With the increasing use of Al-Si-Mg alloys in the automotive industry,the fatigue performance of Al-Si-Mg alloy has become a major concern with regard to their reliability.The fatigue characteristics and microcosmic m...With the increasing use of Al-Si-Mg alloys in the automotive industry,the fatigue performance of Al-Si-Mg alloy has become a major concern with regard to their reliability.The fatigue characteristics and microcosmic mechanism of an Al-Si-Mg alloy under multiaxial proportional loadings were investigated in this research.As low cycle fatigue life and material strengthening behavior are closely related,the effect of equivalent strain amplitude on the multiaxial fatigue properties was analyzed.Fatigue tests were conducted to determine the influence of equivalent strain amplitude on the multiaxial proportional fatigue properties.The fatigue life exhibits a stable behavior under multiaxial proportional loadings.The dislocation structures of the Al-Si-Mg alloy were observed by transmission electron microscopy（TEM）.The dislocation structure evolution of the Al-Si-Mg alloy under multiaxial proportional loadings during low cycle fatigue develops step by step by increasing fatigue cycles.Simultaneously,the dislocation structure changes with the change in equivalent strain amplitude under multiaxial proportional loadings.The experimental evidence indicates that the multiaxial fatigue behavior and life are strongly dependent on the microstructure of the material,which is caused by multiaxial proportional loadings.展开更多
In this study, the microstructure of B319 casting alloys and effects of five different casting conditions on microstructure were studied. Multi-scale microstructure was quantified in terms of secondary dendrite arm sp...In this study, the microstructure of B319 casting alloys and effects of five different casting conditions on microstructure were studied. Multi-scale microstructure was quantified in terms of secondary dendrite arm spacing （SDAS）, and Si particle size and aspect ratio. The effects of SDAS, Si aspect ratio and size on fatigue life were analyzed. The results indicate that the size and aspect ratio of Si particles are a function of SDAS which is dependent on cooling rate during solidification. The fatigue life decreases with SDAS increasing as SDAS is smaller than 30 pm while it increases with SDAS increasing as SDAS is larger than 60 ~tm. In addition, the fatigue life decreases with Si aspect ratio and size increasing at the same SDAS. Moreover, SDAS and Si particles have also influence on fatigue fracture, such as the area of cracks propagation region and the roughness of fatigue fracture. The cracks propagation area is smaller, and the fatigue fracture is similar to tensile fracture with larger SDAS. Besides, the longitudinal section of fatigue fracture is rougher with large SDAS and elongated Si particles.展开更多
基金supported by the Major State Basic Research and Development Program of China (No.2007CB714704)the Na-tional Natural Science Foundation of China (No.50771073)the Program for New Century Excellent Talents in Chinese Universities (No.NCET-05-0388)
文摘With the increasing use of Al-Si-Mg alloys in the automotive industry,the fatigue performance of Al-Si-Mg alloy has become a major concern with regard to their reliability.The fatigue characteristics and microcosmic mechanism of an Al-Si-Mg alloy under multiaxial proportional loadings were investigated in this research.As low cycle fatigue life and material strengthening behavior are closely related,the effect of equivalent strain amplitude on the multiaxial fatigue properties was analyzed.Fatigue tests were conducted to determine the influence of equivalent strain amplitude on the multiaxial proportional fatigue properties.The fatigue life exhibits a stable behavior under multiaxial proportional loadings.The dislocation structures of the Al-Si-Mg alloy were observed by transmission electron microscopy（TEM）.The dislocation structure evolution of the Al-Si-Mg alloy under multiaxial proportional loadings during low cycle fatigue develops step by step by increasing fatigue cycles.Simultaneously,the dislocation structure changes with the change in equivalent strain amplitude under multiaxial proportional loadings.The experimental evidence indicates that the multiaxial fatigue behavior and life are strongly dependent on the microstructure of the material,which is caused by multiaxial proportional loadings.
基金financially supported by the National Natural Science Foundation of China (No.50771073)General Motors Funded Project (No.1314)
文摘In this study, the microstructure of B319 casting alloys and effects of five different casting conditions on microstructure were studied. Multi-scale microstructure was quantified in terms of secondary dendrite arm spacing （SDAS）, and Si particle size and aspect ratio. The effects of SDAS, Si aspect ratio and size on fatigue life were analyzed. The results indicate that the size and aspect ratio of Si particles are a function of SDAS which is dependent on cooling rate during solidification. The fatigue life decreases with SDAS increasing as SDAS is smaller than 30 pm while it increases with SDAS increasing as SDAS is larger than 60 ~tm. In addition, the fatigue life decreases with Si aspect ratio and size increasing at the same SDAS. Moreover, SDAS and Si particles have also influence on fatigue fracture, such as the area of cracks propagation region and the roughness of fatigue fracture. The cracks propagation area is smaller, and the fatigue fracture is similar to tensile fracture with larger SDAS. Besides, the longitudinal section of fatigue fracture is rougher with large SDAS and elongated Si particles.
