Ti coating on A3 steel was successfully prepared by direct electrochemical reduction of high-velocity oxy-fuel （HVOF） thermally sprayed and room-temperature dip-coating titanium dioxide coating on A3 steel in molten...Ti coating on A3 steel was successfully prepared by direct electrochemical reduction of high-velocity oxy-fuel （HVOF） thermally sprayed and room-temperature dip-coating titanium dioxide coating on A3 steel in molten CaCl2 at 850 ℃. The interfacial microstructure and mutual diffusion between coating and steel substrate were investigated using scanning electron microscopy （SEM） and energy dispersive X-ray （EDX） spectroscopy. The results show that the precursory TiO2 coating prepared by HVOF has closer contact and better adhesion with the A3 steel substrate. After electrolysis, all of the electro-generated Ti coatings show intact contact with the substrates, regardless of the original contact situation between TiO2 layer and the steel substrate in the precursors. The inter-diffusion between the iron substrate and the reduced titanium takes place at the interface. The results demonstrate the possibility of the surface electrochemical metallurgy （SECM） is a promising surface engineering and additive manufacturing method.展开更多
Joining in the semisolid state is considered a possible method to join alloys to each other. The mechanisms taking part in semisolid stir welding of AZ91 alloys were investigated. Two 7.5 mm-thick AZ91 pieces and a 2 ...Joining in the semisolid state is considered a possible method to join alloys to each other. The mechanisms taking part in semisolid stir welding of AZ91 alloys were investigated. Two 7.5 mm-thick AZ91 pieces and a 2 ram-thick Mg-25%Zn interlayer piece were placed in a heating plate. After holding for 3 min at a desired temperature, the weld seam was stirred by a rotational tool. The heating plate was travelled on a trolley at a constant speed of 4.6 cm/min. In addition, one sample was welded without interlayer. Evolution of welding as a function of stirring rate, tool shape and temperature was studied throughout this welding process with scanning electron and optical microscopes. Interlayer decreases the joining temperature and assists to investigate the possible semisolid stir welding mechanisms. Increasing temperature and stirring rate, and using round stirrer instead of grooved stirrer increase the stir zone width. The results show that some possible mechanisms are helpful to achieve a proper metallurgical bonding in the welding process, such as oxide layer disruption, liquid phase blending, globule joining, and liquid penetration to the base metal, merging a group of globule into stir zone from the base metal.展开更多
基金Projects(51071112,51325102)supported by the National Natural Science Foundation of China
文摘Ti coating on A3 steel was successfully prepared by direct electrochemical reduction of high-velocity oxy-fuel （HVOF） thermally sprayed and room-temperature dip-coating titanium dioxide coating on A3 steel in molten CaCl2 at 850 ℃. The interfacial microstructure and mutual diffusion between coating and steel substrate were investigated using scanning electron microscopy （SEM） and energy dispersive X-ray （EDX） spectroscopy. The results show that the precursory TiO2 coating prepared by HVOF has closer contact and better adhesion with the A3 steel substrate. After electrolysis, all of the electro-generated Ti coatings show intact contact with the substrates, regardless of the original contact situation between TiO2 layer and the steel substrate in the precursors. The inter-diffusion between the iron substrate and the reduced titanium takes place at the interface. The results demonstrate the possibility of the surface electrochemical metallurgy （SECM） is a promising surface engineering and additive manufacturing method.
文摘Joining in the semisolid state is considered a possible method to join alloys to each other. The mechanisms taking part in semisolid stir welding of AZ91 alloys were investigated. Two 7.5 mm-thick AZ91 pieces and a 2 ram-thick Mg-25%Zn interlayer piece were placed in a heating plate. After holding for 3 min at a desired temperature, the weld seam was stirred by a rotational tool. The heating plate was travelled on a trolley at a constant speed of 4.6 cm/min. In addition, one sample was welded without interlayer. Evolution of welding as a function of stirring rate, tool shape and temperature was studied throughout this welding process with scanning electron and optical microscopes. Interlayer decreases the joining temperature and assists to investigate the possible semisolid stir welding mechanisms. Increasing temperature and stirring rate, and using round stirrer instead of grooved stirrer increase the stir zone width. The results show that some possible mechanisms are helpful to achieve a proper metallurgical bonding in the welding process, such as oxide layer disruption, liquid phase blending, globule joining, and liquid penetration to the base metal, merging a group of globule into stir zone from the base metal.
