Vacuum brazing of TiAl alloy to 40Cr steel sheets was conducted with newly developed CuTiNiZrV amorphous foils. It was found that a diffusion layer,filler metal and reaction layer existed in the brazed seam. The diffu...Vacuum brazing of TiAl alloy to 40Cr steel sheets was conducted with newly developed CuTiNiZrV amorphous foils. It was found that a diffusion layer,filler metal and reaction layer existed in the brazed seam. The diffusion layer in the joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25(at.%) foil was flat and thin,containing Ti19Al6 and Ti2Cu intermetallic compounds; however,the diffusion layer brazed with Cu37.5Ti25Ni12.5Zr12.5V12.5 foil was uneven with bulges,consisting of essentially Ti-based solute solution. The foil with 12.5 at.% V showed inferior spreadability compared to that with 6.25 at.% V at brazing temperature. However,fracture happened along the diffusion layer with 6.25 at.% V foil due to the formation of brittle intermetallic phases,but the joints brazed with 12.5 at.% V foil failed through the TiAl substrate. These results show that designing amorphous alloy with less Ti and more V for brazing TiAl alloy to steel is appropriate.展开更多
Dissimilar metal joining of Ti-6AI-4V （TC4） titanium alloy to as-rolled 40Cr steel rods was conducted with friction welding, and the effect of post-weld heat treatment （PWHT） on the microstructure and mechanical p...Dissimilar metal joining of Ti-6AI-4V （TC4） titanium alloy to as-rolled 40Cr steel rods was conducted with friction welding, and the effect of post-weld heat treatment （PWHT） on the microstructure and mechanical properties of the resultant joints was investigated. The average tensile strength of the as-welded joints reached 766 MPa and failure occurred in 40Cr steel base metal. However, after PWHT at 600℃ for 0.5, 1, 2 and 3 h, the tensile strength of the joints decreased and fracture happened through the interface with quasi-cleavage features. The bending angle of specimens was improved from 9.6° in as-welded state to 32.5° after PWHT for 2 h. The tensile strength of the joint was enhanced by martensitic transformation near the interface in as-welded state. Sorbite formed near the interface in PWHT state and improved the bending ductility of the joint. TiC brittle phase formed at the interface after PWHT for 0.5 h and deteriorated the tensile strength and bending ductility of the joint. After PWHT for 2 h, no TiC phase was detected at the interface. The microhardness on the interface in as-welded state was higher than that after PWHT, indicating that the decrease of microhardness around the interface could be accompanied by degradation of tensile strength but improvement of bending ductility of the joints.展开更多
It has theoretical significance and practical value to synthetize and modify amorphous carbon films by liquid electro-deposition technique due to its low cost, simple equipment, and better operability in uniform depos...It has theoretical significance and practical value to synthetize and modify amorphous carbon films by liquid electro-deposition technique due to its low cost, simple equipment, and better operability in uniform deposition of the films with large-area and complex shape work pieces. This article introduces the research situation of the carbon films prepared by liquid phase electrochemical deposition according to the applied voltage, discusses the influence of experimental parameters on the film properties, and describes possible reaction mechanisms. It summarizes the research progress of amorphous carbon films doped with metal and nonmetals. Finally, existing problems have been demonstrated and suggestions on research hotspots in the future are given.展开更多
基金financially supported by the State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology,Harbin,Chinathe National Natural Science Foundation of China (Grant No.51374048)+1 种基金the National Basic Research Program of China ("973 Program",Grant No.2011CB013402)the Fundamental Research Funds for the Central Universities
文摘Vacuum brazing of TiAl alloy to 40Cr steel sheets was conducted with newly developed CuTiNiZrV amorphous foils. It was found that a diffusion layer,filler metal and reaction layer existed in the brazed seam. The diffusion layer in the joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25(at.%) foil was flat and thin,containing Ti19Al6 and Ti2Cu intermetallic compounds; however,the diffusion layer brazed with Cu37.5Ti25Ni12.5Zr12.5V12.5 foil was uneven with bulges,consisting of essentially Ti-based solute solution. The foil with 12.5 at.% V showed inferior spreadability compared to that with 6.25 at.% V at brazing temperature. However,fracture happened along the diffusion layer with 6.25 at.% V foil due to the formation of brittle intermetallic phases,but the joints brazed with 12.5 at.% V foil failed through the TiAl substrate. These results show that designing amorphous alloy with less Ti and more V for brazing TiAl alloy to steel is appropriate.
基金financially supported by the National Natural Science Foundation of China (Grant No. 51374048)the National Basic Research Program of China ("973 Program", Grant No. 2011CB013402)+1 种基金the Fundamental Research Funds for the Central Universities (DUT13ZD209)the State Key Laboratory of Advanced Welding and Joining (AWJ-M14-06), Harbin Institute of Technology, Harbin, China
文摘Dissimilar metal joining of Ti-6AI-4V （TC4） titanium alloy to as-rolled 40Cr steel rods was conducted with friction welding, and the effect of post-weld heat treatment （PWHT） on the microstructure and mechanical properties of the resultant joints was investigated. The average tensile strength of the as-welded joints reached 766 MPa and failure occurred in 40Cr steel base metal. However, after PWHT at 600℃ for 0.5, 1, 2 and 3 h, the tensile strength of the joints decreased and fracture happened through the interface with quasi-cleavage features. The bending angle of specimens was improved from 9.6° in as-welded state to 32.5° after PWHT for 2 h. The tensile strength of the joint was enhanced by martensitic transformation near the interface in as-welded state. Sorbite formed near the interface in PWHT state and improved the bending ductility of the joint. TiC brittle phase formed at the interface after PWHT for 0.5 h and deteriorated the tensile strength and bending ductility of the joint. After PWHT for 2 h, no TiC phase was detected at the interface. The microhardness on the interface in as-welded state was higher than that after PWHT, indicating that the decrease of microhardness around the interface could be accompanied by degradation of tensile strength but improvement of bending ductility of the joints.
文摘It has theoretical significance and practical value to synthetize and modify amorphous carbon films by liquid electro-deposition technique due to its low cost, simple equipment, and better operability in uniform deposition of the films with large-area and complex shape work pieces. This article introduces the research situation of the carbon films prepared by liquid phase electrochemical deposition according to the applied voltage, discusses the influence of experimental parameters on the film properties, and describes possible reaction mechanisms. It summarizes the research progress of amorphous carbon films doped with metal and nonmetals. Finally, existing problems have been demonstrated and suggestions on research hotspots in the future are given.
