The microstructure of an Al-4Cu-Mg alloy during isothermal heat treatment in the Strain Induced Melt Activation （SIMA） process was investigated and the kinetics of grain growth was analyzed, The grain growth during ...The microstructure of an Al-4Cu-Mg alloy during isothermal heat treatment in the Strain Induced Melt Activation （SIMA） process was investigated and the kinetics of grain growth was analyzed, The grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy coincided with the Ostwald ripening theory. During isothermal heat treatment, both grain shape and the high volume fraction of solid phase have significant effects on grain growth. Therefore, a new grain growth model based on the Ostwald ripening theory was proposed taking into consideration the grain shape and the volume fraction of solid phase. By comparing the calculated results with the experimental results, it was confirmed that the present model could be applied to grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy in the SIMA process.展开更多
The microstructure of a cold-deformed Al-4Cu-Mg alloy during semi-solid treatment was investigated, which shows that grain detachment and grain spheroidization processes during the semi-solid treatment are very import...The microstructure of a cold-deformed Al-4Cu-Mg alloy during semi-solid treatment was investigated, which shows that grain detachment and grain spheroidization processes during the semi-solid treatment are very important to control the fabricated semi-solid microstructures. For the two different processes, the driving force comes from the external heat source and the reduction in total interfacial area, respectively. The evolution models of microstructure morphology in the two processes were presented based on microstructure observations. It can be found that these models are useful to provide a reasonable estimated critical time of the evolution of microstructure during the semi-solid treatment.展开更多
Effects of the process parameters, including deformation temperature, punch velocity and extrusion ratio, on the deformation and microstructure characterization during the semi-solid extrusion of Al-4Cu-Mg alloy, were...Effects of the process parameters, including deformation temperature, punch velocity and extrusion ratio, on the deformation and microstructure characterization during the semi-solid extrusion of Al-4Cu-Mg alloy, were investigated. The experimental results show that the load decreases with an increase of deformation temperature and/or a decrease of punch velocity. When the displacement is more than 4 mm,the load decreases significantly with an increase of the deformation temperature, which is related to the high liquid fraction. The microstructure varies with the process parameters and deformation regions. It can be found that the dynamic recovery occurs during the semi-solid extrusion of Al-4Cu-Mg alloy at lower deformation temperature. Subsequently, the microstructure elongated gradually polygonizes with an increase of deformation temperature. So, the higher deformation temperature should be chosen during the semi-solid extrusion of Al-4Cu-Mg alloy because the grains polygonized and high liquid fractions are beneficial to deformation.展开更多
Al-7.5Si-4Cu cast alloy melt modified by Al-5Ti-B, RE and Al-10Sr master alloys were poured in the chromite sand moulds, to investigate comparatively the effects of individual or combined additions of grain refiners a...Al-7.5Si-4Cu cast alloy melt modified by Al-5Ti-B, RE and Al-10Sr master alloys were poured in the chromite sand moulds, to investigate comparatively the effects of individual or combined additions of grain refiners and modifiers on the mechanical properties, microstructures, grain refining and modification, and intermetallic compounds of the alloy. The results show that the mechanical properties and the microstructures of Al-7.5Si-4Cu cast alloys are improved immensely by combining addition of 0.8%Al-5Ti-B, 0.1%RE and 0.1%Al-10Sr grain refiners and modifiers compared with the individual addition and cast conditions. For individual addition condition, addition of 0.8%Al-5Ti-B master alloy can obtain superior tensile strength, Brinell hardness and finer equiaxedα（Al） dendrites. The alloy with 0.1%RE master alloy shows the highest improvement in ductility because the rare earth can purify the molten metal and change the shape of intermetallic compounds. While the alloy with 0.1%Al-10Sr modifier shows only good improvement in yield strength, and the improvement of other performance is unsatisfactory. The Al-10Sr modifier has a significant metamorphism for the eutectic silicon, but will make the gas content in the aluminum alloy melt increase to form serious columnar grain structures. The effects of grain refining and modification on mean area and aspect ratio have the same conclusions obtained in the mechanical properties and the microstructures analyses.展开更多
The effects of different contents of Sc addition on the microstructures and properties of the Al 4%Cu alloy were studied by tensile properties measurement, optical microscope, X ray diffraction analysis, scanning elec...The effects of different contents of Sc addition on the microstructures and properties of the Al 4%Cu alloy were studied by tensile properties measurement, optical microscope, X ray diffraction analysis, scanning electron microscope (SEM) and energy spectrum analysis. The experimental results show that rare earth element Sc is capable of refining the dendritic structure of the Al 4%Cu alloy, the tensile strength σ b and yield strength σ 0.2 just increase a little when the content of Sc is lower than 0.2%; when the content reaches 0.3%0.4%, σ b and σ 0.2 slightly decrease; but σ b and σ 0.2 rise again when the Sc content is 0.5%, though both of them are lower than those of the Al 4%Cu alloy without Sc addition. However, Sc addition has little influence on the elongation of the Al 4%Cu alloy. Adding Sc to the Al 4%Cu alloy, when the amount of Sc is lower than 0.2%, Sc mostly exists in the α (Al) solid solution; when the Sc content is in the range of 0.3%0.5%, only a part of Sc exists in the α Al solid solution, the rest appears in two ways: one is that Sc and Al form Al 3Sc which can strengthen the alloy, and the other, Sc interacts with Al and Cu to form AlCuSc phase.展开更多
基金financially supported by the Doctorate Creation Foundation of Northwestern Polytechnical University (No.200210)
文摘The microstructure of an Al-4Cu-Mg alloy during isothermal heat treatment in the Strain Induced Melt Activation （SIMA） process was investigated and the kinetics of grain growth was analyzed, The grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy coincided with the Ostwald ripening theory. During isothermal heat treatment, both grain shape and the high volume fraction of solid phase have significant effects on grain growth. Therefore, a new grain growth model based on the Ostwald ripening theory was proposed taking into consideration the grain shape and the volume fraction of solid phase. By comparing the calculated results with the experimental results, it was confirmed that the present model could be applied to grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy in the SIMA process.
基金This work was financially supported by the Doctorate Creation Foundation of Northwestern Polytechnical University (No.200210)
文摘The microstructure of a cold-deformed Al-4Cu-Mg alloy during semi-solid treatment was investigated, which shows that grain detachment and grain spheroidization processes during the semi-solid treatment are very important to control the fabricated semi-solid microstructures. For the two different processes, the driving force comes from the external heat source and the reduction in total interfacial area, respectively. The evolution models of microstructure morphology in the two processes were presented based on microstructure observations. It can be found that these models are useful to provide a reasonable estimated critical time of the evolution of microstructure during the semi-solid treatment.
基金Project(BK2005025) supported by the Fundamental Research Project of Jiangsu Province, China
文摘Effects of the process parameters, including deformation temperature, punch velocity and extrusion ratio, on the deformation and microstructure characterization during the semi-solid extrusion of Al-4Cu-Mg alloy, were investigated. The experimental results show that the load decreases with an increase of deformation temperature and/or a decrease of punch velocity. When the displacement is more than 4 mm,the load decreases significantly with an increase of the deformation temperature, which is related to the high liquid fraction. The microstructure varies with the process parameters and deformation regions. It can be found that the dynamic recovery occurs during the semi-solid extrusion of Al-4Cu-Mg alloy at lower deformation temperature. Subsequently, the microstructure elongated gradually polygonizes with an increase of deformation temperature. So, the higher deformation temperature should be chosen during the semi-solid extrusion of Al-4Cu-Mg alloy because the grains polygonized and high liquid fractions are beneficial to deformation.
基金Project (09C26279200863) supported by Technology Innovation Fund Project of High-tech Small and Medium Enterprises,Ministry of Science and Technology of ChinaProject (BA2011084) supported by Special Fund Project on Science and Technology Achievement Transformation of Jiangsu Province,China
文摘Al-7.5Si-4Cu cast alloy melt modified by Al-5Ti-B, RE and Al-10Sr master alloys were poured in the chromite sand moulds, to investigate comparatively the effects of individual or combined additions of grain refiners and modifiers on the mechanical properties, microstructures, grain refining and modification, and intermetallic compounds of the alloy. The results show that the mechanical properties and the microstructures of Al-7.5Si-4Cu cast alloys are improved immensely by combining addition of 0.8%Al-5Ti-B, 0.1%RE and 0.1%Al-10Sr grain refiners and modifiers compared with the individual addition and cast conditions. For individual addition condition, addition of 0.8%Al-5Ti-B master alloy can obtain superior tensile strength, Brinell hardness and finer equiaxedα（Al） dendrites. The alloy with 0.1%RE master alloy shows the highest improvement in ductility because the rare earth can purify the molten metal and change the shape of intermetallic compounds. While the alloy with 0.1%Al-10Sr modifier shows only good improvement in yield strength, and the improvement of other performance is unsatisfactory. The Al-10Sr modifier has a significant metamorphism for the eutectic silicon, but will make the gas content in the aluminum alloy melt increase to form serious columnar grain structures. The effects of grain refining and modification on mean area and aspect ratio have the same conclusions obtained in the mechanical properties and the microstructures analyses.
文摘The effects of different contents of Sc addition on the microstructures and properties of the Al 4%Cu alloy were studied by tensile properties measurement, optical microscope, X ray diffraction analysis, scanning electron microscope (SEM) and energy spectrum analysis. The experimental results show that rare earth element Sc is capable of refining the dendritic structure of the Al 4%Cu alloy, the tensile strength σ b and yield strength σ 0.2 just increase a little when the content of Sc is lower than 0.2%; when the content reaches 0.3%0.4%, σ b and σ 0.2 slightly decrease; but σ b and σ 0.2 rise again when the Sc content is 0.5%, though both of them are lower than those of the Al 4%Cu alloy without Sc addition. However, Sc addition has little influence on the elongation of the Al 4%Cu alloy. Adding Sc to the Al 4%Cu alloy, when the amount of Sc is lower than 0.2%, Sc mostly exists in the α (Al) solid solution; when the Sc content is in the range of 0.3%0.5%, only a part of Sc exists in the α Al solid solution, the rest appears in two ways: one is that Sc and Al form Al 3Sc which can strengthen the alloy, and the other, Sc interacts with Al and Cu to form AlCuSc phase.
