To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are be...To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are being studied. The interface reactions between Al_(66)Fe_9Ti_(25)matrix and SiC reinforcement were investigated. It is determined that SiC is chemically incompatible with the Al_(66)Fe_9Ti_(25)matrix, Al_2O_3 barrier coating on SiC by sol-gel process was developed to minimize the interfacial reactions. On the other hand, a new type of Al_3Ti-based alloy having a L1_2 matrix with second phase precipitation has been developed. The quaternary alloys based on Al_(66)Fe_9Ti_(25)and modified with Nb additions, consist of a L1_2 matrix and D0_(22) second phase in the annealed state ,but the second phase can be dissolved by solution treatment and precipitated during high temperature aging.展开更多
A computer simulation study on dynamics for the precipitation of δ'(Al_3Li) ordered particles from a disor- dered matrix (α) in binary Al-Li alloys is performed using the microscopic Langevin equation. A unique ...A computer simulation study on dynamics for the precipitation of δ'(Al_3Li) ordered particles from a disor- dered matrix (α) in binary Al-Li alloys is performed using the microscopic Langevin equation. A unique precipitation mechanism is found near the ordering spinodal line. Different from the classical nucleation mechanism in the me- tastable region and the congruent ordering followed by spinodal decomposition in the instable region, a nonstoichi- ometric single ordered phase with composition fluctuations is formed by non-classical nucleation, and this ordered phase decomposes spinodally. It can be concluded that the precipitation dynamics of δ' phase from metastability to instability is gradual, and no sharp transition occurs near the mean-field spinodal line as the mean-field theory pre- dicts.展开更多
As a core functional refractory in the continuous casting process,the service reliability of the submerged entry nozzle(SEN)is directly related to the stability of continuous casting production,the quality of casting ...As a core functional refractory in the continuous casting process,the service reliability of the submerged entry nozzle(SEN)is directly related to the stability of continuous casting production,the quality of casting billets,and production efficiency.Al_(2)O_(3) inclusions clogging constitutes the predominant failure mode of SEN,particularly during continuous casting of high-grade steels.Although several studies in the literature have demonstrated that electric field application can mitigate SEN clogging to some extent,the underlying mechanism remains poorly understood,which hinders its widespread acceptance and practical implementation.The mechanism of preventing SEN clogging by applying a positive electric field was studied,and experimental verification was conducted on it in a certain steel plant.The results indicate that Al_(2)O_(3) inclusions exhibit a positive charge in molten steel under high-temperature(~1600℃)and low-oxygen-partial-pressure(≤20×10-6)conditions.In the continuous casting process at a Chinese steel plant,applying a positive electric field to the SEN effectively suppressed the migration of Al_(2)O_(3) inclusions toward the SEN wall,significantly enhancing its clogging resistance.展开更多
文摘To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are being studied. The interface reactions between Al_(66)Fe_9Ti_(25)matrix and SiC reinforcement were investigated. It is determined that SiC is chemically incompatible with the Al_(66)Fe_9Ti_(25)matrix, Al_2O_3 barrier coating on SiC by sol-gel process was developed to minimize the interfacial reactions. On the other hand, a new type of Al_3Ti-based alloy having a L1_2 matrix with second phase precipitation has been developed. The quaternary alloys based on Al_(66)Fe_9Ti_(25)and modified with Nb additions, consist of a L1_2 matrix and D0_(22) second phase in the annealed state ,but the second phase can be dissolved by solution treatment and precipitated during high temperature aging.
基金The project was financially supported by the National Science Foundation of China (59871039)
文摘A computer simulation study on dynamics for the precipitation of δ'(Al_3Li) ordered particles from a disor- dered matrix (α) in binary Al-Li alloys is performed using the microscopic Langevin equation. A unique precipitation mechanism is found near the ordering spinodal line. Different from the classical nucleation mechanism in the me- tastable region and the congruent ordering followed by spinodal decomposition in the instable region, a nonstoichi- ometric single ordered phase with composition fluctuations is formed by non-classical nucleation, and this ordered phase decomposes spinodally. It can be concluded that the precipitation dynamics of δ' phase from metastability to instability is gradual, and no sharp transition occurs near the mean-field spinodal line as the mean-field theory pre- dicts.
基金supported by the National Outstanding Youth Science Fund Project of National Natural Science Foundation of China(No.52302031)National Natural Science Foundation of China(No.51932008).
文摘As a core functional refractory in the continuous casting process,the service reliability of the submerged entry nozzle(SEN)is directly related to the stability of continuous casting production,the quality of casting billets,and production efficiency.Al_(2)O_(3) inclusions clogging constitutes the predominant failure mode of SEN,particularly during continuous casting of high-grade steels.Although several studies in the literature have demonstrated that electric field application can mitigate SEN clogging to some extent,the underlying mechanism remains poorly understood,which hinders its widespread acceptance and practical implementation.The mechanism of preventing SEN clogging by applying a positive electric field was studied,and experimental verification was conducted on it in a certain steel plant.The results indicate that Al_(2)O_(3) inclusions exhibit a positive charge in molten steel under high-temperature(~1600℃)and low-oxygen-partial-pressure(≤20×10-6)conditions.In the continuous casting process at a Chinese steel plant,applying a positive electric field to the SEN effectively suppressed the migration of Al_(2)O_(3) inclusions toward the SEN wall,significantly enhancing its clogging resistance.
