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
Phase relation of the aluminium magnesium scandium system in the Al rich range at 430 ℃ was investigated by means of multiphase diffusion couples along with electron probe microanalysis, X ray diffraction and electro...Phase relation of the aluminium magnesium scandium system in the Al rich range at 430 ℃ was investigated by means of multiphase diffusion couples along with electron probe microanalysis, X ray diffraction and electron microscopy techniques. It consists of five single phase fields, four 2 phase fields and one 3 phase field. The maximum solid solubilities of Mg and Sc in α (Al) solid solution at 430 ℃ are about 15.27%Mg(mole fraction) and 0.33%Sc, respectively. The maximum solid solubilities of Sc in Mg 2Al 3 and Mg 17 Al 12 are about 1.08% and 0.03% at the same temperature. The diffusion path at 430 ℃ was constructed and interpreted by means of the Al Mg Sc equilibrium phase diagram assuming that local equilibrium is established at the phase boundaries.展开更多
The microstructural evolution characteristics of thermo-mechanically affected zone were investigated during friction stir processing (FSP) of the thixoformed AZ91D alloy. Simultaneously, an Al-rich surface layer was p...The microstructural evolution characteristics of thermo-mechanically affected zone were investigated during friction stir processing (FSP) of the thixoformed AZ91D alloy. Simultaneously, an Al-rich surface layer was prepared by combination of Al powder using FSP method. The results indicate that the dynamic recrystallization and mechanical separation (including splitting and fracture of the primary grains) are the main mechanisms of grain refinement. For the thixoformed alloy, the operation efficiency of these mechanisms is less than that of the permanent mould casting AZ91D alloy, thus its microstructural evolution is relatively slow and the resulting grain size is relatively large. These are attributed to the differences in their original microstructures. The Al-rich surface layer can obviously improve the corrosion resistance in NaCl aqueous solution. A proper solution heat treatment (at 415 ℃ for 1 h) can further increase the corrosion resistance. In order to improve corrosion resistance, increasing the amount and improving the distribution uniformity of the Al-rich phase are more effective than increasing the Al solubility in the matrix.展开更多
Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV...Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350°C exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.展开更多
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%.
文摘Phase relation of the aluminium magnesium scandium system in the Al rich range at 430 ℃ was investigated by means of multiphase diffusion couples along with electron probe microanalysis, X ray diffraction and electron microscopy techniques. It consists of five single phase fields, four 2 phase fields and one 3 phase field. The maximum solid solubilities of Mg and Sc in α (Al) solid solution at 430 ℃ are about 15.27%Mg(mole fraction) and 0.33%Sc, respectively. The maximum solid solubilities of Sc in Mg 2Al 3 and Mg 17 Al 12 are about 1.08% and 0.03% at the same temperature. The diffusion path at 430 ℃ was constructed and interpreted by means of the Al Mg Sc equilibrium phase diagram assuming that local equilibrium is established at the phase boundaries.
基金Project(2007CB613706) supported by the National Basic Research Program of ChinaProject(3ZS042-B25-003) supported by the Natural Science Foundation of Gansu Province, ChinaProject(SKL03004) supported by the Development Program for Outstanding Young Teachers in Lanzhou University of Technology, China
文摘The microstructural evolution characteristics of thermo-mechanically affected zone were investigated during friction stir processing (FSP) of the thixoformed AZ91D alloy. Simultaneously, an Al-rich surface layer was prepared by combination of Al powder using FSP method. The results indicate that the dynamic recrystallization and mechanical separation (including splitting and fracture of the primary grains) are the main mechanisms of grain refinement. For the thixoformed alloy, the operation efficiency of these mechanisms is less than that of the permanent mould casting AZ91D alloy, thus its microstructural evolution is relatively slow and the resulting grain size is relatively large. These are attributed to the differences in their original microstructures. The Al-rich surface layer can obviously improve the corrosion resistance in NaCl aqueous solution. A proper solution heat treatment (at 415 ℃ for 1 h) can further increase the corrosion resistance. In order to improve corrosion resistance, increasing the amount and improving the distribution uniformity of the Al-rich phase are more effective than increasing the Al solubility in the matrix.
基金the National Natural Science Foundation of China(No.52265043)Science and Technology Plan,Guizhou Province,China(No.ZK2021(267))+2 种基金Technology Achievements Application and Industrialization Project,Guizhou Province,China(No.2021(067))Cultivation Project of Guizhou University,China(No.2019(23))Lastly,we thank the Shanghai Synchrotron Radiation Facility(SSRF)for providing the synchrotron radiation beamtime.
文摘Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350°C exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.
