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Specification Guide · AMS · Aluminum
AMS 4050 —
What It Covers and When It's Required
AMS 4050 is the SAE Aerospace Material Specification governing the production, chemistry, mechanical properties, and inspection requirements for
7050-T7451 aluminum alloy plate. It is the specification you will see called out on aerospace structural drawings whenever thick-section 7050 plate is required — and it mandates
ultrasonic inspection as a condition of acceptance.
AMS 4050
Aluminum Alloy, Plate, 6.2Zn-2.3Cu-2.2Mg-0.12Zr (7050-T7451)
Issuing body
SAE International (Aerospace Material Specifications)
Temper covered
T7451 — solution treated, over-aged, stress relieved by stretching
Thickness range
0.500 in (12.7 mm) through 6.000 in (152.4 mm) and above, depending on revision
UTS (typical)
76 ksi (524 MPa), longitudinal; spec minimum 76 ksi in the thinnest range, decreasing with thickness
Yield strength (typical)
68 ksi (469 MPa), longitudinal; spec minimum about 66 ksi in the thinnest range, decreasing with thickness
Elongation minimum
7–9% (thickness dependent), longitudinal; short-transverse requirements also apply
UT inspection
Mandatory —
ultrasonic inspection per AMS-STD-2154; AMS 4050 calls out the acceptance class. Put the class on the drawing (Class A for primary structure) and confirm it on the mill cert
Chemistry control
Zn 5.7–6.7%, Cu 2.0–2.6%, Mg 1.9–2.6%, Zr 0.08–0.15%, Fe max 0.15%, Si max 0.12%
Certification required
Material Test Report (MTR) documenting chemistry, mechanical properties, heat/lot numbers, and UT results
Composition limits (wt%)
The chemistry line from the spec card as floating bars. Zn, Cu, Mg, and Zr are the four elements named in the spec title (6.2Zn-2.3Cu-2.2Mg-0.12Zr) and carry two-sided ranges; Fe and Si are maximums only, so their bars start at zero. Watch the axis: the second tab is about 40× finer.
Zn · Cu · Mg
Zr · Fe · Si
What AMS 4050 Controls
AMS 4050 is a comprehensive specification — it doesn't just set a minimum tensile strength. It controls chemistry tolerances, the heat treatment process (T7451 temper requirements), mechanical property minimums in the longitudinal and long-transverse directions (plus short-transverse above a thickness threshold), and — critically — mandates ultrasonic inspection before the plate can be shipped or accepted.[1]
The short-transverse direction properties matter particularly for thick plate: this is the through-thickness direction, and it's where 7050's design advantage over 7075 is most visible. AMS 4050 sets minimum tensile and yield requirements in the longitudinal and long-transverse directions, plus short-transverse above a thickness threshold, ensuring that the plate won't fail preferentially through its thickness — a critical requirement for bulkheads, spars, and other primary structure loaded in multiple directions.
The Ultrasonic Testing Requirement
AMS 4050 requires that all plate be ultrasonically inspected per AMS-STD-2154 prior to acceptance. This immersion or contact UT scan checks the full volume of the plate for internal discontinuities — voids, inclusions, laminations, and cracks — that are invisible to surface inspection and would only be discovered after significant machining has already been completed.[1][2]
The UT acceptance class specifies the maximum allowable discontinuity size; AMS-STD-2154 defines classes AAA, AA, A, B, and C, from most to least restrictive. AMS 4050 invokes AMS-STD-2154 and calls out the acceptance class, but the safest practice is to put the class on the drawing as well (Class A for primary structure) so there is no ambiguity, and then confirm the class on the mill cert when the material arrives. Accepting material to the wrong class can result in a nonconformance on a finished part.
In plain terms — why UT matters on thick plate
Imagine machining a 200-pound billet of aluminum down to a 15-pound structural part — only to find a crack or void revealed in the last operation, after 90% of the material and all of the machining labor has already been spent. That's the risk with thick aluminum plate that hasn't been
ultrasonically inspected. AMS 4050's UT requirement essentially guarantees that the billet is sound before it ever reaches the machine. The UT certification on the material test report is your documentation that this was done — and it's what your quality system needs to show during an aerospace audit.
How to Call It Out on a Drawing
The correct drawing callout for material to this specification is:
ALUMINUM ALLOY PLATE, 7050-T7451 PER AMS 4050
UT INSPECTION CLASS A PER AMS-STD-2154
AMS 4050 invokes AMS-STD-2154 and calls out the acceptance class, but listing the class on the drawing (Class A for primary structure) removes any ambiguity between the drawing, the purchase order, and the mill. Confirm the class on the mill cert on receipt. The material certification you receive from the supplier should reference AMS 4050 by number, list the lot and heat numbers, provide chemistry and mechanical test results, and confirm that ultrasonic inspection was performed and passed.
Procurement note
AMS 4050 material is not stocked by all distributors. It is a specialty aerospace specification and may require ordering from an aerospace-qualified service center or mill-direct. Lead times are typically 4–8 weeks depending on thickness and quantity. Factor this into your schedule — this is not off-the-shelf material. We can assist with sourcing and will verify all certifications on receipt.
Machining to AMS 4050?
We verify material certifications, UT records, and chemistry compliance before cutting. Our AS9100D quality system maintains full traceability from raw material cert to finished part.
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