Binary Al-4Mg alloy have been deformed by hot torsion at 300-500 deg C andstrain rates of 0.006-1.587 s^(-1) to a true strain of 5.5. The specimens were annealed in vacuumfor 1.5 h at 500 deg C and then water quenched...Binary Al-4Mg alloy have been deformed by hot torsion at 300-500 deg C andstrain rates of 0.006-1.587 s^(-1) to a true strain of 5.5. The specimens were annealed in vacuumfor 1.5 h at 500 deg C and then water quenched. The study indicates that the dynamicrecrystallization occurs during hot torsion of Al-4Mg alloy in a certain range of Z parameter(Zener-Hollmon Parameter), i.e. 19.3 <= lnZ <=24.8. Increasing the strain rate at higher deformationtemperature or reducing the strain rate at lower deformation temperature accelerates the occurrenceof dynamic recrystallization in the alloy.展开更多
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
The 430 ℃ isothermal section of the Al 4Mg Sc Zr quaternary system in the Al rich range was determined by means of equilibrium alloys with the use of microstructure, X ray diffraction analysis and electron probe micr...The 430 ℃ isothermal section of the Al 4Mg Sc Zr quaternary system in the Al rich range was determined by means of equilibrium alloys with the use of microstructure, X ray diffraction analysis and electron probe microanalysis. There coexist three single phase fields, two two phase fields and one three phase field. It is established that the phase Al 3Sc 10.5 Zr 00.5 with L1 2 structure and Al 3Zr 10.8 Sc 00.2 with DO 23 structure are in equilibrium with the α solid solution, Zr being dissolved in Al 3Sc, further substituting for about 50% Sc(mole fraction) whilst Sc is present in the phase Al 3Zr and the maximum substitution for Zr is about 20%.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
Hydration mechanism of tabular alumina carbon composites reinforced by Al4C3 in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 ℃ to 85 ℃. It is shown...Hydration mechanism of tabular alumina carbon composites reinforced by Al4C3 in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 ℃ to 85 ℃. It is shown that hydration mechanism of the composites is chemical reaction control at 44.3 ℃-84 ℃ in H2O（g）. The hydration was controlled by diffusion from 24.7 ℃ to 33 ℃. The ratio of added Mg/Al influences the HMOR of the composites.The mechanism of HMOR of the composites with different ratios of Mg/Al can be discovered by means of SEM analysis. The active Mg/Al powder and flake graphite inside give the composites outstanding hot strength resulting from the interlocking structure of Al4C3 crystals at high temperature. Besides, the matrix changes into the Al4C3 with high refractoriness. The method of preventing the hydration of tabular alumina carbon composites reinforced by Al4C3 in situ reaction was immersed in the wax at suitable temperature or storing them below 33 ℃ in a dry place or storing them with paraffin-coating.展开更多
基金The project was sponsored by the Education Administration Major Project for Science Research under the contract No. 99134.
文摘Binary Al-4Mg alloy have been deformed by hot torsion at 300-500 deg C andstrain rates of 0.006-1.587 s^(-1) to a true strain of 5.5. The specimens were annealed in vacuumfor 1.5 h at 500 deg C and then water quenched. The study indicates that the dynamicrecrystallization occurs during hot torsion of Al-4Mg alloy in a certain range of Z parameter(Zener-Hollmon Parameter), i.e. 19.3 <= lnZ <=24.8. Increasing the strain rate at higher deformationtemperature or reducing the strain rate at lower deformation temperature accelerates the occurrenceof dynamic recrystallization in the alloy.
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.
文摘The 430 ℃ isothermal section of the Al 4Mg Sc Zr quaternary system in the Al rich range was determined by means of equilibrium alloys with the use of microstructure, X ray diffraction analysis and electron probe microanalysis. There coexist three single phase fields, two two phase fields and one three phase field. It is established that the phase Al 3Sc 10.5 Zr 00.5 with L1 2 structure and Al 3Zr 10.8 Sc 00.2 with DO 23 structure are in equilibrium with the α solid solution, Zr being dissolved in Al 3Sc, further substituting for about 50% Sc(mole fraction) whilst Sc is present in the phase Al 3Zr and the maximum substitution for Zr is about 20%.
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Funded by the National Torch Plan of China(No.2005EB031110)the Key Scientific and Technical Innovation Project of Xi’an University of Architecture and Technology(No.zx 0402)
文摘Hydration mechanism of tabular alumina carbon composites reinforced by Al4C3 in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 ℃ to 85 ℃. It is shown that hydration mechanism of the composites is chemical reaction control at 44.3 ℃-84 ℃ in H2O（g）. The hydration was controlled by diffusion from 24.7 ℃ to 33 ℃. The ratio of added Mg/Al influences the HMOR of the composites.The mechanism of HMOR of the composites with different ratios of Mg/Al can be discovered by means of SEM analysis. The active Mg/Al powder and flake graphite inside give the composites outstanding hot strength resulting from the interlocking structure of Al4C3 crystals at high temperature. Besides, the matrix changes into the Al4C3 with high refractoriness. The method of preventing the hydration of tabular alumina carbon composites reinforced by Al4C3 in situ reaction was immersed in the wax at suitable temperature or storing them below 33 ℃ in a dry place or storing them with paraffin-coating.
