Corrosion-resistant and biocompatible films were fabricated on AZ91D Mg alloy substrates by varying their roughness levels using met-allographic preparation and subsequent hydrothermal procedures.The coated films comp...Corrosion-resistant and biocompatible films were fabricated on AZ91D Mg alloy substrates by varying their roughness levels using met-allographic preparation and subsequent hydrothermal procedures.The coated films comprised a mixed structure of Mg(OH)_(2)and Mg-Al layered double hydroxides(LDH)and exhibited excellent compactness.Coating film thickness increased with decreasing surface roughness.Corrosion resistance was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy.Metallographic pretreat-ment influenced the chemical activity of the Mg alloy surface and helped modulate the dissolution rate of the Mg_(17)Al_(12)phase during the hydrothermal procedure.With decreasing roughness of the Mg substrate,the Al^(3+)concentration gradually increased,accelerating the in-situ formation of the Mg(OH)_(2)/LDH composite coating and improving its crystallinity.A thick and dense Mg(OH)_(2)/LDH coating was synthesized on the Mg substrate with the least roughness,substantially improving the corrosion resistance of the AZ91D alloy.The lowest corrosion current density((5.73±2.75)×10^(−8)A·cm^(−2))was achieved,which was approximately three orders of magnitude less than that of bare AZ91D.Moreover,the coating demonstrated biocompatibility with no evident cytotoxicity,cellular damage,and hemolytic phenomena.This study provides an effective method for preparing coatings on Mg alloy surfaces with excellent corrosion resistance and biocompatibility.展开更多
Realizing improved strength in composite metallic materials remains a challenge using conventional welding and joining systems due to the generation and development of brittle intermetallic compounds caused by complex...Realizing improved strength in composite metallic materials remains a challenge using conventional welding and joining systems due to the generation and development of brittle intermetallic compounds caused by complex thermal profiles during solidification.Here,wire arc additive manufacturing(WAAM)process was used to fabricate a steel-nickel structural component,whose average tensile strength of 634 MPa significantly exceeded that of feedstock materials(steel,537 MPa and nickel,455 MPa),which has not been reported previously.The as-fabricated sample exhibited hierarchically structural heterogeneity due to the interweaving deposition strategy.The improved mechanical response during tensile testing was due to the inter-locking microstructure forming a strong bond at the interface and solid solutions strengthening from the intermixing of the Fe and Ni increased the interface strength,beyond the sum of parts.The research offers a new route for producing high-quality steel-nickel dissimilar structures and widens the design opportunities of monolithic components,with site-specific properties,for specific structural or functional applications.展开更多
Experiments were carried out with bypass-current MIG welding–brazing of magnesium alloy to galvanized steel to investigate the effect of heat input on the microstructure and mechanical properties of lap joints. Exper...Experiments were carried out with bypass-current MIG welding–brazing of magnesium alloy to galvanized steel to investigate the effect of heat input on the microstructure and mechanical properties of lap joints. Experimental results indicated that the joint efficiency tended to increase at first and then to reduce with the increase of heat input. The joint efficiency reached its maximum of about 70% when the heat input was 155 J/mm. The metallurgical bonding between magnesium alloy and steel was a thin continuous reaction layer, and the intermetallic compound layer consisted of Mg–Zn and slight Fe–Al phases. It is concluded that bypass-current MIG welding–brazing is a stable welding process, which can be used to achieve defect-free joining of magnesium alloy to steel with good weld appearances.展开更多
基金the financial support by the Natural Science Foundation of Ningxia(Grant no.2022AAC03099)the Key R&D Project of Ningxia(Grant no.2020BDE03012)。
文摘Corrosion-resistant and biocompatible films were fabricated on AZ91D Mg alloy substrates by varying their roughness levels using met-allographic preparation and subsequent hydrothermal procedures.The coated films comprised a mixed structure of Mg(OH)_(2)and Mg-Al layered double hydroxides(LDH)and exhibited excellent compactness.Coating film thickness increased with decreasing surface roughness.Corrosion resistance was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy.Metallographic pretreat-ment influenced the chemical activity of the Mg alloy surface and helped modulate the dissolution rate of the Mg_(17)Al_(12)phase during the hydrothermal procedure.With decreasing roughness of the Mg substrate,the Al^(3+)concentration gradually increased,accelerating the in-situ formation of the Mg(OH)_(2)/LDH composite coating and improving its crystallinity.A thick and dense Mg(OH)_(2)/LDH coating was synthesized on the Mg substrate with the least roughness,substantially improving the corrosion resistance of the AZ91D alloy.The lowest corrosion current density((5.73±2.75)×10^(−8)A·cm^(−2))was achieved,which was approximately three orders of magnitude less than that of bare AZ91D.Moreover,the coating demonstrated biocompatibility with no evident cytotoxicity,cellular damage,and hemolytic phenomena.This study provides an effective method for preparing coatings on Mg alloy surfaces with excellent corrosion resistance and biocompatibility.
基金carried out at the Welding Engineering Research Group,University of Wollongong,and it was supported by China Scholarship Council(No.201506680056)the National Natural Science Foundation of China(No.51805085)。
文摘Realizing improved strength in composite metallic materials remains a challenge using conventional welding and joining systems due to the generation and development of brittle intermetallic compounds caused by complex thermal profiles during solidification.Here,wire arc additive manufacturing(WAAM)process was used to fabricate a steel-nickel structural component,whose average tensile strength of 634 MPa significantly exceeded that of feedstock materials(steel,537 MPa and nickel,455 MPa),which has not been reported previously.The as-fabricated sample exhibited hierarchically structural heterogeneity due to the interweaving deposition strategy.The improved mechanical response during tensile testing was due to the inter-locking microstructure forming a strong bond at the interface and solid solutions strengthening from the intermixing of the Fe and Ni increased the interface strength,beyond the sum of parts.The research offers a new route for producing high-quality steel-nickel dissimilar structures and widens the design opportunities of monolithic components,with site-specific properties,for specific structural or functional applications.
基金financially supported by the National Natural Science Foundation of China(No.51005049)
文摘Experiments were carried out with bypass-current MIG welding–brazing of magnesium alloy to galvanized steel to investigate the effect of heat input on the microstructure and mechanical properties of lap joints. Experimental results indicated that the joint efficiency tended to increase at first and then to reduce with the increase of heat input. The joint efficiency reached its maximum of about 70% when the heat input was 155 J/mm. The metallurgical bonding between magnesium alloy and steel was a thin continuous reaction layer, and the intermetallic compound layer consisted of Mg–Zn and slight Fe–Al phases. It is concluded that bypass-current MIG welding–brazing is a stable welding process, which can be used to achieve defect-free joining of magnesium alloy to steel with good weld appearances.
