The corrosion resistance and mechanical properties were tested and compared for the newly synthesized as-cast,as-solution Ni-Cr-Mo-Cu corrosion resistant alloys and 1Cr18Ni9Ti austenitic stainless steel. Their valence...The corrosion resistance and mechanical properties were tested and compared for the newly synthesized as-cast,as-solution Ni-Cr-Mo-Cu corrosion resistant alloys and 1Cr18Ni9Ti austenitic stainless steel. Their valence electron structural units were constructed,and the relative parameters were calculated by means of the Empirical Electron theory of Solids and Molecules(EET). The results show that,during alloy elements Cr,Mo and Cu entering Ni-matrix,the bonding strength nA and bonding energy EA of the strongest bond of the alloy are greatly increased,causing the stronger solid solution strengthening effects(about 30% increase in σb). Also,as reinforcement of the main bond network and the improvement of stability of the alloy system due to the solution of these alloying elements in γ-Ni,the ionization of metal atoms in corrosion solution and the flow of electrons from anode to cathode would all be impeded during electro-chemical corrosion processes,which leads to the excellent corrosion resistant ability of the present Ni-Cr-Mo-Cu alloy(about 2-3 orders of magnitude as high as 1Cr18Ni9Ti austenitic stainless steel) in several highly aggressive solutions.展开更多
An extruded Mg-4Zn-0.2Mn-0.2Ca alloy was developed as potential biodegradable bone-plate due to its excellent biocompatibility.Long term in vitro immersion in Hank’s solution and bending test were used to evaluate th...An extruded Mg-4Zn-0.2Mn-0.2Ca alloy was developed as potential biodegradable bone-plate due to its excellent biocompatibility.Long term in vitro immersion in Hank’s solution and bending test were used to evaluate the degradability and the mechanical integrity of the alloy.The results revealed that the degradation rate of the bone-plate increased in the first 7 days and then decreased with the prolonged immersion time before it finally reached a steady stage(about 0.84 mm/a)after immersion for 90 days.The bending strength after immersion for 60 days was 67.6 MPa,indicating that the bone-plate could support certain mechanical load after long term degradation.The formation of corrosion pits after degradation stemmed from the separation of the continuously distributed second phases from Mg matrix under the action of micro-galvanic couples.As a result,the mechanical performance of Mg-4Zn-0.2Mn-0.2Ca alloy was aggravated owing to the corrosion holes on its surface.展开更多
Compact anodic films with high hardness and good corrosion resistance on magnesium alloys were prepared by a new constant voltage and arc-free anodizing process. The effects of anodizing parameters such as applied vol...Compact anodic films with high hardness and good corrosion resistance on magnesium alloys were prepared by a new constant voltage and arc-free anodizing process. The effects of anodizing parameters such as applied voltage and electrolyte temperature on the peak current density and the thickness of films were investigated. In addition, the morphologies and corrosion resistance of films were investigated by scanning electron microscopy and potentiodynamic polarization, respectively. The results show that the higher the applied voltage, the higher the peak current density and the thicker the films. However, too high applied voltage may result in breakdown of films and intense sparking which may deteriorate the properties of the anodic films and bring about unsafety. The new anodizing process can be applied in a wide range of temperature. The new anodic films have numbers of pores with the diameter of 0.55.0μm which do not transverse the entire film.展开更多
The aspartic acid(ASP),an environment-friendly corrosion inhibitor,was explored to intercalate into the ZnAl-layered double hydroxide(ZnAl-LDH)and MgAl-LDH coatings on AZ31 magnesium alloys by a facile one-step hydrot...The aspartic acid(ASP),an environment-friendly corrosion inhibitor,was explored to intercalate into the ZnAl-layered double hydroxide(ZnAl-LDH)and MgAl-LDH coatings on AZ31 magnesium alloys by a facile one-step hydrothermal method.The morphology,composition,structure and corrosion resistance of the prepared coatings were comparatively investigated.It is found that the uniform and dense layered nanosheet(NS)vertically grows on the substrate,and the MgAl−ASP-LDH films exhibit a three-dimensional(3D)rose-like sheet structure with high ratio of pore coverage.The MgAl−ASP-LDH coating exhibits better corrosion resistance and durability of longtime immersion than ZnAl−ASP-LDH coating.The corrosion current density of two coatings is two or three orders of magnitude lower than that of bare Mg alloy,indicating that ZnAl/MgAl-LDH films intercalated with organic ASP anions can significantly improve the corrosion resistance of Mg alloy.展开更多
Nickel-based superalloys with and without Co by partial replacement of W were prepared using double vacuum melting.A comparison of the oxidation in air and hot corrosion behaviors under molten 75 wt.%Na2 SO4+25 wt.%Na...Nickel-based superalloys with and without Co by partial replacement of W were prepared using double vacuum melting.A comparison of the oxidation in air and hot corrosion behaviors under molten 75 wt.%Na2 SO4+25 wt.%NaCl at 900℃were systematically investigated.The results showed that partial replacement of W with Co promoted the formation of chromia scale and consequently decreased the oxidation rate.Besides,the addition of Co also retarded the internal oxidation/nitridation of Al and consequently promoted the growth of Al_(2) O3 scale,which further decreased the scaling rate and improved the adhesion of scale.Moreover,the addition of Co also further improved the hot corrosion resistance under molten Na2 SO4-NaCl salts.展开更多
To find suitable biodegradable materials for implant applications,Mg−6Zn−0.3Mn−xCa(x=0,0.2 and 0.5,wt.%)alloys were prepared by semi-continuous casting followed by hot-extrusion technique.The microstructure and mechan...To find suitable biodegradable materials for implant applications,Mg−6Zn−0.3Mn−xCa(x=0,0.2 and 0.5,wt.%)alloys were prepared by semi-continuous casting followed by hot-extrusion technique.The microstructure and mechanical properties of Mg−6Zn−0.3Mn−xCa alloys were investigated using the optical microscope,scanning electron microscope and tensile testing.Results indicated that minor Ca addition can slightly refine grains of the extruded Mg−6Zn−0.3Mn alloy and improve its strength.When 0.2 wt.%and 0.5 wt.%Ca were added,the grain sizes of the as-extruded alloys were refined from 4.8 to 4.6 and 4.2μm,respectively.Of the three alloys studied,the alloy with 0.5 wt.%Ca exhibits better combined mechanical properties with the ultimate tensile strength and elongation of 334 MPa and 20.3%.The corrosion behaviour,cell viability and antibacterial activities of alloys studied were also evaluated.Increasing Ca content deteriorates the corrosion resistance of alloys due to the increase of amount of effective cathodic sites caused by the formation of more Ca2Mg6Zn3 phases.Cytotoxicity evaluation with L929 cells shows higher cell viability of the Mg−6Zn−0.3Mn−0.5Ca alloy compared to Mg−6Zn−0.3Mn and Mg−6Zn−0.3Mn−0.2Ca alloys.The antibacterial activity against Staphylococcus aureus is enhanced with increasing the Ca content due to its physicochemical and biological performance in bone repairing process.展开更多
Silver and silver alloys usually tarnish,which causes some changes in their aesthetic appearance and electrical properties,due to their exposure to sulphide environments(H2S),and this is a problem in the field of corr...Silver and silver alloys usually tarnish,which causes some changes in their aesthetic appearance and electrical properties,due to their exposure to sulphide environments(H2S),and this is a problem in the field of corrosion and conservation of cultural heritage metallic artefacts.In this study,the role of copper content in the tarnishing process of 0.925,0.800 and 0.720 silver alloys in a 0.07 vol.%ammonium sulphide solution for different immersion periods was analyzed by electrochemical impedance spectroscopy(EIS)and scanning electron microscopy(SEM).The polarisation curves showed that the copper content and sulphide increased the corrosion current density and delayed the passivation of silver alloys.The impedance spectra collected at the open circuit potential(OCP)showed a single capacitive,incomplete and depressed loop,indicating that the charge transfer resistance decreased as the copper content increased in the alloys.In contrast,the double-layer capacitance increased as the copper content increased.The SEM-EDS analysis confirmed that the copper-rich phase in the silver alloys was selectively dissolved due to the preference of S to react with Cu,resulting in a localised attack,thus delaying the formation of a passive film.A marked localised attack was observed in alloys with lower copper content.The mechanism for the tarnishing of silver alloys in sulphide media was dependent on the nature of the alloy and the greater affinity of copper for sulphur.The dissolution of Ag and Cu to form corrosion products was proposed as the rate determining step.展开更多
To study different corrosion resistances and surface film types of hexagonal close-packed(HCP)pure Mg and body-centered cubic(BCC)Mg−14wt.%Li alloy in 0.1 mol/L NaCl,a series of experiments were conducted,including hy...To study different corrosion resistances and surface film types of hexagonal close-packed(HCP)pure Mg and body-centered cubic(BCC)Mg−14wt.%Li alloy in 0.1 mol/L NaCl,a series of experiments were conducted,including hydrogen evolution,mass loss,in-situ electrochemical testing combined with Raman spectroscopy and microstructural observation.The results indicate that the corrosion resistance of pure Mg is superior to that of Mg−14Li,and the protective function of the surface films on both magnesium systems is elevated within 16 h of immersion in 0.1 mol/L NaCl.An articulated,thick,and needle-like surface film containing Li2CO3 on Mg−14Li,different from the typically thin,flaky Mg(OH)2 film on pure Mg,is confirmed via scanning electron microscopy(SEM).However,both surface films can be broken down at a high anodic over-potential.Thus,different corrosion resistances of the two Mg systems are ascribed to various protective films forming on their surfaces.展开更多
The alloy （AI-Cu-Mg） alloy important one dating back to the series （2xxx） where copper foundries basic element which represents the number （2）, the study relied on foundries add elements boron （B） and titanium...The alloy （AI-Cu-Mg） alloy important one dating back to the series （2xxx） where copper foundries basic element which represents the number （2）, the study relied on foundries add elements boron （B） and titanium （Ti） and then use a heat treatment （homogenizing process） to improve the corrosion resistance in saline （NaC1 3.5%） of the base alloy （A1-Cu-Mg）, was prepared four types of alloys （A, B, C, D） depending on the chemical composition. The results showed that the corrosion resistance in saline solution was the best resistance in the alloy （D） （A1-2% Cu-2% Mg-0.1% B-1.0% Ti） compared with the rest of bullion when an examination of corrosion of the alloy prepared after homogenizing. But by examining the surface roughness of the alloy ingot turned out that （D） is softer than the rest of the surface alloys and this is due to the addition of boron and titanium together increases surface smoothness in alloys because it works to reduce the grain size.展开更多
基金Project (SKL05011) supported by the Foundation of State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, China
文摘The corrosion resistance and mechanical properties were tested and compared for the newly synthesized as-cast,as-solution Ni-Cr-Mo-Cu corrosion resistant alloys and 1Cr18Ni9Ti austenitic stainless steel. Their valence electron structural units were constructed,and the relative parameters were calculated by means of the Empirical Electron theory of Solids and Molecules(EET). The results show that,during alloy elements Cr,Mo and Cu entering Ni-matrix,the bonding strength nA and bonding energy EA of the strongest bond of the alloy are greatly increased,causing the stronger solid solution strengthening effects(about 30% increase in σb). Also,as reinforcement of the main bond network and the improvement of stability of the alloy system due to the solution of these alloying elements in γ-Ni,the ionization of metal atoms in corrosion solution and the flow of electrons from anode to cathode would all be impeded during electro-chemical corrosion processes,which leads to the excellent corrosion resistant ability of the present Ni-Cr-Mo-Cu alloy(about 2-3 orders of magnitude as high as 1Cr18Ni9Ti austenitic stainless steel) in several highly aggressive solutions.
基金Projects(2016YFB0301001,2016YFB0301101)supported by the National Key Research and Development Program of ChinaProject(51801004)supported by the National Natural Science Foundation of China+1 种基金Project(KM201710005005)supported by Beijing Municipal Education Commission,ChinaProjects(2172013,2192006)supported by Beijing Natural Science Foundation,China
文摘An extruded Mg-4Zn-0.2Mn-0.2Ca alloy was developed as potential biodegradable bone-plate due to its excellent biocompatibility.Long term in vitro immersion in Hank’s solution and bending test were used to evaluate the degradability and the mechanical integrity of the alloy.The results revealed that the degradation rate of the bone-plate increased in the first 7 days and then decreased with the prolonged immersion time before it finally reached a steady stage(about 0.84 mm/a)after immersion for 90 days.The bending strength after immersion for 60 days was 67.6 MPa,indicating that the bone-plate could support certain mechanical load after long term degradation.The formation of corrosion pits after degradation stemmed from the separation of the continuously distributed second phases from Mg matrix under the action of micro-galvanic couples.As a result,the mechanical performance of Mg-4Zn-0.2Mn-0.2Ca alloy was aggravated owing to the corrosion holes on its surface.
基金Project (2002107) supported by the Natural Science Foundation of Hunan Province project(2005-241) supported by theScience Project of Changsha
文摘Compact anodic films with high hardness and good corrosion resistance on magnesium alloys were prepared by a new constant voltage and arc-free anodizing process. The effects of anodizing parameters such as applied voltage and electrolyte temperature on the peak current density and the thickness of films were investigated. In addition, the morphologies and corrosion resistance of films were investigated by scanning electron microscopy and potentiodynamic polarization, respectively. The results show that the higher the applied voltage, the higher the peak current density and the thicker the films. However, too high applied voltage may result in breakdown of films and intense sparking which may deteriorate the properties of the anodic films and bring about unsafety. The new anodizing process can be applied in a wide range of temperature. The new anodic films have numbers of pores with the diameter of 0.55.0μm which do not transverse the entire film.
基金Projects(cstc2019jcyj-msxmX0566,cstc2018jcyjAX0450,cstc2018jcyjA2923,cstc2017jcyjAX0393)supported by the Natural Science Foundation of Chongqing City,ChinaProject(2019CDXZWL002)supported by President Foundation of Chongqing University,China+2 种基金Projects(2019CDXYWL0029,2018CDJDWL0011)supported by Fundamental Research Funds for the Central Universities of ChinaProjects(KJKJQN201800102,KJQN201800619,KJ1703042)supported by Science and Technology Research Program of Chongqing Municipal Education Commission,ChinaProjects(202003150060,202003150078)supported by Sharing Fund of Large-scale Equipment of Chongqing University,China。
文摘The aspartic acid(ASP),an environment-friendly corrosion inhibitor,was explored to intercalate into the ZnAl-layered double hydroxide(ZnAl-LDH)and MgAl-LDH coatings on AZ31 magnesium alloys by a facile one-step hydrothermal method.The morphology,composition,structure and corrosion resistance of the prepared coatings were comparatively investigated.It is found that the uniform and dense layered nanosheet(NS)vertically grows on the substrate,and the MgAl−ASP-LDH films exhibit a three-dimensional(3D)rose-like sheet structure with high ratio of pore coverage.The MgAl−ASP-LDH coating exhibits better corrosion resistance and durability of longtime immersion than ZnAl−ASP-LDH coating.The corrosion current density of two coatings is two or three orders of magnitude lower than that of bare Mg alloy,indicating that ZnAl/MgAl-LDH films intercalated with organic ASP anions can significantly improve the corrosion resistance of Mg alloy.
基金financial supports from the Natural Science Foundation of Shandong Province,China(No.ZR2019MEE107)Shandong Jiaotong University“Climbing”Research Innovation Team Program,China(No.SDJTC1802)PhD Scientific Research Foundation of Shandong Jiaotong University,China(No.BS2018005)。
文摘Nickel-based superalloys with and without Co by partial replacement of W were prepared using double vacuum melting.A comparison of the oxidation in air and hot corrosion behaviors under molten 75 wt.%Na2 SO4+25 wt.%NaCl at 900℃were systematically investigated.The results showed that partial replacement of W with Co promoted the formation of chromia scale and consequently decreased the oxidation rate.Besides,the addition of Co also retarded the internal oxidation/nitridation of Al and consequently promoted the growth of Al_(2) O3 scale,which further decreased the scaling rate and improved the adhesion of scale.Moreover,the addition of Co also further improved the hot corrosion resistance under molten Na2 SO4-NaCl salts.
基金the financial supports from the Natural Science Foundation of Shanxi Province, China (201901D211310)the National Natural Science Foundation of China (52071227)+2 种基金the Transformation of Scientific and Technological Achievements Programs of Higher Education Institutions in Shanxi, China (TSTAP)Science and Technology Major Projects of Shanxi Province, China (20191102004, 201903D111008)the Central Special Funds Guiding the Development of Local Science and Technology, China (YDZX20181400002967)
文摘To find suitable biodegradable materials for implant applications,Mg−6Zn−0.3Mn−xCa(x=0,0.2 and 0.5,wt.%)alloys were prepared by semi-continuous casting followed by hot-extrusion technique.The microstructure and mechanical properties of Mg−6Zn−0.3Mn−xCa alloys were investigated using the optical microscope,scanning electron microscope and tensile testing.Results indicated that minor Ca addition can slightly refine grains of the extruded Mg−6Zn−0.3Mn alloy and improve its strength.When 0.2 wt.%and 0.5 wt.%Ca were added,the grain sizes of the as-extruded alloys were refined from 4.8 to 4.6 and 4.2μm,respectively.Of the three alloys studied,the alloy with 0.5 wt.%Ca exhibits better combined mechanical properties with the ultimate tensile strength and elongation of 334 MPa and 20.3%.The corrosion behaviour,cell viability and antibacterial activities of alloys studied were also evaluated.Increasing Ca content deteriorates the corrosion resistance of alloys due to the increase of amount of effective cathodic sites caused by the formation of more Ca2Mg6Zn3 phases.Cytotoxicity evaluation with L929 cells shows higher cell viability of the Mg−6Zn−0.3Mn−0.5Ca alloy compared to Mg−6Zn−0.3Mn and Mg−6Zn−0.3Mn−0.2Ca alloys.The antibacterial activity against Staphylococcus aureus is enhanced with increasing the Ca content due to its physicochemical and biological performance in bone repairing process.
基金CONACyT for their support:scholarship to JOC 45653 and the Basic Science Projects 239938LANCIC CONACyT LN 232619,260779 and 271614the Chemistry School at UNAM for the financial support given for this work through the Program for Research and Graduate Studies Sponsorship(PAIP)
文摘Silver and silver alloys usually tarnish,which causes some changes in their aesthetic appearance and electrical properties,due to their exposure to sulphide environments(H2S),and this is a problem in the field of corrosion and conservation of cultural heritage metallic artefacts.In this study,the role of copper content in the tarnishing process of 0.925,0.800 and 0.720 silver alloys in a 0.07 vol.%ammonium sulphide solution for different immersion periods was analyzed by electrochemical impedance spectroscopy(EIS)and scanning electron microscopy(SEM).The polarisation curves showed that the copper content and sulphide increased the corrosion current density and delayed the passivation of silver alloys.The impedance spectra collected at the open circuit potential(OCP)showed a single capacitive,incomplete and depressed loop,indicating that the charge transfer resistance decreased as the copper content increased in the alloys.In contrast,the double-layer capacitance increased as the copper content increased.The SEM-EDS analysis confirmed that the copper-rich phase in the silver alloys was selectively dissolved due to the preference of S to react with Cu,resulting in a localised attack,thus delaying the formation of a passive film.A marked localised attack was observed in alloys with lower copper content.The mechanism for the tarnishing of silver alloys in sulphide media was dependent on the nature of the alloy and the greater affinity of copper for sulphur.The dissolution of Ag and Cu to form corrosion products was proposed as the rate determining step.
基金Projects(51901047,51801029)supported by the National Natural Science Foundation of ChinaProjects(201911845185,xj201911845345)supported by the National College Students Innovation and Entrepreneurship Training Program,China。
文摘To study different corrosion resistances and surface film types of hexagonal close-packed(HCP)pure Mg and body-centered cubic(BCC)Mg−14wt.%Li alloy in 0.1 mol/L NaCl,a series of experiments were conducted,including hydrogen evolution,mass loss,in-situ electrochemical testing combined with Raman spectroscopy and microstructural observation.The results indicate that the corrosion resistance of pure Mg is superior to that of Mg−14Li,and the protective function of the surface films on both magnesium systems is elevated within 16 h of immersion in 0.1 mol/L NaCl.An articulated,thick,and needle-like surface film containing Li2CO3 on Mg−14Li,different from the typically thin,flaky Mg(OH)2 film on pure Mg,is confirmed via scanning electron microscopy(SEM).However,both surface films can be broken down at a high anodic over-potential.Thus,different corrosion resistances of the two Mg systems are ascribed to various protective films forming on their surfaces.
文摘The alloy （AI-Cu-Mg） alloy important one dating back to the series （2xxx） where copper foundries basic element which represents the number （2）, the study relied on foundries add elements boron （B） and titanium （Ti） and then use a heat treatment （homogenizing process） to improve the corrosion resistance in saline （NaC1 3.5%） of the base alloy （A1-Cu-Mg）, was prepared four types of alloys （A, B, C, D） depending on the chemical composition. The results showed that the corrosion resistance in saline solution was the best resistance in the alloy （D） （A1-2% Cu-2% Mg-0.1% B-1.0% Ti） compared with the rest of bullion when an examination of corrosion of the alloy prepared after homogenizing. But by examining the surface roughness of the alloy ingot turned out that （D） is softer than the rest of the surface alloys and this is due to the addition of boron and titanium together increases surface smoothness in alloys because it works to reduce the grain size.
