Effects of Cu and Transition Metals on the Precipitation Behaviors of Metastable Phases at 523 K in Al-Mg-Si Alloys

Abstract

Morphology and crystal lattice of precipitates formed in the 6000 series Al-Mg-Si alloys containing Cu and transition metals of Cr and Fe (TM) after aging at 523 K were investigated by high-resolution transmission microscopy (HRTEM). The precipitates in the Cu-bearing alloys are more finely and densely distributed than those in the Cu-free alloys, whereas those in the TM-bearing alloys were coarser and formed inhomogeneously at the interfaces between the dispersoids and the matrix. Three kinds of metastable phases were detected by HRTEM as follows: β -phase in the balanced alloy, the TYPE-B precipitate in the excess-Si alloy, and Q -phase in the Cu-bearing alloys. No significant difference in between the precipitates in the TM-free alloys and in the TM-bearing alloys was observed. However, the Type-B precipitate in the excess-Si alloy was replaced with the β -phase by the addition of TM. This suggests that the chemical composition of the excess-Si alloy changes to the balanced composition, because the excess Si in the matrix has been consumed by the formation of the AlSi(Fe, Cr) and AlSiFe dispersoids.

Phase Identification of Nanometric Precipitates in Al-Si-Cu Aluminum Alloy by Hr-Stem Investigations

“…6b). Potential phase is β'-Mg 1.8 Si (Table 2) present (for example) in Al-Mg-Si alloys containing Cu and transition metals [16]. Crystal structure of proposed phase is presented in Figure 7 (view in [001]).…”

Correlative study of the thermoelectric power, electrical resistivity and different precipitates of Al–1.12Mg2Si–0.35Si (mass%) alloy

“…In order to optimize the microstructure of Al-Mg-Si ingots prior to their extrusion, it is necessary to understand the high-temperature precipitation of these alloys during cooling from the solutionizing temperature [4][5][6]. In the case of the ternary Al-Mg-Si alloys without excess of Si, previous works [7][8][9][10][11][12][13][14][15][16] showed that the precipitation sequence is rather well established and can be described as follows: supersaturated solid solution ? GP zones ?…”

Aging Behavior of Ultrafine-Grained Al–Mg–Si–X (X = Cu, Ag, Pt, Pd) Alloys Produced by High-Pressure Torsion

“…5 reveals that the age hardening is more prominent with Cu and Ag than Pt and Pd. Because Cu and Ag are important elements that facilitate the precipitation and keep the precipitates stable as known in normal coarse- grained samples, 18,20,25) it is suggested that they function in the same manner even in ultrafine-grained samples.…”