Stitch welding of plate covered skeleton structure of Ti-6Al-4V titanium alloys has a variety of applications in aerospace vehicle manufacture. The laser stitch welding of Ti-6Al-4V titanium alloys was carried out by ...Stitch welding of plate covered skeleton structure of Ti-6Al-4V titanium alloys has a variety of applications in aerospace vehicle manufacture. The laser stitch welding of Ti-6Al-4V titanium alloys was carried out by a 4 kW ROFIN fiber laser. Influences of laser welding parameters on the macroscopic geometry, porosity, microstructure and mechanical properties of the stitch welded seams were investigated by digital microscope, optical microscope, scanning electron microscope and universal tensile testing machine. The results showed that the three-pipe nozzle with gas flow rate larger than 5 L/min could avoid oxidization, presenting better shielding effect in comparison with the single-pipe nozzle. Porosity formation could be suppressed with the gap between plate and skeleton less than 0.1 mm, while the existing porosity can be reduced with remelting. The maximum shear strength of stitch welding joint with minimal porosity was obtained by employing laser power of 1700 W, welding speed of 1.5 m/min and defocusing distance of ＋8 ram.展开更多
The corrosion and tribocorrosion behaviors of AISI 316 stainless steel and Ti6Al4V alloys sliding against Al2O3 in artificial seawater using a pin-on-disk test rig were investigated. And the synergistic effect between...The corrosion and tribocorrosion behaviors of AISI 316 stainless steel and Ti6Al4V alloys sliding against Al2O3 in artificial seawater using a pin-on-disk test rig were investigated. And the synergistic effect between corrosion and wear was emphatically evaluated. The results show that the open circuit potentials of both alloys drop down to more negative value due to friction. The corrosion current densities obtained under tribocorrosion condition are much higher than those under corrosion-only condition. Friction obviously accelerates the corrosion of the alloys. The wear loss for both alloys is larger in seawater than that in pure water. Wear loss is obviously accelerated by corrosion. And AISI 316 stainless steel is less resistant to sliding damage than Ti6Al4V alloy. The synergistic effect between wear and corrosion is a significant factor for the materials loss in tribocorrosion. In this surface-on-surface contact geometry friction system, the material loss is large but the ratio of wear-accelerated-corrosion to the total wear loss is very low.展开更多
Three Ti-6Al-4V alloy powders with median diameters of 103, 66 and 44 pm, respectively, were pressed by high-velocity compaction （HVC） technology and then sintered in vacuum. The effects of particle sizes on forming...Three Ti-6Al-4V alloy powders with median diameters of 103, 66 and 44 pm, respectively, were pressed by high-velocity compaction （HVC） technology and then sintered in vacuum. The effects of particle sizes on forming as well as properties of sintered samples were investigated. The results show that fine powders are more difficult to press than coarse powders and its compact density is lower too. But the sintered density of fine powders is obviously higher than that of coarse powders. Compared with the powders with 103 and 66 ~un in diameter, the green density with 44 ~rn diameter powders is lower, which is 85.1% of theoretical density （TD） at an impact energy of 913 J. After sintering at 1300 ~C for 2,5 h, the sintered density of the compacts with 44 pm diameter powders is the highest, and reaches 98.2% of TD. Moreover, the sintered sample with 44 pan in diameter has the highest hardness and compressive strength, which are HV 354 and 1265 MPa, respectively.展开更多
Microstructure and texture evolution during hot compression of Ti6Al4 V alloy with an initial equiaxed microstructure were studied in the temperature range of 850-930 °C, strain rate range of 0.01-1 s-1 and engin...Microstructure and texture evolution during hot compression of Ti6Al4 V alloy with an initial equiaxed microstructure were studied in the temperature range of 850-930 °C, strain rate range of 0.01-1 s-1 and engineering compressive strain of 70%. The results indicate that when temperature is below 900 °C and strain rate is higher than 0.1 s-1, the microstructure is mainly composed of elongated α grains. While deforming at higher temperatures and lower strain rates, dynamic recrystallization takes place. Electron back scattered diffraction（EBSD） result shows that during dynamic recrystallization, subgrain boundaries absorb dislocations and the recrystallized grains with high angle grain boundary form. At 930 °C dynamic recrystallization has basically completed, and needlelike α phase forms after water quenching. Pole figure analysis indicates that compared with the initial specimen, textures below 930 °C are weaker, while at 930 °C they are stronger.展开更多
The Ti−6Al−4V(TC4)alloy powder and forged solid were diffusion bonded by hot isostatic pressing(HIP)to fabricate a powder−solid part.The microstructure of the powder−solid part was observed by scanning electron micros...The Ti−6Al−4V(TC4)alloy powder and forged solid were diffusion bonded by hot isostatic pressing(HIP)to fabricate a powder−solid part.The microstructure of the powder−solid part was observed by scanning electron microscope(SEM).The microhardness and tensile tests were conducted to investigate the mechanical properties.The results showed that the powder compact was near-fully dense,and the powder/solid interface was tight and complete.The microhardness of the interface was higher than that of the powder compact and solid.The fractures of all powder−solid tensile specimens were on the solid side rather than at the interface,which indicated that a good interfacial strength was obtained.The tensile strength and elongation of the powder compact were higher than those of the solid.It is concluded that the HIP process can successfully fabricate high-quality Ti−6Al−4V powder−solid parts,which provides a novel near net shape technology for titanium alloys.展开更多
Titanium(Ti)nitrides were in situ grown on Ti6Al4V alloy(TA)using a glow discharge plasma nitriding(GDPN).The morphology,chemical composition,phase and mechanical property of the obtained nitrided TA were analyzed usi...Titanium(Ti)nitrides were in situ grown on Ti6Al4V alloy(TA)using a glow discharge plasma nitriding(GDPN).The morphology,chemical composition,phase and mechanical property of the obtained nitrided TA were analyzed using a scanning electron microscope(SEM),energy dispersive spectroscope(EDS),X-ray diffraction(XRD),and nanoindentation tester,respectively.The tribological performances of un-nitrided and nitrided TAs were evaluated using a ball-on-plate wear tester,and the wear mechanism was also discussed in detail.The results show that the nitrided layer with the compound and diffusion layers is formed on the nitrided TA,which is composed of δ-TiN and a-Ti phases.The nanohardness and elastic modulus of nitrided TA are 6.05 and 143.13 GPa,respectively,higher than those of un-nitrided TA.The friction reduction and anti-wear performances of nitrided TA are better than those of un-nitrided TA,and the wear mechanism is primary abrasive wear,accompanying with adhesive wear,which is attributed to the formation of Ti nitrides with the high nanohardness and elastic modulus.展开更多
Dear Editor,We read with great interest the article by Tan et al.titled“Accelerated fracture healing by osteogenic Ti45Nb implants through the PI3K-Akt signaling pathway”[1].This research thoroughly examines the bon...Dear Editor,We read with great interest the article by Tan et al.titled“Accelerated fracture healing by osteogenic Ti45Nb implants through the PI3K-Akt signaling pathway”[1].This research thoroughly examines the bone-forming capabilities of the Ti45Nb alloy.The in vitro studies revealed that the Ti45Nb alloy enhances the osteogenic differentiation of MC3T3-E1 cells more effectively than Ti6Al4V alloy controls,showing no noticeable cytotoxic effects.展开更多
基金Project(2012BAF08B02)supported by Key Project in the National Science and Technology Pillar Program During the Twelfth Five-year Plan Period,China
文摘Stitch welding of plate covered skeleton structure of Ti-6Al-4V titanium alloys has a variety of applications in aerospace vehicle manufacture. The laser stitch welding of Ti-6Al-4V titanium alloys was carried out by a 4 kW ROFIN fiber laser. Influences of laser welding parameters on the macroscopic geometry, porosity, microstructure and mechanical properties of the stitch welded seams were investigated by digital microscope, optical microscope, scanning electron microscope and universal tensile testing machine. The results showed that the three-pipe nozzle with gas flow rate larger than 5 L/min could avoid oxidization, presenting better shielding effect in comparison with the single-pipe nozzle. Porosity formation could be suppressed with the gap between plate and skeleton less than 0.1 mm, while the existing porosity can be reduced with remelting. The maximum shear strength of stitch welding joint with minimal porosity was obtained by employing laser power of 1700 W, welding speed of 1.5 m/min and defocusing distance of ＋8 ram.
基金supported by the National Natural Science Foundation of China(No.51505323)the Applied Basic Research Program of Shanxi Province,China(Nos.20210302123117,20210302124658).
基金Project (LSL-1310) supported by the Open Project of State Key Laboratory of Solid Lubrication,Collaborative Innovation Center of Nonferrous Metals of Henan Province,ChinaProject (51171059) supported by the National Natural Science Foundation of China
文摘The corrosion and tribocorrosion behaviors of AISI 316 stainless steel and Ti6Al4V alloys sliding against Al2O3 in artificial seawater using a pin-on-disk test rig were investigated. And the synergistic effect between corrosion and wear was emphatically evaluated. The results show that the open circuit potentials of both alloys drop down to more negative value due to friction. The corrosion current densities obtained under tribocorrosion condition are much higher than those under corrosion-only condition. Friction obviously accelerates the corrosion of the alloys. The wear loss for both alloys is larger in seawater than that in pure water. Wear loss is obviously accelerated by corrosion. And AISI 316 stainless steel is less resistant to sliding damage than Ti6Al4V alloy. The synergistic effect between wear and corrosion is a significant factor for the materials loss in tribocorrosion. In this surface-on-surface contact geometry friction system, the material loss is large but the ratio of wear-accelerated-corrosion to the total wear loss is very low.
基金Project (51004040) supported by the National Natural Science Foundation of ChinaProject (20110952K) supported by Open Research Fund of State Key Laboratory of Powder Metallurgy of Central South University, China
文摘Three Ti-6Al-4V alloy powders with median diameters of 103, 66 and 44 pm, respectively, were pressed by high-velocity compaction （HVC） technology and then sintered in vacuum. The effects of particle sizes on forming as well as properties of sintered samples were investigated. The results show that fine powders are more difficult to press than coarse powders and its compact density is lower too. But the sintered density of fine powders is obviously higher than that of coarse powders. Compared with the powders with 103 and 66 ~un in diameter, the green density with 44 ~rn diameter powders is lower, which is 85.1% of theoretical density （TD） at an impact energy of 913 J. After sintering at 1300 ~C for 2,5 h, the sintered density of the compacts with 44 pm diameter powders is the highest, and reaches 98.2% of TD. Moreover, the sintered sample with 44 pan in diameter has the highest hardness and compressive strength, which are HV 354 and 1265 MPa, respectively.
基金Projects(51071122,51271147)supported by the National Natural Science Foundation of ChinaProject(B08040)supported by Program of Introducing Talents of Discipline to Universities("111"Project),China
文摘Microstructure and texture evolution during hot compression of Ti6Al4 V alloy with an initial equiaxed microstructure were studied in the temperature range of 850-930 °C, strain rate range of 0.01-1 s-1 and engineering compressive strain of 70%. The results indicate that when temperature is below 900 °C and strain rate is higher than 0.1 s-1, the microstructure is mainly composed of elongated α grains. While deforming at higher temperatures and lower strain rates, dynamic recrystallization takes place. Electron back scattered diffraction（EBSD） result shows that during dynamic recrystallization, subgrain boundaries absorb dislocations and the recrystallized grains with high angle grain boundary form. At 930 °C dynamic recrystallization has basically completed, and needlelike α phase forms after water quenching. Pole figure analysis indicates that compared with the initial specimen, textures below 930 °C are weaker, while at 930 °C they are stronger.
基金the National Natural Science Foundation of China(No.51675029).
文摘The Ti−6Al−4V(TC4)alloy powder and forged solid were diffusion bonded by hot isostatic pressing(HIP)to fabricate a powder−solid part.The microstructure of the powder−solid part was observed by scanning electron microscope(SEM).The microhardness and tensile tests were conducted to investigate the mechanical properties.The results showed that the powder compact was near-fully dense,and the powder/solid interface was tight and complete.The microhardness of the interface was higher than that of the powder compact and solid.The fractures of all powder−solid tensile specimens were on the solid side rather than at the interface,which indicated that a good interfacial strength was obtained.The tensile strength and elongation of the powder compact were higher than those of the solid.It is concluded that the HIP process can successfully fabricate high-quality Ti−6Al−4V powder−solid parts,which provides a novel near net shape technology for titanium alloys.
基金Funded by the Fundamental Research Funds for the Central Universities(Nos.2232018A3-08,2232018D3-04)
文摘Titanium(Ti)nitrides were in situ grown on Ti6Al4V alloy(TA)using a glow discharge plasma nitriding(GDPN).The morphology,chemical composition,phase and mechanical property of the obtained nitrided TA were analyzed using a scanning electron microscope(SEM),energy dispersive spectroscope(EDS),X-ray diffraction(XRD),and nanoindentation tester,respectively.The tribological performances of un-nitrided and nitrided TAs were evaluated using a ball-on-plate wear tester,and the wear mechanism was also discussed in detail.The results show that the nitrided layer with the compound and diffusion layers is formed on the nitrided TA,which is composed of δ-TiN and a-Ti phases.The nanohardness and elastic modulus of nitrided TA are 6.05 and 143.13 GPa,respectively,higher than those of un-nitrided TA.The friction reduction and anti-wear performances of nitrided TA are better than those of un-nitrided TA,and the wear mechanism is primary abrasive wear,accompanying with adhesive wear,which is attributed to the formation of Ti nitrides with the high nanohardness and elastic modulus.
文摘Dear Editor,We read with great interest the article by Tan et al.titled“Accelerated fracture healing by osteogenic Ti45Nb implants through the PI3K-Akt signaling pathway”[1].This research thoroughly examines the bone-forming capabilities of the Ti45Nb alloy.The in vitro studies revealed that the Ti45Nb alloy enhances the osteogenic differentiation of MC3T3-E1 cells more effectively than Ti6Al4V alloy controls,showing no noticeable cytotoxic effects.
