Study of microstructural evolution in friction-stir welded thin-sheet Al–Cu–Li alloy using transmission-electron microscopy

Where Does the Lithium Go? – A Study of the Precipitates in the Stir Zone of a Friction Stir Weld in a Li‐containing 2xxx Series Al Alloy

“…The notation a' has occasionally been used to the literature to identify the Al 3 (Li,Zr). [5,17] Here, the a' notation has been avoided because there is evidence that there is a continuum of solubility of Li and Zr in the L1 2 phase. [18] Though it is therefore possible to define all three -a', b', and d' -as one phase, the notations of b' and d' have been retained here as shorthand for Zr-rich and Li-rich L1 2 precipitates, respectively.…”

“…[3][4][5][6] As the b' phase (Al 3 Zr) and the d' phase (Al 3 Li) have the same crystal structure and similar lattice parameters, [7] it is not possible to determine which phase has precipitated within the stir zone by diffraction techniques. [5,6] Several studies of similar alloys report these particles to be of the d' phase based only on diffraction data, [3,4] but it has been observed by energy dispersive spectroscopy (EDS) that these particles contain significant amounts of Zr. [5,6] Early studies of the microstructural evolution in commercial Al alloys containing Li showed the d' phase to precipitate on top of the b' phase, creating a ''composite'' precipitate with a core-shell morphology.…”

“…[5,6] Several studies of similar alloys report these particles to be of the d' phase based only on diffraction data, [3,4] but it has been observed by energy dispersive spectroscopy (EDS) that these particles contain significant amounts of Zr. [5,6] Early studies of the microstructural evolution in commercial Al alloys containing Li showed the d' phase to precipitate on top of the b' phase, creating a ''composite'' precipitate with a core-shell morphology. [8][9][10][11][12] In their study of FSW stir zone precipitates in a 2xxx series, Li-containing Al alloy, Fonda & Bingert [6] posed the question of whether the precipitates were of uniform composition or if composite b'/d' precipitates formed upon cooling after FSW.…”

The effect of pin profiles on the microstructure and mechanical properties of underwater friction stir welded AA2519-T87 aluminium alloy

“…It is presently well demonstrated that friction stir welding (FSW) process can join aluminium plates with better joint properties over other welding processes (Barcellona et al 2006;Gachi et al 2011). The low heat input during FSW avoids the solidification defects and also avoids deteriorated metallurgical transformation that occur at the elevated temperatures (Shukla and Baeslack 2007). Despite, the heat generated during FSW can alter the precipitation behaviour of the aluminium material.…”

In-situ Investigation of the Fracture Behaviors of 2195-T8 Aluminum-Lithium alloy

“…The 2195-T8 alloy was selected in this paper. The primary strengthening phase T 1 precipitates uniformly distributed [8][9]. The T 1 precipitate phase acts as a non shearable barrier to hinder dislocation motion, and is considered to be responsible for the relatively good strength and fracture toughness properties of 2195-T8 when compared to other Al-Li alloys [10][11].…”