AMS 2801
Heat Treatment of Titanium Alloy Parts
Stress relief, annealing, solution treatment and ageing of titanium and titanium alloy parts (commercially pure grades, Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-6V-2Sn, Ti-10V-2Fe-3Al, Ti-15V-3Cr-3Al-3Sn and others) by the part manufacturer.
What AMS 2801 specifies
AMS 2801 controls how titanium parts are heat treated so that the two damage modes of processing — oxygen-enriched alpha case and hydrogen pickup — are prevented or removed. Per-alloy tables give, for Ti-6Al-4V, stress relief at about 900–1200 °F (480–650 °C) for 0.5–4 h, annealing at 1300–1450 °F (705–790 °C), and solution treatment at 1725–1775 °F (940–970 °C) with a water quench inside a short quench delay followed by ageing at 900–1100 °F (480–595 °C) for 4–8 h for the STA condition. Heating in air above about 1000 °F forms alpha case that must be removed by chemical milling or machining to a verified depth unless vacuum or inert atmosphere is used; hydrogen is controlled by atmosphere and checked by analysis against the material limit (typically 125–150 ppm). Parts must be free of chlorinated solvents, fingerprints and halide residues before heating. Acceptance is by tensile test for STA lots plus alpha-case and hydrogen checks.
Tests and the drawing call-out
Tests the document imposes
- Tensile test per ASTM E8/E8M on parts or coupons for solution-treated-and-aged lots
- Alpha case examination by metallographic cross-section (ASTM E3 / E407) or microhardness traverse; blue-etch anodize per AMS 2642 when specified
- Hydrogen content per ASTM E1447 (inert gas fusion) against the material specification limit
- Hardness per ASTM E18 for lot consistency
- Furnace TUS / SAT per AMS 2750; quench delay timing for solution treatment
How to cite it
Drawing call-out
HEAT TREAT PER AMS 2801, TI-6AL-4V, SOLUTION TREAT AND AGE TO AMS 4965 PROPERTIES; REMOVE ALL ALPHA CASEAngle brackets mark the choices the drawing must make; every finish page shows a completed example.
Heat treatments specified to AMS 2801
| Treatment | Role | Cost |
|---|---|---|
Solution Treat + Age (Ti) is a precipitation-hardening condition for Ti-6Al-4V and Ti-6Al-6V-2Sn and Ti-10V-2Fe-3Al. | Governing | $$$$ |
AMS 2801 — frequently asked
What is alpha case and why must it go?
A hard, brittle oxygen-enriched surface layer — roughly 0.002–0.005 in (50–125 µm) after an hour near 1750 °F in air — that cracks under fatigue and chips cutting tools. The sheet requires it to be prevented by vacuum or argon processing or removed afterwards by chemical milling or machining to a depth verified by metallography or microhardness.
Why the ban on chlorinated solvents?
Chloride residues cause hot-salt stress-corrosion cracking of titanium above about 500 °F, and fingerprints do the same. Parts are cleaned with approved alkaline or non-halogenated cleaners and handled with gloves before heat treatment; the heat treater will reject visibly contaminated parts.
Does hardness tell me Ti-6Al-4V is STA?
Not reliably: annealed Ti-6Al-4V reads about 30–36 HRC and STA about 36–41 HRC, overlapping enough that AMS 2801 requires tensile tests for STA acceptance; hardness is a lot-consistency check only. Order the tensile properties from AMS 4965 (bar) or the applicable material specification.
How much does STA improve Ti-6Al-4V?
From about 130 ksi (895 MPa) tensile and 120 ksi yield annealed to 150–160 ksi (1035–1100 MPa) tensile and about 140 ksi yield in sections up to roughly 1 in (25 mm). Thicker sections cannot be quenched fast enough and the benefit fades, which is why STA is specified for small, highly loaded parts.
AMS 2801 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 ↗