First-principle investigation on the interfacial structure evolution of the δ’/θ’/δ’ composite precipitates in Al-Cu-Li alloys
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2020年第23期
论文作者：Shuo Wang Chi Zhang Xin Li Houbing Huang Junsheng Wang
摘 要：The precipitation sequence in Al-Cu-Li alloys is sensitively dependent on the Cu/Li ratio.In the low ratio Cu/Li alloys of 1-2.5,the δ’ phases usually nucleate and grow from the 0’ precipitates,forming δ’/θ’/δ’composite precipitates.In this work,we present a first-principle study on atomic structures and their relative stabilities of the growing δ’/θ’/δ’ composite precipitates in Al-Cu-Li alloys.Based on the analysis of the interface formation energy,constituted interface and coherent strains energies,an "anti-phase1/2 [110]" relationship for the opposite δ’ has been proposed when the inward θ’ has an odd number of Cu-layers.It may be achieved by translating one side of the δ’ by 2（1/2）/2 a along the [110] slip direction,which is an energetically most favorable path.By analyzing the bonding characteristics,both the "zigzag Al-Li combined with Cu" and the "zigzag Al-Al" interracial terminals are found to control the interface structure of the growing δ’/θ’/δ’.According to the calculated ideal tensile strength,the "anti-phase 1/2[110]" structure is most stable to some extent.When Li atoms at the interface enter decohesion mode along the applied strain,the stable δ’/θ’/δ’ is prone to failure because of relatively weak Li-Al covalent bonds.Therefore,the really thin 8’ in 8’/0 ’/8’ composite precipitates may be explained by the continuous disassociation of Li atoms from the interface.In addition,a very weak Cu-Li covalent bond was suggested in the δ’/θ’/δ’ composite precipitates.This is in sharp contrast to previous reports.
Shuo Wang1，Chi Zhang1，Xin Li1，Houbing Huang1,2，Junsheng Wang1,2
1. School of Materials Science and Engineering,Beijing Institute of Technology2. Advanced Research Institute of Multidisciplinary Science,Beijing Institute of Technology
摘 要：The precipitation sequence in Al-Cu-Li alloys is sensitively dependent on the Cu/Li ratio.In the low ratio Cu/Li alloys of 1-2.5,the δ’ phases usually nucleate and grow from the 0’ precipitates,forming δ’/θ’/δ’composite precipitates.In this work,we present a first-principle study on atomic structures and their relative stabilities of the growing δ’/θ’/δ’ composite precipitates in Al-Cu-Li alloys.Based on the analysis of the interface formation energy,constituted interface and coherent strains energies,an "anti-phase1/2 [110]" relationship for the opposite δ’ has been proposed when the inward θ’ has an odd number of Cu-layers.It may be achieved by translating one side of the δ’ by 2（1/2）/2 a along the [110] slip direction,which is an energetically most favorable path.By analyzing the bonding characteristics,both the "zigzag Al-Li combined with Cu" and the "zigzag Al-Al" interracial terminals are found to control the interface structure of the growing δ’/θ’/δ’.According to the calculated ideal tensile strength,the "anti-phase 1/2[110]" structure is most stable to some extent.When Li atoms at the interface enter decohesion mode along the applied strain,the stable δ’/θ’/δ’ is prone to failure because of relatively weak Li-Al covalent bonds.Therefore,the really thin 8’ in 8’/0 ’/8’ composite precipitates may be explained by the continuous disassociation of Li atoms from the interface.In addition,a very weak Cu-Li covalent bond was suggested in the δ’/θ’/δ’ composite precipitates.This is in sharp contrast to previous reports.
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