The microstructure and hardness of the stir zone （SZ） with different welding heat inputs were investigated for friction stir-welded 2024-T3 aluminum by transmission electron microscopy, differential scanning calorim...The microstructure and hardness of the stir zone （SZ） with different welding heat inputs were investigated for friction stir-welded 2024-T3 aluminum by transmission electron microscopy, differential scanning calorimeter and Vickers micro-hardness test. The results show that welding heat input has a significant effect on the hardness of the SZ. Under high welding heat input condition, a higher welding speed is beneficial for improving the hardness of the SZ. However, when the welding heat input is low, the hardness of the SZ elevates with increasing the rotation speed. The hardness of the SZ decreases after post-welded heat treatment due to overaging. The joints welded at 500 r/min and 100 mm/min show a high resistance to overaging. The reduction of hardness in the SZ is only 3.8%, while in other joints, the reduction is more than 10%. The morphology of strengthening precipitates plays important roles for the improvement of hardness.展开更多
The effect of inhaled nano-TiO2 on lung histology and serum biochemical indexes is evaluated in healthy and adult Kunming mice（eight in each group）after exposure to TiO2 aerosols（1 500 mg/m3）in a sealed chamber.An...The effect of inhaled nano-TiO2 on lung histology and serum biochemical indexes is evaluated in healthy and adult Kunming mice（eight in each group）after exposure to TiO2 aerosols（1 500 mg/m3）in a sealed chamber.Another eight mice are exposed to indoor air to be served as a control group.Lung tissue and blood are collected after euthanizing the animals.The results show that lactate dehydrogenase（LDH）activity increases in all experimental groups.Alanine aminotransferase（ALT）activity and blood urea nitrogen（BUN）levels are increased in the group exposed to TiO2 aerosols for 28 d,and creatinine（Cr）levels are increased in 14 d and 28 d samples（P0.05）.No obvious changes are observed in other serum indexes.Lungs of mice exposed to 28 d exposure show significant but moderate increase in pulmonary inflammation,and many TiO2 particles are found in the interstitium of pulmonary alveoli.展开更多
Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and tre...Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO2 ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.展开更多
基金Project(61901110301)supported by the Aircraft Science Foundation,China
文摘The microstructure and hardness of the stir zone （SZ） with different welding heat inputs were investigated for friction stir-welded 2024-T3 aluminum by transmission electron microscopy, differential scanning calorimeter and Vickers micro-hardness test. The results show that welding heat input has a significant effect on the hardness of the SZ. Under high welding heat input condition, a higher welding speed is beneficial for improving the hardness of the SZ. However, when the welding heat input is low, the hardness of the SZ elevates with increasing the rotation speed. The hardness of the SZ decreases after post-welded heat treatment due to overaging. The joints welded at 500 r/min and 100 mm/min show a high resistance to overaging. The reduction of hardness in the SZ is only 3.8%, while in other joints, the reduction is more than 10%. The morphology of strengthening precipitates plays important roles for the improvement of hardness.
文摘The effect of inhaled nano-TiO2 on lung histology and serum biochemical indexes is evaluated in healthy and adult Kunming mice（eight in each group）after exposure to TiO2 aerosols（1 500 mg/m3）in a sealed chamber.Another eight mice are exposed to indoor air to be served as a control group.Lung tissue and blood are collected after euthanizing the animals.The results show that lactate dehydrogenase（LDH）activity increases in all experimental groups.Alanine aminotransferase（ALT）activity and blood urea nitrogen（BUN）levels are increased in the group exposed to TiO2 aerosols for 28 d,and creatinine（Cr）levels are increased in 14 d and 28 d samples（P0.05）.No obvious changes are observed in other serum indexes.Lungs of mice exposed to 28 d exposure show significant but moderate increase in pulmonary inflammation,and many TiO2 particles are found in the interstitium of pulmonary alveoli.
基金Projects(U1530136,51375407)supported by the National Natural Science Foundation of China
文摘Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO2 ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.
