Abstract
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-shaped
T
1
Al
2
CuLi
/
θ
′
Al
2
Cu
precipitates within the Al matrix. The electrochemically prepared samples were analyzed by scanning transmission electron microscopy and atom probe tomography for chemical mapping. The
θ
′
platelets, which are less than 2 nm thick, have the stoichiometric composition consistent with the expected Al
2
Cu equilibrium composition. Additionally, the Li distribution inside the
θ
′
platelets was found to equal the same value as in the matrix. The equally thin
T
1
platelet deviates from the formula (Al
2
CuLi) 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 (Al
2
CuLi) stoichiometry cannot be simply interpreted as a consequence of artifacts when measuring the Cu and Li concentrations inside the
T
1
platelet. 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 thin
T
1
platelet in the T8 tempering condition differs from the equilibrium composition of the thermodynamic stable bulk phase.
Original language | English (US) |
---|---|
Pages (from-to) | 1-11 |
Number of pages | 11 |
Journal | Advances in Condensed Matter Physics |
Volume | 2015 |
DOIs | |
State | Published - Jun 22 2015 |