scholarly journals Characterization of Precipitation in Al-Li Alloy AA2195 by means of Atom Probe Tomography and Transmission Electron Microscopy

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Muna Khushaim ◽  
Torben Boll ◽  
Judith Seibert ◽  
Ferdinand Haider ◽  
Talaat Al-Kassab
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atom Probe Tomography ◽  
Stoichiometric Composition ◽  
Equilibrium Composition ◽  
Atom Probe ◽  
Chemical Mapping ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Matrix

The microstructure of the commercial alloy AA2195 was investigated on the nanoscale after conducting T8 tempering. This particular thermomechanical treatment of the specimen resulted in the formation of platelet-shapedT1Al2CuLi/θ′Al2Cuprecipitates within the Al matrix. The electrochemically prepared samples were analyzed by scanning transmission electron microscopy and atom probe tomography for chemical mapping. Theθ′platelets, which are less than 2 nm thick, have the stoichiometric composition consistent with the expected Al2Cu equilibrium composition. Additionally, the Li distribution inside theθ′platelets was found to equal the same value as in the matrix. The equally thinT1platelet deviates from the formula (Al2CuLi) in its stoichiometry and shows Mg enrichment inside the platelet without any indication of a higher segregation level at the precipitate/matrix interface. The deviation from the (Al2CuLi) stoichiometry cannot be simply interpreted as a consequence of artifacts when measuring the Cu and Li concentrations inside theT1platelet. The results show rather a strong hint for a true lower Li and Cu contents, hence supporting reasonably the hypothesis that the real chemical composition for the thinT1platelet in the T8 tempering condition differs from the equilibrium composition of the thermodynamic stable bulk phase.

scholarly journals Correlative atom probe tomography and scanning transmission electron microscopy reveal growth sequence of LPSO phase in Mg alloy containing Al and Gd

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Koji Inoue ◽  
Kenta Yoshida ◽  
Yasuyoshi Nagai ◽  
Kyosuke Kishida ◽  
Haruyuki Inui
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atom Probe Tomography ◽  
Scanning Transmission Electron Microscopy ◽  
Atom Probe ◽  
Lateral Growth ◽  
Lpso Phase ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

AbstractAtom probe tomography (APT) and transmission electron microscopy (TEM)/scanning transmission electron microscopy (STEM) have been used correlatively to explore atomic-scale local structure and chemistry of the exactly same area in the vicinity of growth front of a long-period stacking ordered (LPSO) phase in a ternary Mg–Al–Gd alloy. It is proved for the first time that enrichment of Gd atoms in four consecutive (0001) atomic layers precedes enrichment of Al atoms so that the formation of Al6Gd8 clusters occurs only after sufficient Al atoms to form Al6Gd8 clusters diffuse into the relevant portions. Lateral growth of the LPSO phase is found to occur by ‘ledge’ mechanism with the growth habit plane either {1$$\overline{1}$$ 1 ¯ 00} or {11$$\overline{2}$$ 2 ¯ 0} planes. The motion of ledges that give rise to lateral growth of the LPSO phase is considered to be controlled by diffusion of Al atoms.

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