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
The effect of 0.5wt.%Zn addition on the microstructure and mechanical properties of Mg-3Y-2Nd-0.5Zr(WE32)alloy was investigated.The results indicate that WE32-0.5Zn alloy takes 48 h to reach peak hardness after solid ...The effect of 0.5wt.%Zn addition on the microstructure and mechanical properties of Mg-3Y-2Nd-0.5Zr(WE32)alloy was investigated.The results indicate that WE32-0.5Zn alloy takes 48 h to reach peak hardness after solid solution treatment at 525℃and aging at 200℃,10 h earlier than WE32 alloy,which implies an accelerated aging precipitation kinetics owing to the addition of 0.5wt.%Zn.A large quantity of finerod and rectangular block-like Zn-Zr precipitates in theα-Mg matrix are formed in the WE32-0.5Zn alloy,and numerous needle-likeβ1phases are distributed at both ends of the Zn-Zr precipitates at peak-aged condition.In peak-aged condition,the ultimate tensile strength considerably increases from 263.2 MPa(WE32)to 309.6 MPa(WE32-0.5Zn),and the elongation dramatically increases from 4.3%(WE32)to 8.9%(WE32-0.5Zn).Theβ’andβ1phases are the main precipitates of the WE32-0.5Zn alloy peak-aged at 200℃.Theβ’andβ1phases easily nucleate at the Zn-Zr precipitates,and theβ1phases are particularly likely to nucleate and grow at the interface between the two ends of the Zn-Zr precipitates,which accelerates aging precipitation kinetics and leads to a shorter time to achieve peak aging.展开更多
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
基金Projects(2019YFA0708802, 2020YFA0711104) supported by the National Key R&D Program of ChinaProject(U21B6004) supported by the National Natural Science Foundation of ChinaProject(2021GK1040) supported by Major Project of Scientific Innovation of Hunan Province,China。
基金Project(11727802)supported by the National Natural Science Foundation of ChinaProjects(2018CDJSK04XK09,106112017CDJQJ328840)supported by the Fundamental Research Funds for the Central Universities,China。
基金financial supports from the China Postdoctoral Science Foundation(Nos.2019TQ0193,2019M661497)the National Key Research and Development Program of China(No.2018YFB1106302)+1 种基金the National Natural Science Foundation of China(No.51821001)the Anhui Provincial Engineering Research Center of Aluminum Matrix Composites,China(No.2017WAMC002)。
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financially supported by the Natural Science Foundation of Inner Mongolia under Grant No.2022MS05045the Science and Technology Planning of Inner Mongolia under Grant No.2020GG0175the Project of State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization under Grant No.2021Z2351。
文摘The effect of 0.5wt.%Zn addition on the microstructure and mechanical properties of Mg-3Y-2Nd-0.5Zr(WE32)alloy was investigated.The results indicate that WE32-0.5Zn alloy takes 48 h to reach peak hardness after solid solution treatment at 525℃and aging at 200℃,10 h earlier than WE32 alloy,which implies an accelerated aging precipitation kinetics owing to the addition of 0.5wt.%Zn.A large quantity of finerod and rectangular block-like Zn-Zr precipitates in theα-Mg matrix are formed in the WE32-0.5Zn alloy,and numerous needle-likeβ1phases are distributed at both ends of the Zn-Zr precipitates at peak-aged condition.In peak-aged condition,the ultimate tensile strength considerably increases from 263.2 MPa(WE32)to 309.6 MPa(WE32-0.5Zn),and the elongation dramatically increases from 4.3%(WE32)to 8.9%(WE32-0.5Zn).Theβ’andβ1phases are the main precipitates of the WE32-0.5Zn alloy peak-aged at 200℃.Theβ’andβ1phases easily nucleate at the Zn-Zr precipitates,and theβ1phases are particularly likely to nucleate and grow at the interface between the two ends of the Zn-Zr precipitates,which accelerates aging precipitation kinetics and leads to a shorter time to achieve peak aging.
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Project(ZR2021QE136)supported by the Natural Science Foundation of Shandong Province,ChinaProject(2020B010186002)supported by the Key Research and Development Program of Guangdong Province,China。
