As for many of the aluminium alloys, Y alloy age hardens spontaneously at normal temperatures after solution heat treating. In contrast, R.R. alloys remain soft afterwards, until deliberately heat treated again by precipitation hardening for artificial ageing.[3] This simplifies their machining in the soft state, particularly where component blanks are made by a subcontractor and must be shipped to another site before machining. For R.R.56 the solution treatment is to quench from 530°C and ageing is carried out at 175°C.[3] For R.R.50, the solution treatment may be omitted and the metal taken directly to precipitation hardening (155°C-170°C).[14]
After solution treatment, the tensile strength of the alloy increases, but its Young's modulus decreases. The second stage of artificial aging increases the strength slightly, but also restores or improves the modulus.[15]
