Magnetron-sputter deposition was used to produce Ti-48Al-8Cr-2Ag coating on a cast alloy substrate with the same composition. Hot corrosion was carried out in molten (Na,K)2SO4 and Na2SO4+NaCl at 900 ℃. The sputtered...Magnetron-sputter deposition was used to produce Ti-48Al-8Cr-2Ag coating on a cast alloy substrate with the same composition. Hot corrosion was carried out in molten (Na,K)2SO4 and Na2SO4+NaCl at 900 ℃. The sputtered nanocrystalline coating shows much better hot-corrosion resistance in molten (Na,K)2SO4 as a result of the formation of a continuous and compact Al2O3 scale. The nanocrystallization of TiAlCrAg alloy prolongs the incubation of breakaway corrosion and improves the hot-corrosion resistance of TiAlCrAg alloy in molten Na2SO4+NaCl. The relevant corrosion mechanism was discussed.展开更多
The microstructures of the siliconized specimens of Ti-48Al alloy were analyzed by SEM equipped with XEDS. The specimens were pack siliconized with the two different cementations, 15%Si+85% A12O3 and 15%Si+85%ZrO2. Th...The microstructures of the siliconized specimens of Ti-48Al alloy were analyzed by SEM equipped with XEDS. The specimens were pack siliconized with the two different cementations, 15%Si+85% A12O3 and 15%Si+85%ZrO2. The results show that a composite siliconized layer is formed on the surface of the TiAl alloy. The outer layer is the continuous A12O3 where a lot of Si particles adhered; the inner layer is most of Ti5Si3 with amount of ALjOs particles dispersed in. It was deduced that the A12O3 in the cementation layer is formed by the Al atoms in the TiAl substrate react with the residual O in the furnace and in the TiAl substrate.展开更多
The effects of lamellar structure on deformation and fracture behavior in a Ti 48Al 2Mn 2Nb alloy produced by centrifugal spray deposition(CSD) were investigated. The deformation and fracture of samples after tensile ...The effects of lamellar structure on deformation and fracture behavior in a Ti 48Al 2Mn 2Nb alloy produced by centrifugal spray deposition(CSD) were investigated. The deformation and fracture of samples after tensile and compressive tests were examined in a scanning electron microscope (SEM). The in situ tensile testing was further carried out in a SEM and the crack growth path of samples was observed. The result shows that there is a remarkable effect of lamellar structure of CSD TiAl alloy on its deformation and fracture process. Especially, the main crack extension is dependent on the lamellar direction relative to tensile loading axis. SEM observations indicate that there is a shielding toughening effect of lamellar structure on fracture in CSD samples, such as, crack deflection, crack path tortuousity, and crack branching, etc. Moreover, the crack growth path shows that the main crack grows tortuously and uncontinuously by ligaments bridging many microcracks in front of crack tip. The effect mechanism of microstructure on deformation and fracture process is discussed.[展开更多
The effect of surface finish and annealing treatment on the oxidation behavior of Ti-48Al-8Cr-2Ag (molar fraction, %) alloy was investigated at 900 and 1 000 ℃, respectively in air. Thermal gravimetric analysis (TGA)...The effect of surface finish and annealing treatment on the oxidation behavior of Ti-48Al-8Cr-2Ag (molar fraction, %) alloy was investigated at 900 and 1 000 ℃, respectively in air. Thermal gravimetric analysis (TGA) was conducted for the characterization of oxidation kinetics. The microstructures of oxide scales were studied by scanning electron microscopy (SEM) and transmission election microscopy (TEM) techniques. Unfavorable effect of the annealing treatment on the oxidation behavior of the coating was also investigated. The results indicate that the oxidation behavior of the alloy is influenced by surface finish and annealing treatment. The oxidation rate of ground sample is lower than that of the polished alloy at 1 000 ℃ in air. The former forms a scale of merely Al2O3, and the latter forms a scale of the mixture of Al2O3 and TiO2. Annealing can improve the formation of TiO2.展开更多
基金Project(59971052) supported by the National Natural Science Foundation of China
文摘Magnetron-sputter deposition was used to produce Ti-48Al-8Cr-2Ag coating on a cast alloy substrate with the same composition. Hot corrosion was carried out in molten (Na,K)2SO4 and Na2SO4+NaCl at 900 ℃. The sputtered nanocrystalline coating shows much better hot-corrosion resistance in molten (Na,K)2SO4 as a result of the formation of a continuous and compact Al2O3 scale. The nanocrystallization of TiAlCrAg alloy prolongs the incubation of breakaway corrosion and improves the hot-corrosion resistance of TiAlCrAg alloy in molten Na2SO4+NaCl. The relevant corrosion mechanism was discussed.
基金supported by the National Natural Science Foundation of China(No.50171046)the Natural Science Foundation of Shanxi Province,China(No.20021051)
文摘The microstructures of the siliconized specimens of Ti-48Al alloy were analyzed by SEM equipped with XEDS. The specimens were pack siliconized with the two different cementations, 15%Si+85% A12O3 and 15%Si+85%ZrO2. The results show that a composite siliconized layer is formed on the surface of the TiAl alloy. The outer layer is the continuous A12O3 where a lot of Si particles adhered; the inner layer is most of Ti5Si3 with amount of ALjOs particles dispersed in. It was deduced that the A12O3 in the cementation layer is formed by the Al atoms in the TiAl substrate react with the residual O in the furnace and in the TiAl substrate.
基金Project (E990 0 0 7)supportedbyFujianProvincialNaturalScienceFoundation P .R .China
文摘The effects of lamellar structure on deformation and fracture behavior in a Ti 48Al 2Mn 2Nb alloy produced by centrifugal spray deposition(CSD) were investigated. The deformation and fracture of samples after tensile and compressive tests were examined in a scanning electron microscope (SEM). The in situ tensile testing was further carried out in a SEM and the crack growth path of samples was observed. The result shows that there is a remarkable effect of lamellar structure of CSD TiAl alloy on its deformation and fracture process. Especially, the main crack extension is dependent on the lamellar direction relative to tensile loading axis. SEM observations indicate that there is a shielding toughening effect of lamellar structure on fracture in CSD samples, such as, crack deflection, crack path tortuousity, and crack branching, etc. Moreover, the crack growth path shows that the main crack grows tortuously and uncontinuously by ligaments bridging many microcracks in front of crack tip. The effect mechanism of microstructure on deformation and fracture process is discussed.[
基金Project(2007430028) supported by the Science and Technique Foundation of Henan Educational Committee, China
文摘The effect of surface finish and annealing treatment on the oxidation behavior of Ti-48Al-8Cr-2Ag (molar fraction, %) alloy was investigated at 900 and 1 000 ℃, respectively in air. Thermal gravimetric analysis (TGA) was conducted for the characterization of oxidation kinetics. The microstructures of oxide scales were studied by scanning electron microscopy (SEM) and transmission election microscopy (TEM) techniques. Unfavorable effect of the annealing treatment on the oxidation behavior of the coating was also investigated. The results indicate that the oxidation behavior of the alloy is influenced by surface finish and annealing treatment. The oxidation rate of ground sample is lower than that of the polished alloy at 1 000 ℃ in air. The former forms a scale of merely Al2O3, and the latter forms a scale of the mixture of Al2O3 and TiO2. Annealing can improve the formation of TiO2.
