6151-T6
Solution heat-treated, quenched and artificially aged. The standard temper under AMS 4125 for die forgings and rings.
Aerospace forgings
6151-T6 Aerospace Aluminium Forgings
6151 is a forging alloy from the 6xxx family, designed to fill intricate closed dies and to give a sound, fine-grained part with medium-high strength and very good corrosion resistance. Its aerospace specification is AMS 4125 (6151-T6 die forgings, rolled rings and forging stock). Metline supplies 6151 die forgings, hand forgings, rings and forging stock in T6 and T652 with full certification, worldwide.
- Alloy
- 6151 (Al-Mg-Si-Cr)
- Tempers
- O, T6, T652
- Specifications
- AMS 4125 · ASTM B247
- Forms
- Die & hand forgings, rings, stock
What is 6151 aluminium?
6151 is an aluminium-magnesium-silicon alloy with extra silicon (0.6–1.2 %) and a deliberate chromium addition (0.15–0.35 %). The higher silicon improves die fill and response to heat treatment, while chromium keeps the grain fine and resists recrystallisation during the repeated heating of a forging sequence.
The alloy was developed specifically for intricate die forgings, and its forging behaviour is its main advantage over 6061. It flows readily into deep ribs and thin webs, tolerates a wide hot-working window and gives forgings with consistent properties across thick and thin sections. In T6 temper its strength is comparable to 6061-T6, with excellent resistance to general corrosion and stress-corrosion cracking.
In aerospace, 6151 is chosen for moderately loaded fittings and housings where corrosion resistance and dimensional stability matter more than the peak strength of 2014 or 7075. Typical examples are equipment housings, valve and pump bodies, brackets, rings and wheel-type parts. In engineering outside aviation it appears in machine parts, pressure fittings and crankcase-style components.
6151 chemical composition (wt %)
Registered Aluminum Association limits, used by AMS 4125 and ASTM B247. The nominal analysis named in AMS 4125 is 0.90 Si – 0.62 Mg – 0.25 Cr.
| Element | Minimum | Maximum | Role |
|---|---|---|---|
| Silicon (Si) | 0.60 | 1.20 | Forms Mg2Si; excess silicon aids die fill and strength |
| Iron (Fe) | — | 1.00 | Impurity |
| Copper (Cu) | — | 0.35 | Small strength contribution |
| Manganese (Mn) | — | 0.20 | Grain control |
| Magnesium (Mg) | 0.45 | 0.80 | Main strengthening element with Si |
| Chromium (Cr) | 0.15 | 0.35 | Fine grain, resists recrystallisation |
| Zinc (Zn) | — | 0.25 | Impurity |
| Titanium (Ti) | — | 0.15 | Grain refiner |
| Others, each / total | — | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder |
Earlier versions of this page listed magnesium twice with conflicting limits. The table above gives the correct registered values.
Mechanical properties of 6151-T6 forgings
Typical values come from handbook data for 6151-T6. Forging specifications set minimum tensile, yield and elongation by direction (with or across the grain flow) and by section thickness, and those minimums, not the typical values, are what you should design to. The certificate for each lot reports the test results from the forging or a prolongation.
| Property (T6, typical) | Metric | Imperial |
|---|---|---|
| Tensile strength | ≈ 330 MPa | ≈ 48 ksi |
| Yield strength (0.2 %) | ≈ 295 MPa | ≈ 43 ksi |
| Elongation | ≈ 17 % | |
| Brinell hardness | ≈ 100 HB | |
| Shear strength | ≈ 220 MPa | ≈ 32 ksi |
| Fatigue strength (5 × 10⁸ cycles) | ≈ 80 MPa | ≈ 12 ksi |
Physical properties
- Density
- 2.71 g/cm³
- Modulus of elasticity
- ≈ 69 GPa
- Melting range
- ≈ 590 – 650 °C
- Thermal conductivity (T6)
- ≈ 170 W/m·K
- Electrical conductivity (T6)
- ≈ 45 % IACS
- Thermal expansion
- ≈ 23 µm/m·°C (20 – 100 °C)
Tempers for 6151 forgings
6151-T652
As T6, with a controlled 1–5 % cold compression after quenching to relieve residual stress. Specify it for hand forgings and blocks that will be heavily machined.
6151-O / F
Annealed or as-forged stock for further forging or heat treatment by the customer.
Buyers sometimes see 6151 offered in T651 or T74. T651 is a stretched temper used for plate and rolled bar, and T74 is an over-aged temper for 7xxx alloys; neither is a normal temper for 6151 forgings. If a drawing calls for one of them, we confirm with the customer before quoting.
6151 specifications
| Specification | Scope |
|---|---|
| SAE AMS 4125 | 6151-T6 die forgings, rolled or forged rings, and stock for forgings and rings |
| ASTM B247 (ASME SB-247) | Aluminium alloy die forgings, hand forgings and rolled ring forgings, including 6151 |
| QQ-A-367 (superseded federal specification) | Legacy aluminium alloy forgings; still found on older drawings |
| UNS | A96151 |
| AMS 2770 / AMS 2772 | Heat treatment of aluminium alloy parts and raw material |
| AMS-STD-2154 / ASTM B594 | Ultrasonic inspection of wrought products and forgings |
6151 has no common EN AW designation. European projects needing a similar forging usually specify EN AW-6082 or EN AW-6061 to EN 586, and we can offer either as an alternative.
Forging types and size envelope
| Forging type | Typical use | Notes |
|---|---|---|
| Closed-die forgings | Housings, brackets, fittings, valve bodies | Near-net shape to customer die or drawing |
| Open-die (hand) forgings | Blocks, bars and simple shapes for machining | Ordered with machining allowance; T652 recommended |
| Rolled and forged rings | Flanges, bearing housings, adaptor rings | Seamless rings with circumferential grain flow |
| Discs and pancakes | Wheel-type parts, covers | Upset forged for radial grain flow |
| Forging stock | Extruded or cast bar for customer forging | Supplied F or O temper |
Size limits depend on part geometry and the forging route chosen for each order, so we confirm the envelope for every enquiry against the drawing rather than quoting a single maximum.
Inspection and certification
- Chemistry: cast analysis reported on the certificate
- Mechanical tests: tensile tests from the forging, a prolongation or a separately forged coupon as the specification requires
- Hardness and conductivity: checks on each heat-treat lot to confirm correct temper
- Ultrasonic testing: to AMS-STD-2154 or ASTM B594 class on request
- Grain flow: macro-etch of a sacrificial part for first-article approval when specified
- Documents: EN 10204 3.1 certificate, heat-treat records and first-article report on request
Machining, welding and finishing
Machining
Good in T6, similar to 6061. Use sharp positive-rake tools and coolant. T652 forgings stay stable when large volumes are removed.
Welding
Weldable by TIG and MIG with 4043 filler, but welded joints lose T6 strength. Most aerospace 6151 parts are mechanically fastened.
Anodising
Takes sulphuric and hard anodic coatings; the higher silicon gives a slightly greyer film than 6061.
Corrosion
Very good in atmospheric and industrial conditions; no special stress-corrosion precautions are normally needed in T6.
Where 6151 forgings are used
- Aircraft equipment: pump and valve housings, actuator bodies, hydraulic manifolds
- Airframe fittings: moderately loaded brackets, hinges and secondary-structure fittings
- Rings and flanges: ducting flanges, adaptor rings and bearing housings
- Ground equipment: towbar fittings, jacks and handling-equipment parts
- Industrial: machine parts, pressure fittings and marine hardware
6151 compared with other forging alloys
| Property | 6151-T6 | 6061-T6 | 2014-T6 | 7075-T73 |
|---|---|---|---|---|
| Typical tensile strength | ≈ 330 MPa | ≈ 310 MPa | ≈ 485 MPa | ≈ 505 MPa |
| Die fill / forgeability | Excellent | Good | Good | Fair |
| Corrosion resistance | Very good | Very good | Fair | Good |
| Stress-corrosion resistance | Very good | Very good | Low in thick sections | Very good |
| Relative cost | Low | Low | Medium | High |
Choose 6151 or 6061 for corrosion-resistant fittings of moderate strength, 2014 for high-strength forgings where coatings will protect the part, and 7075-T73 or 7050 when both high strength and stress-corrosion resistance are needed.
How to order 6151 forgings
- SpecifyDrawing or forging envelope, alloy and temper (6151-T6 or T652), specification (AMS 4125 or ASTM B247), test and NDT requirements and quantity.
- ReviewWe confirm the forging route, test locations, certification and delivery terms (EXW, FOB, CIF or DAP).
- ApproveFirst-article inspection and grain-flow checks where the customer requires them.
- DocumentEN 10204 3.1 certificate with chemistry, mechanical and NDT results.
- ShipParts protected against corrosion and impact in export cases, by sea or air.
References and standards
- SAE AMS 4125 – Aluminum Alloy Forgings 0.90Si-0.62Mg-0.25Cr (6151-T6)
- ASTM B247 – Aluminum and Aluminum-Alloy Die Forgings, Hand Forgings and Rolled Ring Forgings
- ASTM B594 – Ultrasonic Inspection of Aluminum-Alloy Wrought Products
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- ASM Handbook, Vol. 2 – Properties and Selection: Nonferrous Alloys and Special-Purpose Materials
6151 aerospace forgings: frequently asked questions
What is the difference between 6151 and 6061 forgings?
6151 has more silicon and a narrower magnesium range plus chromium, which make it flow better into complex dies and give a finer grain. Strength in T6 is similar, with 6151 slightly higher in typical data.
Which specification covers 6151 aerospace forgings?
SAE AMS 4125 covers 6151-T6 die forgings, rolled or forged rings and forging stock. ASTM B247 also includes 6151 for commercial and general forgings.
Is 6151 available in T651 or T74?
Not normally. The standard forging tempers are T6 and T652 (compression stress-relieved). T651 is a stretched temper for plate and bar, and T74 belongs to 7xxx alloys.
Is 6151 suitable for marine or corrosive environments?
Yes. With low copper and a chromium addition, 6151-T6 has very good general and stress-corrosion resistance, and anodising adds further protection.
Do you supply forgings to our own drawing?
Yes. Send the drawing with the specification, test requirements and quantity, and we will propose a forging route and confirm the certification package.
Need 6151 aerospace forgings?
Send the drawing, temper, specification and quantity. We will reply with the forging route, certification and a delivered price.
