extruded alloys,the corrosion rate,which was high due to intermetallic compounds caused by impurities in the low Al alloy,decreased as the Al content increased,and then increased again.This is due to the combined effect of the increase of theβphase and decrease of the impurity effect,and the increase of the dissolved Al content.The results suggest that it is necessary to analyze the effect of alloying elements on the corrosion behavior of pure Mg with information concerning the impurity content and processing history.展开更多
Mg-Zn-Y alloys with long-period stacking ordered structures were prepared by an ingot casting method. The corrosion performance of Mg-Zn-Y alloys was studied by combining gas-collecting test, immersion test and electr...Mg-Zn-Y alloys with long-period stacking ordered structures were prepared by an ingot casting method. The corrosion performance of Mg-Zn-Y alloys was studied by combining gas-collecting test, immersion test and electrochemical measurements in order to determine the corrosion rate and mechanism of the alloys. The results showed that the volume fraction of Mg（12）YZn phase increased and the shape of the Mg（12）YZn phase changed from discontinuous to continuous net-like with increasing Zn and Y content. The corrosion rate of the alloys greatly depended on the distribution and volume fraction of the Mg（12）YZn phase. Corrosion products appeared at the junction of Mg phase and Mg（12）YZn phase, indicating that the Mg（12）YZn phase accelerated galvanic corrosion of Mg matrix. Mg（97）Zn1Y2 alloy shows the lowest corrosion rate due to the continuous distribution of Mg（12）YZn phase.展开更多
Minimally invasive surgery(MIS)robots,such as single-arm stapling robots,are key to oral and maxillofacial surgery because they overcome space constraints in the oral cavity and deep throat.However,biodegradable sutur...Minimally invasive surgery(MIS)robots,such as single-arm stapling robots,are key to oral and maxillofacial surgery because they overcome space constraints in the oral cavity and deep throat.However,biodegradable suture staples should be developed for the single-arm stapling robots to avoid a secondary operation.For this aim,a new type of Mg-3Zn-0.2Ca-2Ag biodegradable alloy wire was developed in this study applied as suture staples.Its tensile strength,yield strength,and elongation are 326.1 MPa,314.5 MPa,and 19.6%,respectively.Especially,the alloy wire attains the highest yield strength value reported among all the biodegradable Mg wires,which is mainly attributed to fine grain strengthening and second phase strengthening such as Mg_(2)Zn_(11) nano phase strengthening.Moreover,the corrosion rate of this alloy wire in simulated body fluid(SBF)reaches 26.8 mm/y,the highest value among all the biodegradable Mg alloy wires reported so far,which is mainly from the intensified galvanic corrosion between the Ag17Mg54 phase and the Mg matrix.In vitro studies demonstrate that the alloy wire exhibits good blood compatibility and low cytotoxicity.The cone beam computed tomography(CBCT)data shows that the suture staple made of the Mg alloy wire provides better mechanical support in the early postoperative period.From the single arm robot tests,it confirms that suture staples can close the wound tightly and remain stable over time.This research provides a good material selection for the automated suturing in oral and throat surgery robots.展开更多
基金funded by the National Key Research and Development Program of China (Grant No. 2016YFB0301001 and 2016YFB0301101)Major Projects for Collaborative Innovation of Zhengzhou (Grant No.18XTZX12010)Certificate of Postdoctoral Research Grant in Henan Province (Grant No. 201903011)。
文摘Effect of the second phase in the micro-galvanic corrosion of a commercial Mg alloy containing rare earth elements, cast WE43 alloy,was investigated in 0.6 M NaCl solution and 0.6 M Na_(2)SO_(4)solution by scanning electron microscopy(SEM) observations, scanning Kelvin probe force microscopy(SKPFM) analysis, hydrogen evolution, weight loss measurement, and electrochemical techniques. It is confirmed that the second phase of cast WE43 alloy is more active than Mg matrix and exhibits an anodic role in the micro-galvanic corrosion with α-Mg matrix as cathode and dissolves preferentially in Na_(2)SO_(4)solution, in contrast to the situation in NaCl solution. The corrosion rate of cast WE43 alloy in Na_(2)SO_(4)solution is much higher than that in NaCl solution, which is different from the conventional wisdom and could be attributed to the different role of the second phase in the micro-galvanic corrosion in two solutions.
基金financial support of the Natural Science Foundation of Liaoning Province,China(2019JH3/30100037)the National Natural Science Foundation of China(No.U1867216)the State Key Laboratory of Metal Material for Marine Equipment and Application(No.SKLMEA-K201907)。
文摘The corrosion behavior of the as-received steel and the spheroidized steel in acidic chloride environment was investigated. The results indicate the corrosion mode and corrosion rate of two steels are diverse due to their difference in microstructure. For as-received steel with ferrite-pearlite microstructure, severe localized corrosion happens on the pearlite regions, and plenty of cathodic cementite remains in the pits, further strengthening the micro-galvanic effect and accelerating the corrosion rate. While for spheroidized steel with tempered martensite microstructure, the nanosized cementite particles evenly distributed on the ferrite substrate are easy to fall off, which can significantly reduce the cementite accumulation on the steel surface, relieving the acceleration effect of micro-galvanic corrosion.
基金supported by JSPS KAKENHI Grant Numbers JP17H01331 and JP21K18804supported by The Light Metal Educational Foundation Inc.of Japansupported by Amano Institute of Technology and China Scholarship Council。
文摘A model specimen with a single boundary of theα/βphase simulating Mg-Al alloys was successfully fabricated by spark plasma sintering.A small electrode area ofαphase orβphase was prepared using the model specimen,and the OCPs(open-circuit potentials)of each phase and a small electrode area containing theα/βphase boundary in 0.1 M NaCl at pH 8.0 were compared:theβphase exhibited a higher potential,and theαphase showed a lower potential.The OCP of the small area containing theα/βphase boundary was the intermediate value of these phases.In a small area containingα/βphase boundary,discoloration and gas bubbles were observed on theαphase,but no bubble generation was detected on theβphase.The gas bubbles were initially generated on theαphase near theβphase,but as the discoloration(corrosion)of theαphase approached theβphase,the bubbles were generated on theβphase.In micro-galvanic corrosion of theαandβphases,theβphase did not always function as the preferred cathode.Theαphase partially corroded(or discolored)and became the anodes,so that the surrounding areas were most likely to be the cathodes.When corroded areas(anodes)in theαphase approached theβphase,theβphase would become cathodes.In addition to the micro-galvanic corrosion mechanism,the role of Al in corrosion resistance at theα/βphase boundary was determined by surface analysis.
基金financial support from the National Natural Science Foundation of China(No.51961026)。
文摘The localized micro-galvanic corrosion process and the kinetic information of Mg-(7,9)Al-1Fe-x Nd alloys were investigated by in situ observation under electrochemical control and in situ atomic force microscopy(AFM)in an electrolyte environment.The results revealed that the formation of the Nd-rich phase in alloys resulted in a decrease in the Volta potential difference from~400 m V(AlFe3/α-Mg)to~220 mV(Nd-rich/α-Mg),reducing the corrosion products around the cathodic phase and corrosion current density of the microscale area.The addition of Nd significantly improved the corrosion resistance,mainly due to the suppression of the micro-galvanic corrosion between the second phases and substrate.Finally,the corrosion mechanism of Mg-(7,9)Al-1Fe-x Nd alloys was discussed based on in situ observations and electrochemical results.
基金support by the National Natural Science Foundation of China(No.51961026).
文摘The phosphate protective film and micro-galvanic corrosion of biological Mg-3Zn-xNd (x = 0, 0.6, 1.2) alloys were investigated by scanning and transmission electron microscopy, quasi-in-situ observation, scanning Kelvin probe force microscopy (SKPFM) and electrochemical tests. The results revealed the Mg-Zn-Nd phases formed in Mg-3Zn alloy contained with Nd. Adding Nd resulted in a significant decline in the cracks of the phosphate protective film and micro-galvanic corrosion of alloys, which were recorded by quasi-in-situ observation. In addition, the Volta potential difference of Mg-Zn-Nd/α-Mg (~ 188 mV) was lower than MgZn/α-Mg (~ 419 mV) and Zn-rich/α-Mg (~ 260 mV), and the corrosion rates of alloys markedly decreased after the addition of 0.6 wt% Nd. The improvement in corrosion resistance of Nd-containing alloys was mainly attributed to the following: (i) the addition of Nd reduced the Volta potential difference (second phases/α-Mg);(ii) the phosphate protective film containing Nd_(2)O_(3) deposited on the surface of the alloys, effectively preventing the penetration of harmful anions.
基金The National Natural Science Foundation of China(Nos.51971020,52171097)the Major State Research and Development Program of China(No.2021YFB3701100)+1 种基金Key Scientific Research Project in Shanxi Province,China(No.202102050201003)the Opening Research Fund of State Key Laboratory for Advanced Metals and Materials,China(No.2023-Z03).
文摘In response to the interest in degradable magnesium staples for oral and maxillofacial surgical procedures,high-performance Mg−3Zn−0.2Ca−2Ag alloy wires were reported.The impact of annealing temperature on the mechanical properties and corrosion behavior of the alloy wires was investigated.Results indicated that an increased annealing temperature led to grain growth,reduced the volume fraction of the second phase,and lowered dislocation density,causing decreased strength.The alloy annealed at 150℃exhibited the highest elongation(19.6%)due to uniform and fine grains,along with lower dislocation density.Microscopic observation,and electrochemical and immersion tests highlighted the significant influence of annealing temperature on corrosion rates.Alloy wires annealed at 150℃demonstrated superior corrosion resistance,which is attributed to small and uniform grains,low stress,and a well-distributed nano-second phase.Finally,the alloy wires annealed at 150℃exhibited enhanced comprehensive properties,making them good candidates for degradable staples.
基金supports from the collaboration research item between Shanghai Jiao Tong University and Hitachi(China)Ltdsupported by Qinghai Salt Lake Industry Co.Ltd financially by via of the Science and Technology Project(21-ZC0609-0003)the National Natural Science Foundation of China(No.51825101)。
文摘In our previous work,die cast LA42(Mg-4La-2.5Al-0.3Mn,wt.%)alloy with an excellent combination of thermal-conducting performance and mechanical properties was developed.This study,taking commercial die cast AZ91(Mg-9Al-1 Zn,wt.%)alloy as a comparison,investigates the microstructure and corrosion behavior of the LA42 alloy in chloride-containing environment.The findings revealed that the microstructure of die cast LA42 alloy displays an Al-depletedα-Mg dendrite and a network shape eutectic phase comprising of eutecticα-Mg and lamellar Al11La3.The LA42 alloy exhibited slightly inferior corrosion resistance and deeper corrosion pits than the AZ91 alloy,which were related to the interphase attack and the presence of a layer of corrosion products containing more magnesium hydroxide of the LA42alloy.The corrosion behavior of the LA42 alloy was characterized by an interphase attack on the periphery of Al-depletedα-Mg dendrite adjacent to Al_(11)La_(3),which primarily ascribed to the relatively lower potential of the Al-depletedα-Mg phase and the interfacial reactivity between it and the adjacent Al_(11)La_(3),whereas the AZ91 alloy showed a trait of preferential corrosion of the interior ofα-Mg dendrite for its lowest potential among different phases.This comprehensive research can provide a guidance for future alloy design of Mg-Al-La alloys and their industrial applications.
基金funded by National Key Research and Development Program of China(No.2021YFB3401100)Evaluation Project of Guangdong Provincial Key Laboratory(No.2023B1212060043)+1 种基金Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001)GDAS'Project of Science and Technology Development(Nos.2023GDASQNRC-0205 and 2024GDASZH-2024010102).
文摘The corrosion behavior of CoCrCu_(0.1)FeMoNi high entropy alloy(HEA)in 0.5 mol/L NaOH solution was investigated using X-ray photoelectron spectroscopy,X-ray diffraction,scanning electron microscopy,potentiodynamic polarization measurement,and electrochemical impedance spectroscopy.The results showed that the microstructure of this HEA displayed a dendritic morphology along with inter-dendritic regions.At the applied potential of–0.3,0,and 0.1 V vs.saturated calomel electrode(SCE),no significant damage to the surface of the alloy was observed.At the applied potentials of 0.15 and 0.2 V vs.SCE,selective detachment and tearing of the microstructure on the alloy surface were observed,attributed to micro-galvanic corrosion.HEA demonstrates typical spontaneous passivation behavior and exhibits capacitance at all five applied potentials.The energy dispersive spectroscopy results indicate significant elemental segregation within HEA,with a decrease in the content of Cr_(2)O_(3)in the passive film as the applied potential increases.Consequently,the protective efficacy of the passive film over the substrate in 0.5 mol/L NaOH solution was compromised.
基金Project(20921002)supported by the Innovative Research Groups of the National Natural Science Foundation of ChinaProject(21221061)supported by the National Natural Science Foundation of China+1 种基金Project(201105007)supported by the Science and Technology Program of Jilin Province,ChinaProject(20140325003GX)supported by the Science and Technology Support Project of Jilin Province,China
文摘Mg?1Zn?0.5Ca alloys were prepared by traditional steel mould casting and water-cooled copper mould injection casting at higher cooling rate. Microstructure, mechanical properties and bio-corrosion resistance of two alloys were contrastively investigated. Grain size reduces remarkably and microstructure becomes homogenous when raising cooling rate. The bio-corrosion behaviour in 3.5% sodium chloride solution (3.5% NaCl) and Hank’s solution at 37°C was investigated using electrochemical polarization measurement and the results indicate that the alloy prepared at higher cooling rates has better corrosion resistance in both types of solution. Further mass loss immersion test in Hank’s solution reveals the same result. The reason of corrosion resistance improvement is that raising cooling rate brings about homogeneous microstructure, which leads to micro-galvanic corrosion alleviation. The tensile test results show that yield strength, ultimate tensile strength and elongation are improved by raising cooling rate and the improvement is mainly due to grain refinement.
文摘The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phase.The morphology of the second phase at the grain boundary differed in both alloys:it was a continuous network structure in Mg-10Gd-6Zn,whereas it was relatively discrete in Mg-10Gd-2Zn.The dendrites were finer in size and highly branched in Mg-10Gd-6Zn.The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn alloys.Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode,however,filiform corrosion dominated in the later stage,which was facilitated by the LPSO phase in the matrix.Severe micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second phase.The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times.Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times,and was removed by the chromic acid used for the corrosion product removal.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52001280 and 51875443)the Key Research Project of Henan Province(No.20A430029)the China Postdoctoral Science Foundation(No.2020M682339)。
文摘Marine biofouling is a major issue deteriorating the service performance and lifespan of marine infrastructures.The development of a durable,long-term,and environment-friendly antifouling coating is therefore of significant importance but still a critical challenge in maritime engineering.Herein,we developed a Cu-Ti composite antifouling coating with micron-sized alternating laminated-structure of Cu/Ti by plasma spraying of mechanically mixed Cu/Ti powders.The coating was designed to enable controlled release of Cu ions through galvanic dissolution of Cu laminates from the Cu/Ti micro-galvanic cell in aqueous solution.Results showed that remarkable antifouling efficiency against bacterial survival and adhesion up to~100%was achieved for the Cu-Ti coating.Cu/Ti micro-galvanic cell was in-situ formed within Cu-Ti coating and responsible for its Cu ions release.The successive dissolution of Cu laminates resulted in the formation of micro-channels under Ti laminates near surface,which contributed to controlled slow Cu ions release and self-polishing effect.Thus,environment-friendly antifouling capability and∼200%longer antifouling lifetime than that of the conventional organic antifouling coatings can be achieved for the Cu-Ti coating.On the other hand,as compared to the conventional organic antifouling coatings,the Cu-Ti composite coating presented much higher mechanical durability due to its strong adhesion strength,excellent mechanical properties,and two orders lower wear rate.The present laminated Cu-Ti coating exhibits combination of outstanding antifouling performance and high mechanical durability,which makes this coating very potentially candidates in marine antifouling application.
文摘Mg-Sn-Y alloys with different Sn contents(wt%)were assessed as anode candidates for Mg-air batteries.The relationship between microstructure(including the second phase,grain size,and texture)and discharge properties of the Mg-Sn-Y alloys was examined using microstructure observation,electrochemical measurements,and galvanostatic discharge tests.The Mg-0.7Sn-1.4Y alloy had a high steady discharge voltage of 1.5225 V and a high anodic efficiency of 46.6% at 2.5 mA·cm^(-2).These good properties were related to its microstructure:small grain size of 3.8μm,uniform distribution of small second phase particles of 0.6μm,and a high content(vol%)of(1120)/(1010)orientated grains.The scanning Kelvin probe force microscopy(SKPFM)indicated that the Sn_(3)Y_(5) and MgSnY phases were effective cathodes causing micro-galvanic corrosion which promoted the dissolution of Mg matrix during the discharge process.
基金The Major State Research and Development Program of China (No. 2021YFB3701100, No. SQ2020YFF0405156)the National Natural Science Foundation of China (No.52171097, No. 51971020)+2 种基金Beijing Laboratory of Metallic Materials and Processing for Modern Transportationthe Fundamental Research Funds for the Central Universities(No. FRF-IC-20–08)“Dingxinbeike” Project(G20200001105) for the international communication。
文摘Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources.Here,a novel functional peak-aged Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu-0.4Ni(wt.%) alloy for fracturing tools is reported,and it possesses an ultimate tensile strength of 457.6 MPa,ultimate compressive strength of 620.7 MPa and dissolution rate of ~43.7 mg·cm^(-2)·h^(-1) in 3 wt.% KCl solutions at 93℃.The excellent strength of the agedalloy is primarily attributed to the combination of grain refinement,long-period stacking ordered(LPSO) strengthening,and precipitation strengthening induced by stacking fault and β’ phase,among which the precipitation strengthening is dominant.Further investigations confirm that the corrosion is triggered from the micro-galvanic coupling between the Mg matrix and the cathodic lamellar and block LPSO phases.Strip-shaped corrosion pits along with LPSO phases are subsequently formed,significantly accelerating corrosion.The β’ precipitates can effectively improve the strength without compromising the dissolution rate because of their nanoscale size.This study provides an excellent material selection for dissolvable fracturing tools and presents a strategy by which a synergistic combination of strength and dissolution rate is achieved via peak-aging treatment.
基金This work is financially supported by the Fundamental Research Funds for the Central Universities,China(Nos.2302017FRF-IC-17-001,2302018FRF-IC-18-004,232019 FRF-IC-19-018,and 2302020FRF-IC-20-10)the China Postdoctoral Science Foundation(No.2021M700378).
文摘The limited wide applicability of commercial Mg alloys is mainly attributed to the poor corrosion resistance.Addition of alloying elements is the simplest and effective method to improve the corrosion properties.Based on the low-cost alloy composition design,the corro-sion behavior of commercial Mg-3Al-1Zn(AZ31)alloy bearing minor Ca or Sn element was characterized by scanning Kelvin probe force microscopy,hydrogen evolution,electrochemical measurements,and corrosion morphology analysis.Results revealed that the potential differ-ence of Al_(2)Ca/α-Mg and Mg_(2)Sn/α-Mg was(230±19)mV and(80±6)mV,respectively,much lower than that of Al_(8)Mn_(5)/α-Mg(430±31)mV in AZ31 alloy,which illustrated that AZ31-0.2Sn alloy performed the best corrosion resistance,followed by AZ31-0.2Ca,while AZ31 al-loy exhibited the worst corrosion resistance.Moreover,Sn dissolved into matrix obviously increased the potential ofα-Mg and participated in the formation of dense SnO_(2) film at the interface of matrix,while Ca element was enriched in the corrosion product layer,resulting in the cor-rosion product layer of AZ31-0.2Ca/Sn alloys more compact,stable,and protective than AZ31 alloy.Therefore,AZ31 alloy bearing 0.2wt%Ca or Sn element exhibited excellent balanced properties,which is potential to be applied in commercial more comprehensively.
文摘Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5 Cu alloy,Mg-2.5 Cu-6.0 Al alloy exhibits an improved compressive strength of 378 MPa and compressive strain of 27%,combined with a high degradation rate of 383 mm/y.Two kinds of second-phases are found in Mg-Cu-Al alloys,i.e.MgAlCu andβ-Mg_(17)Al_(12)+Al_(2)Cu phases.They form a discontinuous network and act as cathodes for micro-galvanic corrosion,leading to a high degradation rate.Moreover,the addition of Al could improve the strength and ductility simultaneously in Mg-Cu alloys.The enhancement of strength primarily arises from the solid-solution strengthening and second-phase hardening.A high density of basal,non-basal dislocations and stacking faults were activated upon mechanical deformation.This accounts for the good ductility in Mg-Cu-Al alloys.
基金the financial supports from the National Natural Science foundation of China(Nos.51574291,51874367).
文摘The corrosion behaviour of Mg−6Gd−3Y−1Zn−0.3Ag(wt.%)alloy components with different sizes after cooling was investigated.The alloys in the small components(SC)cooled fast,which were composed ofα-Mg matrix and coarse long-period stacking ordered(LPSO)phases.The alloys in the large components(LC)cooled slowly,and there were thin lamellar LPSO phases precipitating inside the grains,except forα-Mg matrix and coarse LPSO phases.The hydrogen evolution test revealed that the corrosion rate of LC sample was higher than that of SC sample.Electrochemical impedance spectroscopy(EIS)test showed that the surface film on LC alloys provided worse protection.The corrosion morphologies indicated that the precipitation of the thin lamellar LPSO phases in LC sample caused severe micro-galvanic corrosion,which accelerated the rupture of the surface film.
基金Financially supported by the National Natural Science Foundation of China(No.51804130)the Natural Science Foundation Project of Jilin Province(No.20170101159JC)the Science and Technology Development Project of Jilin Province(No.20180520209JH)。
文摘The effect of textures on different surfaces of an as-extruded Mg-4 Al-1 Sn-1 Zn(ATZ411) alloy sheet on its corrosion behavior was systematically investigated. The microstructure was examined by optical/scanning electron microscopy. The texture was characterized by X-ray diffraction and electron backscatter diffraction. The corrosion performance was evaluated by immersion tests, electrochemical measurements, and corrosion morphology observation. The results showed that there were obvious differences in the corrosion morphology and corrosion resistance on different surfaces. The surface perpendicular to extrusion direction had better corrosion resistance and more uniform corrosion damage than that perpendicular to the normal direction and that perpendicular to the transverse direction in 3.5 wt% NaCl solution. The corrosion morphology was mainly determined by the distribution of the second phase and fine-grained regions. The corrosion rate was more related to the overall texture.
基金the main research program of the Korea Institute of Materials Science(Grant No.PNK8150)for financially supporting this study
文摘In this study,the effects of Al addition on the corrosion behavior of pure Mg with controlled impurity contents were systematically analyzed according to the processing history.The results revealed that the corrosion behavior of high-purity Mg-Al alloys is strongly related to changes in the microstructure,including theβphase and Al-Mn or Al-Fe phases,and the protectiveness of the surface film according to the Al content and processing history.In the as-cast alloys,the corrosion rate increased due to the increase ofβphase as the Al content increased,but in the as-extruded alloys,the corrosion rate,which was high due to intermetallic compounds caused by impurities in the low Al alloy,decreased as the Al content increased,and then increased again.This is due to the combined effect of the increase of theβphase and decrease of the impurity effect,and the increase of the dissolved Al content.The results suggest that it is necessary to analyze the effect of alloying elements on the corrosion behavior of pure Mg with information concerning the impurity content and processing history.
基金support of the National Natural Science Foundation of China (No.50571073)the Ph.D. Programs Foundation of Ministry of Education of China (No. 20111402110004)the Natural Science Foundation of Shanxi Province, China (No.2009011028-3)
文摘Mg-Zn-Y alloys with long-period stacking ordered structures were prepared by an ingot casting method. The corrosion performance of Mg-Zn-Y alloys was studied by combining gas-collecting test, immersion test and electrochemical measurements in order to determine the corrosion rate and mechanism of the alloys. The results showed that the volume fraction of Mg（12）YZn phase increased and the shape of the Mg（12）YZn phase changed from discontinuous to continuous net-like with increasing Zn and Y content. The corrosion rate of the alloys greatly depended on the distribution and volume fraction of the Mg（12）YZn phase. Corrosion products appeared at the junction of Mg phase and Mg（12）YZn phase, indicating that the Mg（12）YZn phase accelerated galvanic corrosion of Mg matrix. Mg（97）Zn1Y2 alloy shows the lowest corrosion rate due to the continuous distribution of Mg（12）YZn phase.
基金supported by the National Key R&D Program of China(grant number:2020YFB1312801)the National Natural Science Foundation of China(No.51971020,No.52171097)+4 种基金the Opening Research Fund of State Key Laboratory for Advanced Metals and Materials(2021-Z08)the Fundamental Research Funds for the Central Universities(grant number:PKU2022XGK005)the Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences(2022-JKCS-24)the Key Scientific Research Project in Shanxi Province(202102050201003)the“Dingxinbeike”Project(G20200001105).
文摘Minimally invasive surgery(MIS)robots,such as single-arm stapling robots,are key to oral and maxillofacial surgery because they overcome space constraints in the oral cavity and deep throat.However,biodegradable suture staples should be developed for the single-arm stapling robots to avoid a secondary operation.For this aim,a new type of Mg-3Zn-0.2Ca-2Ag biodegradable alloy wire was developed in this study applied as suture staples.Its tensile strength,yield strength,and elongation are 326.1 MPa,314.5 MPa,and 19.6%,respectively.Especially,the alloy wire attains the highest yield strength value reported among all the biodegradable Mg wires,which is mainly attributed to fine grain strengthening and second phase strengthening such as Mg_(2)Zn_(11) nano phase strengthening.Moreover,the corrosion rate of this alloy wire in simulated body fluid(SBF)reaches 26.8 mm/y,the highest value among all the biodegradable Mg alloy wires reported so far,which is mainly from the intensified galvanic corrosion between the Ag17Mg54 phase and the Mg matrix.In vitro studies demonstrate that the alloy wire exhibits good blood compatibility and low cytotoxicity.The cone beam computed tomography(CBCT)data shows that the suture staple made of the Mg alloy wire provides better mechanical support in the early postoperative period.From the single arm robot tests,it confirms that suture staples can close the wound tightly and remain stable over time.This research provides a good material selection for the automated suturing in oral and throat surgery robots.
