AMS 2770
Heat Treatment of Wrought Aluminum Alloy Parts
Solution heat treatment, quenching, natural and artificial ageing, and annealing of wrought aluminum alloy parts (2000 series, 6000 and 7000 series alloys such as 2024, 6061, 7050 and 7075) by the part manufacturer.
What AMS 2770 specifies
AMS 2770 governs heat treatment of finished or semi-finished wrought aluminum parts, as distinct from raw stock (AMS 2772) and castings (AMS 2771). Its tables list, per alloy, the solution temperature — 2024 near 920 °F (495 °C), 6061 near 985–1000 °F (530–540 °C), 7075 at 870–900 °F (465–480 °C) — the quenchant (water at or below 100 °F, hot water or polymer) and the ageing cycle, for example 6061-T6 at 350 °F (175 °C) for 8 h and 7075-T6 at 250 °F (121 °C) for 24 h, plus the two-stage T73/T76 overageing and O-temper annealing. Quench delay is limited by thickness (5 s up to 0.016 in, 7 s to 0.031 in, 10 s to 0.090 in, 15 s above) and solution furnaces must hold ±10 °F (±6 °C). It limits reheat cycles, requires control of high-temperature oxidation and eutectic melting, and accepts lots by hardness and electrical conductivity (AMS 2658) with tensile tests where specified.
Tests and the drawing call-out
Tests the document imposes
- Hardness (Rockwell B / E / 15T per ASTM E18) and eddy-current electrical conductivity per AMS 2658 on each lot
- Tensile test per ASTM B557 on parts or coupons when specified
- Metallographic check for eutectic melting, high-temperature oxidation and Alclad diffusion when specified
- Quench delay timing and quenchant temperature record
- Furnace TUS / SAT per AMS 2750 (solution furnaces ±10 °F)
How to cite it
Drawing call-out
SOLUTION HEAT TREAT AND AGE PER AMS 2770 TO 6061-T6; HARDNESS AND CONDUCTIVITY PER AMS 2658Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Heat treatments specified to AMS 2770
| Treatment | Role | Cost |
|---|---|---|
Age T6 (Aluminum) is a precipitation-hardening condition for 6061 and 6063 and 2024 and 7075. | Governing | $$ |
Age T651 (Aluminum) is a precipitation-hardening condition for 6061 plate and 2024 plate and 7075 plate. | Governing | $$ |
Age T73 (Aluminum) is a precipitation-hardening condition for 7075 and 7050 (alloy-specific overage condition). | Governing | $$$ |
Aluminum O-temper annealing removes strain hardening and produces the softest standard wrought condition. | Governing | $$ |
AMS 2770 — frequently asked
Why is quench delay so short?
Between leaving the furnace and entering the water the part cools through the range where copper- and zinc-bearing phases precipitate on grain boundaries; on thin sheet that happens in seconds and costs strength and corrosion resistance, 7075 and 2024 especially. Hence 5 s for sheet up to 0.016 in and 15 s only for sections over 0.090 in, timed from door opening to full immersion.
Can a machined 6061 part be re-solution treated to T6?
Yes. Parts machined in O or T4 condition are solution treated at about 985–1000 °F, quenched and aged at 350 °F for 8 h. Expect quench distortion on thin or asymmetric sections, and note that the sheet limits the number of re-solution cycles because each one coarsens grain and thins any Alclad layer.
What is the difference between T6 and T73 for 7075?
T6 (250 °F for 24 h) gives peak strength but poor short-transverse stress-corrosion resistance; T73 is a two-stage overage that gives up roughly 10–15 % strength for full SCC resistance. The tempers are told apart by conductivity per AMS 2658: T73 must read 40 % IACS or more while T6 sits around 31–35 % IACS.
Which furnace class is needed?
Solution heat treating requires uniformity of ±10 °F (±6 °C) because 7075 melts incipiently a few degrees above 900 °F while under-temperature leaves phases undissolved; ageing tolerances are also ±10 °F for most alloys. AMS 2750 surveys and load thermocouples are part of the heat treater's certification.
AMS 2770 is copyrighted by SAE International. This page explains the document so a drawing can be read; it does not reproduce the standard. Purchase the current edition from the publisher. Official source ↗