Microstructural evolution in directionally solidified Al-Cu-Mg ternary eutectic

Microstructure evolution during directional solidification of off-eutectic Al-Cu-Mg alloys

“…Closer examination of the eutectic in alloy #1 shows it to be composed of two different morphologies: somewhat coarser regions of intermixed Al and Al 2 CuMg and very fine regions of three-phase eutectic. The ternary regions exhibit the strong lamellar tendency between Al and Al 2 CuMg observed by [8,19] and others. The three distinct types of microstructure in alloy #1 can be used to determine its apparent solidification pathway.…”

“…The reader is directed to ref. [8] for more details about the working principle of this furnace. The processed length of each sample was approximately 75 mm which ensured that the sample had sufficient time to establish a stable microstructure.…”

“…The growth mechanisms of higher-order eutectic systems have become a subject of interest in recent years, with researchers examining both invariant and univariant coupled growth. Al-Cu-Ag has emerged as a model system of particular interest [3][4][5][6][7], with recent efforts extending to related Al-Cu-Mg alloys [8][9][10]. Newly published work by the authors showed that in directional solidification of Al-Cu-Mg with nominally the invariant ternary eutectic composition [L ⇆ α(Al) + θ(Al 2 Cu) + S(Al 2 CuMg)], the system was able to maintain stable, three-phase coupled growth over a range of liquid compositions, solidification velocities and thermal gradients, and to be able to accommodate a range of compositions within the ternary eutectic itself [8].…”

“…Al-Cu-Ag has emerged as a model system of particular interest [3][4][5][6][7], with recent efforts extending to related Al-Cu-Mg alloys [8][9][10]. Newly published work by the authors showed that in directional solidification of Al-Cu-Mg with nominally the invariant ternary eutectic composition [L ⇆ α(Al) + θ(Al 2 Cu) + S(Al 2 CuMg)], the system was able to maintain stable, three-phase coupled growth over a range of liquid compositions, solidification velocities and thermal gradients, and to be able to accommodate a range of compositions within the ternary eutectic itself [8]. By adjusting processing conditions, pure ternary eutectic or a bimodal structure consisting of two-phase cells and highly regular ternary eutectic could be produced.…”

“…Additional investigations of the microstructure evolution and solidification paths in Al-Cu-Mg alloys can be found in [13][14][15][16]. The goal of the current work is to use similar solidification conditions as [8,9] to compare the microstructure growth behaviour of the eutectic composition alloy with those of offeutectic alloys having compositions: (a) on the Al-Al 2 Cu monovariant line, (b) within Al 2 Cu and Al 2 CuMg primary crystallization fields, and (c) at the end of Al 2 Cu-Al 2 CuMg tie line.…”