In many circumstances,dissimilar metals have to be bonded together and the resulting joint interfaces must typically sustain mechanical and/or electrical forces without failure,which is not possible by fusion welding ...In many circumstances,dissimilar metals have to be bonded together and the resulting joint interfaces must typically sustain mechanical and/or electrical forces without failure,which is not possible by fusion welding processes.The melting points of magnesium(Mg)and copper(Cu)have a significant difference(nearly 400℃)and this may lead to a large difference in the microstructure and joint performance of Mg-Cu joints.However,diffusion bonding can be used to join these alloys without much difficulty.This work analyses the effect of parameters on diffusion layer thickness,hardness and strength of magnesium-copper dissimilar joints.The experiments were conducted using three-factor,five-level,central composite rotatable design matrix.Empirical relationships were developed to predict diffusion layer thickness,hardness and strength using response surface methodology.It is found that bonding temperature has predominant effect on bond characteristics.Joints fabricated at a bonding temperature of 450℃, bonding pressure of 12 MPa and bonding time of 30 min exhibited maximum shear strength and bonding strength of 66 and 81 MPa, respectively.展开更多
The effects of chloride and thiosulfate ions on localized corrosion of alloy 800 are investigated through dynamical observation of the change in phase image of the diffusion layer during passive film breakdown using d...The effects of chloride and thiosulfate ions on localized corrosion of alloy 800 are investigated through dynamical observation of the change in phase image of the diffusion layer during passive film breakdown using digital holography. The results indicate that solution chemistry has a significant effect on film breakdown and diffusion layer. The phase distribution changes at different applied potentials show that in the process of film breakdown, dissolution of metal ions from pitting is not remarkable in chloride-only solution, whereas dissolution of metal ions is significantly high in thiosulfate and chloride solution. Thiosulfate has a combined effect with chloride ions in passive film degradation.展开更多
Aluminum was deposited by diffusion into Cu-Al-Y alloy substrates by the pack-cementation process.Diffusion was carried out in two kinds of container with pot-type and can-type,and the results are presented.The effect...Aluminum was deposited by diffusion into Cu-Al-Y alloy substrates by the pack-cementation process.Diffusion was carried out in two kinds of container with pot-type and can-type,and the results are presented.The effects of various time and temperature on the coating characteristics of Cu-Al-Y was also investigated.The result shows that the diffusion layer is nearly 170-200μm in thickness by aluminizing treatment at 900-950℃for 6-8 h in pot-type container.The aluminized layers were observed by a scanning electron micrograph(SEM),we can found:A uniform coating was achieved on Cu-Al-Y alloy surface,relatively uniform thickness and even interfaces between the layers and the substrate.The diffusion coefficient of Al in Cu-Al-Y alloys at 900℃in pot-type container can be calculated is 3.65×10-12 m 2 /s.展开更多
基金support rendered through a Major Research Project No. F-31-51/2005(SR)
文摘In many circumstances,dissimilar metals have to be bonded together and the resulting joint interfaces must typically sustain mechanical and/or electrical forces without failure,which is not possible by fusion welding processes.The melting points of magnesium(Mg)and copper(Cu)have a significant difference(nearly 400℃)and this may lead to a large difference in the microstructure and joint performance of Mg-Cu joints.However,diffusion bonding can be used to join these alloys without much difficulty.This work analyses the effect of parameters on diffusion layer thickness,hardness and strength of magnesium-copper dissimilar joints.The experiments were conducted using three-factor,five-level,central composite rotatable design matrix.Empirical relationships were developed to predict diffusion layer thickness,hardness and strength using response surface methodology.It is found that bonding temperature has predominant effect on bond characteristics.Joints fabricated at a bonding temperature of 450℃, bonding pressure of 12 MPa and bonding time of 30 min exhibited maximum shear strength and bonding strength of 66 and 81 MPa, respectively.
基金supported by Natural Sciences and Engineering Research Council of Canada Discovery GrantNational Natural Science Foundation of China (No. 51371124)
文摘The effects of chloride and thiosulfate ions on localized corrosion of alloy 800 are investigated through dynamical observation of the change in phase image of the diffusion layer during passive film breakdown using digital holography. The results indicate that solution chemistry has a significant effect on film breakdown and diffusion layer. The phase distribution changes at different applied potentials show that in the process of film breakdown, dissolution of metal ions from pitting is not remarkable in chloride-only solution, whereas dissolution of metal ions is significantly high in thiosulfate and chloride solution. Thiosulfate has a combined effect with chloride ions in passive film degradation.
基金Basic Research Priorities Program of the Science and Technology Committee of Shanghai(03JC14063)Shanghai Leading Academic Discipline Project(J50503)Innovative Program of the Education Commission of Shanghai(11YZ112)
文摘Aluminum was deposited by diffusion into Cu-Al-Y alloy substrates by the pack-cementation process.Diffusion was carried out in two kinds of container with pot-type and can-type,and the results are presented.The effects of various time and temperature on the coating characteristics of Cu-Al-Y was also investigated.The result shows that the diffusion layer is nearly 170-200μm in thickness by aluminizing treatment at 900-950℃for 6-8 h in pot-type container.The aluminized layers were observed by a scanning electron micrograph(SEM),we can found:A uniform coating was achieved on Cu-Al-Y alloy surface,relatively uniform thickness and even interfaces between the layers and the substrate.The diffusion coefficient of Al in Cu-Al-Y alloys at 900℃in pot-type container can be calculated is 3.65×10-12 m 2 /s.
