The hardness, the tensile and the high-cycle fatigue（HCF） performances of 7075 aluminum alloy were investigated under temper T651, solution treated at 380 ℃ for 0.5 h and aged at different temperatures（150, 170, 1...The hardness, the tensile and the high-cycle fatigue（HCF） performances of 7075 aluminum alloy were investigated under temper T651, solution treated at 380 ℃ for 0.5 h and aged at different temperatures（150, 170, 190 ℃） for 10 hours. The optimal microstructures and the fatigue fracture surfaces were observed. The results show that the hardness and the tensile performances are at their optimum at T651, but the fatigue life is the shortest. The hardness and the elongation are the lowest after solution treatment. With the aging temperature increasing（150-190 ℃）, the HCF is improved. The crack is initiated from the impurity particles on the subsurface. Treated at 170 ℃,the area of the quasi-cleavage plane and the width of parallel serrated sections of the crack propagation are the largest. With increasing aging temperature, the dimple size of finally fracture surfaces becomes larger and the depth deeper.展开更多
Lithium-ion batteries are used in a wide range of applications.However,their cycle life suffers from the problem of capacity fade,which includes calendar and cycle aging.The effects of storage time,temperature and par...Lithium-ion batteries are used in a wide range of applications.However,their cycle life suffers from the problem of capacity fade,which includes calendar and cycle aging.The effects of storage time,temperature and partial charge-discharge cycling on the capacity fade of Li-ion batteries are investigated in this study.The calendar aging and cycle aging are presented based on the storage and cycling experiment on LiCoO_(2)/graphite cells under different storage temperature and different ranges of state of charge(SOC).Based on the measurement data,a one-component and a double-component aging model are presented to respectively describe the capacity fade caused by calendar and cycle aging.The calendar aging of LiCoO_(2)/graphite batteries is mainly affected by temperature and SOC during the storage.Mean SOC and change in SOC(ΔSOC)are the main factors affecting battery degradation during cycling operation.展开更多
Fatigue lives for the smooth and notched specimens of 8090 Al-Li alloy jn the different ageing conditions have been studied. For the smooth samples of 8090 alloy the artificial ageing results in an increase in fatigue...Fatigue lives for the smooth and notched specimens of 8090 Al-Li alloy jn the different ageing conditions have been studied. For the smooth samples of 8090 alloy the artificial ageing results in an increase in fatigue life in comparison with natural ageing. On the contrary, the notched specimens of 8090 alloy in the naturally aged condition show higher fatigue life than in the peak-aged. The exposure to either the peak-aged or naturally aged leads to superior fatigue properties of Al-Li alloy to the traditional high strength aluminum alloys of 7075 and 2024, especially in the latter aged condition. In all ageing conditions, i,e. naturally, under-, peak- and over-aged, the peak-aged 8090 alloy displays the highest fatigue life and the over-aged material has a minimum value at the same stress amplitude. The difference in fatigue life is mainly attributable to the size and distribution of strengthening precipitates as well as the wide of precipitate free zones (PFZ's) along grain boundaries.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.51375500,and 51375162)Scientific Research Project of Hunan Province Department of Education(No.17C0886)Open Funded Projects of Hunan Provincial Key Laboratory of Health Maintenance for Mechanical Equipment(No.201605)
文摘The hardness, the tensile and the high-cycle fatigue（HCF） performances of 7075 aluminum alloy were investigated under temper T651, solution treated at 380 ℃ for 0.5 h and aged at different temperatures（150, 170, 190 ℃） for 10 hours. The optimal microstructures and the fatigue fracture surfaces were observed. The results show that the hardness and the tensile performances are at their optimum at T651, but the fatigue life is the shortest. The hardness and the elongation are the lowest after solution treatment. With the aging temperature increasing（150-190 ℃）, the HCF is improved. The crack is initiated from the impurity particles on the subsurface. Treated at 170 ℃,the area of the quasi-cleavage plane and the width of parallel serrated sections of the crack propagation are the largest. With increasing aging temperature, the dimple size of finally fracture surfaces becomes larger and the depth deeper.
基金supported by Shandong University Seed Fund Program for International Research Cooperation。
文摘Lithium-ion batteries are used in a wide range of applications.However,their cycle life suffers from the problem of capacity fade,which includes calendar and cycle aging.The effects of storage time,temperature and partial charge-discharge cycling on the capacity fade of Li-ion batteries are investigated in this study.The calendar aging and cycle aging are presented based on the storage and cycling experiment on LiCoO_(2)/graphite cells under different storage temperature and different ranges of state of charge(SOC).Based on the measurement data,a one-component and a double-component aging model are presented to respectively describe the capacity fade caused by calendar and cycle aging.The calendar aging of LiCoO_(2)/graphite batteries is mainly affected by temperature and SOC during the storage.Mean SOC and change in SOC(ΔSOC)are the main factors affecting battery degradation during cycling operation.
文摘Fatigue lives for the smooth and notched specimens of 8090 Al-Li alloy jn the different ageing conditions have been studied. For the smooth samples of 8090 alloy the artificial ageing results in an increase in fatigue life in comparison with natural ageing. On the contrary, the notched specimens of 8090 alloy in the naturally aged condition show higher fatigue life than in the peak-aged. The exposure to either the peak-aged or naturally aged leads to superior fatigue properties of Al-Li alloy to the traditional high strength aluminum alloys of 7075 and 2024, especially in the latter aged condition. In all ageing conditions, i,e. naturally, under-, peak- and over-aged, the peak-aged 8090 alloy displays the highest fatigue life and the over-aged material has a minimum value at the same stress amplitude. The difference in fatigue life is mainly attributable to the size and distribution of strengthening precipitates as well as the wide of precipitate free zones (PFZ's) along grain boundaries.
