NIN has developed a new type of Ti alloy. It is suitable for structure pieces applied in hightemperature and high-pressure water/steam conditions. Its nominal composition is Ti-4Al-2V. In this paper, its microstructu...NIN has developed a new type of Ti alloy. It is suitable for structure pieces applied in hightemperature and high-pressure water/steam conditions. Its nominal composition is Ti-4Al-2V. In this paper, its microstructure, mechanical properties and corrosion resistance were studied in detail.展开更多
Four hydrogen contents were employed to investigate the effects of hydrogen on fatigue life of Ti 4Al 2V titanium alloy by means of section varied samples. Results reveal that the fatigue life of the materials with (...Four hydrogen contents were employed to investigate the effects of hydrogen on fatigue life of Ti 4Al 2V titanium alloy by means of section varied samples. Results reveal that the fatigue life of the materials with (116～280)×10 -6 hydrogen is higher than that of natural hydrogen material provided that the fatigue load Δ σ is over 550 MPa. At higher Δ σ , the content of hydrogen has small effects on fatigue life within (116280)×10 -6 hydrogen. For material containing 280×10 -6 hydrogen, fatigue cracks tend to initiate at sample edges at higher load, in contrast, to initiate at sites of hydrides at lower load. The interstitial hydrogen atoms softening the persistent slip bands(PSB) and hydrides separating from the body become the cause of decrease in fatigue life. Hydrides resolved into the body is observed at lower Δ σ for material with 280×10 -6 hydrogen, which is the result of concentration of hydrogen atoms at crack tips and stress induced re precipitation of hydrides.展开更多
The stripe cracks which formed along rolling direction on the surface of Ti–4Al–2V alloy cold-rolled sheet were observed by stereoscope, scanning electron microscope（SEM）, and energy-dispersive spectrometer（EDS）...The stripe cracks which formed along rolling direction on the surface of Ti–4Al–2V alloy cold-rolled sheet were observed by stereoscope, scanning electron microscope（SEM）, and energy-dispersive spectrometer（EDS）. Morphology analysis indicates that cracks are dominantly in zigzag shape, with 10–30 mm in length and less than 10 lm in depth, and there is no evidence of crack tips. Chemical composition analysis shows that crack regions feather high oxygen concentration while smooth surface is at normal oxygen level. It is obvious that the occurrence of strip cracks is mainly related to residual oxide on the surface of Ti–4Al–2V alloy cold-rolled sheet.展开更多
In this study, the effect of thermal oxidation on the lattice parameters of Ti-4Al-2V alloy was studied.Samples were oxidized at 450, 600 and 650 °C for 1-7 h in electric furnace under air atmosphere. The lattice...In this study, the effect of thermal oxidation on the lattice parameters of Ti-4Al-2V alloy was studied.Samples were oxidized at 450, 600 and 650 °C for 1-7 h in electric furnace under air atmosphere. The lattice parameters were determined using the Cohen method as a function of oxidation time at each temperature. The lattice parameters of as-received alloy are calculated as a = 0.29289 nm and c = 0.46652 nm. The thermal oxidation at 450 °C results in a gradual increase in a-parameter, whereas it goes through a maximum at higher temperatures（600 and 700 °C）. The results show that these maximums are reduced to an approximately constant value after a long-time oxidation. The c-parameter generally increases over the whole treatment condition. It is believed that these variations could be due to the dissolution of oxygen atoms in octahedral sites of hcp lattice of titanium.展开更多
文摘NIN has developed a new type of Ti alloy. It is suitable for structure pieces applied in hightemperature and high-pressure water/steam conditions. Its nominal composition is Ti-4Al-2V. In this paper, its microstructure, mechanical properties and corrosion resistance were studied in detail.
文摘Four hydrogen contents were employed to investigate the effects of hydrogen on fatigue life of Ti 4Al 2V titanium alloy by means of section varied samples. Results reveal that the fatigue life of the materials with (116～280)×10 -6 hydrogen is higher than that of natural hydrogen material provided that the fatigue load Δ σ is over 550 MPa. At higher Δ σ , the content of hydrogen has small effects on fatigue life within (116280)×10 -6 hydrogen. For material containing 280×10 -6 hydrogen, fatigue cracks tend to initiate at sample edges at higher load, in contrast, to initiate at sites of hydrides at lower load. The interstitial hydrogen atoms softening the persistent slip bands(PSB) and hydrides separating from the body become the cause of decrease in fatigue life. Hydrides resolved into the body is observed at lower Δ σ for material with 280×10 -6 hydrogen, which is the result of concentration of hydrogen atoms at crack tips and stress induced re precipitation of hydrides.
基金financially supported by the Sichuan Provincial Key Technology R&D Program (No. 2013GZX0136)
文摘The stripe cracks which formed along rolling direction on the surface of Ti–4Al–2V alloy cold-rolled sheet were observed by stereoscope, scanning electron microscope（SEM）, and energy-dispersive spectrometer（EDS）. Morphology analysis indicates that cracks are dominantly in zigzag shape, with 10–30 mm in length and less than 10 lm in depth, and there is no evidence of crack tips. Chemical composition analysis shows that crack regions feather high oxygen concentration while smooth surface is at normal oxygen level. It is obvious that the occurrence of strip cracks is mainly related to residual oxide on the surface of Ti–4Al–2V alloy cold-rolled sheet.
基金the Sahand University of Technology,Tabriz,Iran,for the financial support and provision of laboratory facilities
文摘In this study, the effect of thermal oxidation on the lattice parameters of Ti-4Al-2V alloy was studied.Samples were oxidized at 450, 600 and 650 °C for 1-7 h in electric furnace under air atmosphere. The lattice parameters were determined using the Cohen method as a function of oxidation time at each temperature. The lattice parameters of as-received alloy are calculated as a = 0.29289 nm and c = 0.46652 nm. The thermal oxidation at 450 °C results in a gradual increase in a-parameter, whereas it goes through a maximum at higher temperatures（600 and 700 °C）. The results show that these maximums are reduced to an approximately constant value after a long-time oxidation. The c-parameter generally increases over the whole treatment condition. It is believed that these variations could be due to the dissolution of oxygen atoms in octahedral sites of hcp lattice of titanium.
