ASTM B918
Standard Practice for Heat Treatment of Wrought Aluminum Alloys
Standard practice for the solution heat treatment, quenching, precipitation (age) hardening and annealing of wrought aluminum alloys — sheet, plate, extrusions, forgings, bar and machined parts — in the 2000 series, 6000 series and 7000 series.
What ASTM B918 specifies
ASTM B918 is the industrial practice for heat treating wrought aluminum (the ASTM counterpart of AMS 2770). Its tables give, per alloy, the solution heat-treatment temperature — 2024 at about 920 °F (495 °C), 6061 at about 990 °F (530 °C), 7075 at 870–900 °F (465–480 °C) — the quenchant and maximum water temperature, the maximum quench delay by thickness (5 s to 0.016 in, 7 s to 0.031 in, 10 s to 0.090 in, 15 s above), the natural-ageing period for T3/T4 tempers and the artificial-ageing cycles for T6/T651 (6061: 350 °F / 175 °C for 8 h; 7075: 250 °F / 121 °C for 24 h) and for the two-stage T73/T76/T77 overaged tempers, plus annealing to O temper. It requires solution furnaces to hold ±10 °F (±6 °C), controls high-temperature oxidation (blistering) in air furnaces, limits re-solution treatments and Alclad diffusion, and refers to ASTM B557 tension tests, hardness and electrical conductivity (ASTM E1004) for acceptance.
Tests and the drawing call-out
Tests the document imposes
- Tension test per ASTM B557 by lot when specified
- Hardness per ASTM E18 (HRB / HRE / HR15T) and electrical conductivity per ASTM E1004 as lot screens
- Quench delay timing and quenchant temperature record
- Furnace temperature uniformity check (±10 °F) at the solution temperature
- Intergranular corrosion (ASTM G110) or exfoliation (ASTM G34) tests for 2000 series / 7000-series tempers when specified
How to cite it
Drawing call-out
SOLUTION HEAT TREAT AND AGE PER ASTM B918 TO 7075-T73; CONDUCTIVITY 40 % IACS MIN, HARDNESS PER ASTM E18Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Heat treatments specified to ASTM B918
| Treatment | Role | Cost |
|---|---|---|
Age T6 (Aluminum) is a precipitation-hardening condition for 6061 and 6063 and 2024 and 7075. | Alternative | $$ |
Age T651 (Aluminum) is a precipitation-hardening condition for 6061 plate and 2024 plate and 7075 plate. | Alternative | $$ |
Age T73 (Aluminum) is a precipitation-hardening condition for 7075 and 7050 (alloy-specific overage condition). | Alternative | $$$ |
Aluminum O-temper annealing removes strain hardening and produces the softest standard wrought condition. | Related | $$ |
ASTM B918 — frequently asked
Why is 7075 solution treated at only 870–900 °F while 6061 goes to 990 °F?
7075 has a low-melting eutectic just above 900 °F; exceeding it melts grain-boundary phases (incipient melting) and ruins the alloy, while 6061's magnesium silicide dissolves safely at 990 °F. That is why the practice has per-alloy tables and a ±10 °F furnace requirement.
What does natural ageing do after the quench?
2024 reaches most of its T4 strength in about 4 days at room temperature and 6061 in a few days; B918 sets the minimum natural-age time before properties are tested or artificial ageing starts, and freshly quenched 2024 or 7075 can be formed only in the first hours before it hardens.
Why is quench delay measured in seconds?
During transfer thin sections cool through the 750–500 °F range where copper and zinc phases precipitate on grain boundaries before the quench can freeze the solute in; a 20 s delay on 0.040 in 7075 sheet costs strength and intergranular-corrosion resistance. Delay limits therefore shrink with thickness — 5 s for the thinnest sheet, 15 s above 0.090 in.
Can conductivity replace tensile tests?
As a screen, yes: eddy-current conductivity per ASTM E1004 combined with hardness identifies the temper (7075-T6 about 31–35 % IACS, T73 at or above 40 % IACS, 6061-T6 about 40–45 % IACS). Tensile tests remain the acceptance test when the material or part specification requires them.
ASTM B918 is copyrighted by ASTM 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 ↗