Effect of heat-treatment conditions on the properties of aluminum alloy semifinished products

Decomposition of the solid solution in commercial semiproducts from aluminum alloys

“…The shift of the thermokinetic diagram was confirmed later in [5] and [6] for alloy DI6 at about the same time. However, an analysis of these diagrams has shown a substantial difference in the shape of the C-curves.…”

“…It should also be taken into account that the segregation of a stable phase in cooling from the temperature of heating for quenching is always preceded by the segregation of a metastable phase. For example, when alloy D 16 is heated for quenching the S-and 0-phases segregate earlier than the S'-and 0'-phases [6] or in AI -Li alloys the 5-phase segregates earlier than the 6'-phase [13]. The segregation of a metastable phase is possible if the solid solution is supersaturated enough with this or that component in the region of low temperatures.…”

“…However, an analysis of these diagrams has shown a substantial difference in the shape of the C-curves. Work [5] has shown the existence of one minimum of stability of the solid solution, and work [6] has shown that there are three minima. On the basis of the vertical section of the phase diagram of the A1 -Cu -Mg (Cu/Mg = 3) system presented in [7] these minima have been placed in correspondence with the following phase regions: (I) %.~ol + S + 0 (for a temperature range of 460-380~ (H) Cts.~o I + S' + 0' (380-270~ and (III) Ors.so I + GPB (270 -120~ where Ors.so L is a solid solution based on AI, GPB are Guinier-Preston-Bagaryatskii zones, S and S' are used to denote the AI2CuMg phase, and 0 and 0' are used to denote the CuA12 phase.…”

“…In addition, we determined in [6] the critical hardening rate Vcr= 30 K/sec for alloy D16 from the variation of the crack and corrosion resistances.…”

Copper Redistribution during Corrosion of Aluminum Alloys

“…22 Pitting in NaCl solution.-Using a procedure similar to that described above for NaOH, we examined Cu redistribution on the surface of Al 2024-T3 exposed to 0.5 M NaCl solution at open-circuit potential for different times. It is well known that Al 2024-T3 samples undergo pitting and intergranular corrosion 25,26 in a neutral chloride solution, and it was recently shown that that corrosion of this alloy in acid chloride results in a fourfold increase of the copper content on the surface of this alloy. 27 We believe that this enrichment in copper probably results from the selective dissolution of S-phase intermetallics.…”