摘要
The frequent occurrence of hitherto unknown phase Pre-θ′-2 and unusual 1.5 cθ′thick θ′precipitate was observed by atomic-resolution scanning transmission electron microscopy in the well-studied Al-Cu alloys. This phenomenon is associated with heterogeneous precipitate nucleation and growth on preexisting dislocations introduced by slight deformation prior to aging. In this study, the precise structure details of Pre-θ′-2 was determined by atomic scale imaging, image simulation based on image forming theories and first principle calculations. Pre-θ′-2 has a well-defined ordered structure sandwiched between two 2 aAl(~1.5 cθ′) spaced Cu layers on {200}Alplanes. The strong structural similarities between Pre-θ′-2 and 1.5 cθ′ thick θ′ in terms of interfacial structure and thickness, coupled with energetic calculations and preliminary in-situ observations, lead us to propose a new precipitation path toward key strengthening phase θ′
The frequent occurrence of hitherto unknown phase Pre-θ’-2 and unusual 1.5 cθ’ thick θ’ precipitate was observed by atomic-resolution scanning transmission electron microscopy in the well-studied Al-Cu alloys. This phenomenon is associated with heterogeneous precipitate nucleation and growth on preexisting dislocations introduced by slight deformation prior to aging. In this study, the precise structure details of Pre-θ’-2 was determined by atomic scale imaging, image simulation based on image forming theories and first principle calculations. Pre-θ’-2 has a well-defined ordered structure sandwiched between two 2 aAl(～1.5 cθ’) spaced Cu layers on {200}Alplanes. The strong structural similarities between Pre-θ’-2 and 1.5 cθ’ thick θ’ in terms of interfacial structure and thickness, coupled with energetic calculations and preliminary in-situ observations, lead us to propose a new precipitation path toward key strengthening phase θ’.
基金
financial support from the National Natural Science Foundation of China (Nos. 51601060, 51235010, 51671086)
Natural Science Foundation of Hunan Province (No. 2018JJ3655)
the Major Project for Defense Basic Preresearch Program
the National Key R&D Program of China (No. 2017YFB0306300)
the National Key Basic Research Development Plan Funded Project of China (No. 2014CB046602)
the Innovationdriven Plan in Central South University (No. 2015CX002)
the Science and Technology Plan in Hunan Province (No. 2016RS2015)
the Fundamental Research Funds for the Central Universities of Central South University (No. 1053320180612)
