Morphological evolution of GP zones and nanometer-sized precipitates in the AA2050 aluminium alloy
Journal
International Journal of Lightweight Materials and Manufacture
Journal Volume
1
Journal Issue
3
Pages
142-156
Date Issued
2018
Author(s)
Chung T.-F
Abstract
Cs-corrected high-angle-annular-dark-field scanning-transmission-electron microscopy (Cs-corrected HAADF-STEM) was employed to examine the phases in Al[sbnd]Cu[sbnd]Li alloy (AA2050), including GP(T1), GP(θ?) and GPB zones with their subsequent nanometer-sized products, T1 (Al2CuLi), θ′ (Al2Cu), and S (Al2CuMg) precipitates, respectively. Under the peak-aging condition, some solute-atom enriched clusters could still be found, and the newly-formed nucleus of GP(θ?) with a mono-layer {100} plane of Cu atoms occurred at the adjacent area of the joint between θ′ and S precipitates or the edge of an individual S precipitate. The transition of a single Cu-layer GP(θ?) → θ′ was presumed to be transformation via in-situ nucleation. The developing GP(θ?) zones and θ′ precipitates were easily subjected to soft impingement. However, hard impingement between two variants of θ′ presumably occurred, wherein one θ′ variant precipitate was blocked out by the other θ′ variant. As for the creep-ageing forming (CAF) treated sample, some precipitates of T1 and θ′ were found to have the cutting characteristic on specific ledges. ? 2018 The Authors
Type
journal article