Decomposition Processes in an Al-5% Zn-1% Mg Alloy

Transmission electron microscopy investigation of separated nucleation and in-situ nucleation in AA7050 aluminium alloy

“…The η' transformation into η is well established [5, 9-11, 32, 36], and 11 types of η have been reported [9,10,36]. However, the detailed mechanisms of the transition involving 4 variants of η' → 11 types of η are intriguing.…”

“…In the present study, these eleven types of η precipitates are proposed to be classified into four groups according to their habit planes, as illustrated in Table 2. Based on the nomenclature used by Degischer et al [9], the (0001) basal planes of η 1 , η 4 , η 9 , and η 11 (designated as Group 1) and those of η 2 , η 3 , and η 10 (designated as Group 2) are parallel to the (110) Al and (11 ത 1 ത ) Al habit planes, respectively. The η 5 , η 6 , and η 7 (designated as Group 3) and the η 8 (designated as Group 4) grow on the (1 ത 21 ത 0) planes parallel to the (11 ത 1 ത ) Al and (11 ത 2) Al habit planes, respectively.…”

“…approximately stoichiometric MgZn 2 [9][10][11]37]. According to the VASP calculation [35], η precipitates possess lattice parameters of a = 0.504 nm, c = 0.828 nm ≈ 4 dሺ111ሻ Al .…”

“…The corresponding model of precipitate hardening has been explored in previous works [4,8]. The precipitation sequence [2,4,[9][10][11][12][13][14] of super-saturated solid solution → GP zones → η' precipitates → η precipitates is well known. However, the precise transformation mechanisms of GP zones → η' and η' → η precipitates have not been elucidated.…”

Effect of Interdendritic Precipitations on the Mechanical Properties of GBF or EMS Processed Al-Zn-Mg-Cu Alloys

“…Fine-strengthening precipitate MgZn 2 (η phase) forms inside grains during age-hardening treatment. Precipitation evolution during the age-hardening of Al-Zn-Mg-Cu alloys is in the sequence of SSSS (supersaturated solid solution) → GP zone → η phase → η phase [15][16][17]. High strength can be attained by creating a microstructure containing high spatial uniformity of fine precipitates inside grains and a small fraction of coarse precipitates on the grain boundaries [18][19][20][21][22][23][24][25][26][27].…”