The formation of highly coherent double-shelled L1_(2) nano-precipitates in dilute Al–Er–Sc–Zr alloys was investigated with the combined use of Cs-corrected transmission electron microscopy characterization and fir...The formation of highly coherent double-shelled L1_(2) nano-precipitates in dilute Al–Er–Sc–Zr alloys was investigated with the combined use of Cs-corrected transmission electron microscopy characterization and first-principles energetics calculations. The double-shelled nano-precipitates are primarily featured with an Er-rich core surrounded by a Sc-rich inner shell and a Zr-rich outer shell. First-principles energetics analyses based on the classic homogenous nucleation theory suggested that once forms, this double-shell structure can be thermally stable. The predominant formation of this double-shell structure has thus both profound kinetic and thermodynamic origins. Its formation and stability preference to all other possible L1_(2) nano-structures would become more pronounced as its size increases, no matter what the solute ratio and aging temperature of interest.展开更多
Solute-induced grain boundary(GB) strengthening is eff ective in improving the toughness and tensile strength of polycrystalline alloys. In this work, GB segregation behaviors of solute elements in Al alloys and their...Solute-induced grain boundary(GB) strengthening is eff ective in improving the toughness and tensile strength of polycrystalline alloys. In this work, GB segregation behaviors of solute elements in Al alloys and their potential eff ects on GB binding have been systematically investigated from fi rst-principles energetics. The low-energy Σ3(111) and Σ11(113) are immune to vacancy segregation, while high-energy Al GBs, such as Σ13(320), Σ9(221), Σ5(210), and Σ5(310), can attract both vacancies and solutes. Under-sized elements(Ni, Fe, Co, Cu) and similar-sized elements(Si, Zn, Ag, and Ti) prefer interstitial or vacancy sites at the GB interface, while over-sized elements(Mg, Zr, Sc, Er) tend to substitute Al or vacancy-neighboring sites at the GB interface. Segregated vacancies weaken GBs. Under-sized Ni, Co, Cu, similar-sized Ti, and over-sized Zr, Er, can directly enhance Al GBs, while similar-sized Ag and over-sized Mg reduce the GB binding strength. Solute strengthening or weakening eff ects tend to be always mitigated, more or less, by GB-segregated vacancies.展开更多
基金financial support from the National Natural Science Foundation of China(No.51971249)the Natural Science Foundation of Shandong Province(No.ZR2020KE012)。
文摘The formation of highly coherent double-shelled L1_(2) nano-precipitates in dilute Al–Er–Sc–Zr alloys was investigated with the combined use of Cs-corrected transmission electron microscopy characterization and first-principles energetics calculations. The double-shelled nano-precipitates are primarily featured with an Er-rich core surrounded by a Sc-rich inner shell and a Zr-rich outer shell. First-principles energetics analyses based on the classic homogenous nucleation theory suggested that once forms, this double-shell structure can be thermally stable. The predominant formation of this double-shell structure has thus both profound kinetic and thermodynamic origins. Its formation and stability preference to all other possible L1_(2) nano-structures would become more pronounced as its size increases, no matter what the solute ratio and aging temperature of interest.
基金supported by the National Natural Science Foundation of China(No.51971249)the Natural Science Foundation of Shandong Province(No.ZR2020KE012)。
文摘Solute-induced grain boundary(GB) strengthening is eff ective in improving the toughness and tensile strength of polycrystalline alloys. In this work, GB segregation behaviors of solute elements in Al alloys and their potential eff ects on GB binding have been systematically investigated from fi rst-principles energetics. The low-energy Σ3(111) and Σ11(113) are immune to vacancy segregation, while high-energy Al GBs, such as Σ13(320), Σ9(221), Σ5(210), and Σ5(310), can attract both vacancies and solutes. Under-sized elements(Ni, Fe, Co, Cu) and similar-sized elements(Si, Zn, Ag, and Ti) prefer interstitial or vacancy sites at the GB interface, while over-sized elements(Mg, Zr, Sc, Er) tend to substitute Al or vacancy-neighboring sites at the GB interface. Segregated vacancies weaken GBs. Under-sized Ni, Co, Cu, similar-sized Ti, and over-sized Zr, Er, can directly enhance Al GBs, while similar-sized Ag and over-sized Mg reduce the GB binding strength. Solute strengthening or weakening eff ects tend to be always mitigated, more or less, by GB-segregated vacancies.
