A custom aluminium forging is a part shaped by pressing or hammering hot aluminium to a drawing, so that the metal's grain follows the part's contour and the finished component is stronger and more fatigue-resistant than one machined from plate or cast in a mould. This guide helps engineers and buyers choose between open-die, closed-die and ring-rolled forgings, pick the alloy and temper, design a part that forges well, and write a request for quotation that gets accurate answers. Metline supplies aluminium forgings to drawing, as forged or machined, to customers worldwide.
Forging works the metal under compressive force. It closes internal porosity, breaks up the cast structure of the starting billet and aligns the grain along the shape of the part. The result is the highest and most consistent combination of strength, ductility and fatigue resistance available in a given aluminium alloy.
Compared with machining the same shape from thick plate or bar, a forging puts the grain flow where the loads are. In a machined part, the grain of the plate runs straight and is cut through at every curve, so fillets and lugs end up loaded across the weakest (short-transverse) direction. In a forging the grain wraps around the curve. This matters most for parts loaded in fatigue, such as suspension arms, wheels, landing-gear fittings and rotating components.
Compared with a casting, a forging has no shrinkage porosity, a finer grain and much higher elongation. Castings win on complex internal cavities and on cost for low-stress parts; forgings win wherever the part is safety-critical or cyclically loaded. Forging also usually saves material compared with machining from a solid block, because the shape is close to final dimensions before machining starts.
| Route | Strength and fatigue | Shape freedom | Material use | Tooling | Best quantity range |
|---|---|---|---|---|---|
| Closed-die forging | Highest, grain follows contour | Good, with draft and fillets | Efficient (near net) | Dies required | Hundreds to many thousands |
| Open-die forging | High, grain worked in one or two directions | Simple shapes | Moderate, more machining | Generic tools | One-off to a few hundred |
| Machined from plate or bar | Good, but grain cut at contours | Any machinable shape | Wasteful for large parts | None | Prototypes, low quantities |
| Casting | Lower, porosity possible | Highest, internal cavities | Efficient | Moulds or patterns | Medium to very high |
The billet is shaped between flat or simple dies, turned and worked by the operator. It produces blocks, discs, bars, shafts and hollow cylinders with generous machining allowance. No dedicated tooling, so it is the economical route for large parts, prototypes and small batches. See forged blocks and forged discs.
Hot metal fills a machined die cavity, often in several stages (blocker then finisher), and excess flows into a flash that is trimmed off. Produces near-net shapes such as control arms, brackets, knuckles and housings with repeatable dimensions. Die cost is paid back over volume. See aluminium die forgings.
A pierced, forged doughnut is rolled between a driven roll and an idler, growing in diameter while the wall thins. Gives seamless rings with circumferential grain flow for flanges, bearing races, slewing rings and wheel rims. See rolled ring forgings.
A punch drives into a billet held in a container so metal flows back around it, forming cups, cylinders and thick-walled tubes with a closed end. Used for housings, valve bodies and pressure vessel parts.
Closed-die forging with tighter tolerances, little or no draft and thin webs, reducing machining. Higher die and press cost; used for aerospace and high-volume automotive parts. See precision forgings.
Forming at room temperature or moderately elevated temperature for small parts that need tight tolerances and good surface finish, typically in softer alloys such as 1xxx, 3xxx and 6xxx. See aluminium cold forging.
A useful rule of thumb: if you need fewer than a few dozen parts, or the part is large and simple, start with open-die forgings and machine to shape. Once quantities justify a die, closed-die forging reduces weight, machining time and material cost per part. Rings and annular parts above a few hundred millimetres in diameter are almost always ring-rolled.
Aluminium alloys have a narrow hot-working window compared with steel. Most wrought alloys are hot forged with the metal at roughly 350 – 500 °C, and dies are heated as well (often 150 – 450 °C depending on process) so that the thin aluminium sections do not chill and crack on contact. Too hot, and the alloy can melt at grain boundaries (incipient melting); too cold, and it cracks or fails to fill the die.
| Route | Typical metal temperature | Characteristics | Typical parts |
|---|---|---|---|
| Hot forging | About 350 – 500 °C, alloy dependent | Low forming force, large deformation, recrystallised grain; followed by heat treatment | Large blocks, rings, shafts, structural die forgings |
| Warm forging | Below the hot range, above room temperature | Better dimensional control than hot, less force than cold | Small and medium structural parts, flanges |
| Cold forging | Room temperature | Tight tolerances, fine finish, work-hardened surface; limited to ductile alloys and small parts | Connectors, fastener blanks, small shafts, impact-extruded housings |
Exact forging and die temperatures are set by the forging shop for each alloy; 2xxx and 7xxx alloys have narrower windows than 6xxx alloys.
Most aluminium forgings are made from heat-treatable alloys, which are forged, solution heat-treated, quenched and aged to their final strength. Non-heat-treatable 5083 is used where weldability and seawater resistance matter more than strength. The table compares typical properties; specified minimum values depend on the forging type (die, hand or rolled ring), the thickness and the test direction, and are set by ASTM B247, EN 586-2 or the relevant AMS specification.
| Alloy and temper | Typical tensile strength | Typical yield strength | Key traits | Typical forged parts |
|---|---|---|---|---|
| 6061-T6 | 310 MPa | 276 MPa | Good strength, corrosion resistance and weldability; easy to forge | Brackets, flanges, wheels, fittings, general structural parts |
| 6082-T6 | 310 – 340 MPa | 260 – 300 MPa | European structural alloy, slightly stronger than 6061 in thick sections | Automotive suspension parts, rail and machinery components |
| 5083-O / H111 | 290 MPa | 145 MPa | Not heat-treatable; excellent seawater resistance and weldability | Marine fittings, cryogenic flanges, welded structures |
| 2014-T6 | 483 MPa | 414 MPa | High strength, good machinability; needs corrosion protection | Aerospace fittings, heavy-duty truck parts, hydraulic components |
| 2618-T61 | 440 MPa | 370 MPa | Retains strength at elevated temperature | Pistons, compressor wheels, engine parts |
| 4032-T6 | 380 MPa | 315 MPa | High silicon gives low expansion and wear resistance | Forged pistons, compressor components |
| 7075-T6 | 572 MPa | 503 MPa | Very high strength; lower stress-corrosion resistance in T6 | Aerospace and motorsport parts, high-stress fittings |
| 7075-T73 | 505 MPa | 435 MPa | Over-aged for much better stress-corrosion resistance | Aircraft fittings, landing-gear parts |
| 7050-T74 | Higher than 7075-T73 in thick sections | — | Less quench-sensitive than 7075, good toughness and SCC resistance | Thick aerospace forgings, bulkheads, frames |
Typical room-temperature values from Aluminum Association and ASM data, for comparison only. Designs should use the specified minimums of the governing standard, and every forging lot is certified with its own test results.
As a starting point: choose 6061 or 6082 for general engineering and automotive parts, 5083 for marine and welded parts, 2014 for high-strength machined parts that will be protected from corrosion, 2618 or 4032 for heat and wear, and 7075-T73 or 7050-T74 for aerospace-grade strength with stress-corrosion resistance. Alloy-specific pages: 6061 forgings, 7075 forgings and 2024 forgings.
| Temper | Meaning | When to specify |
|---|---|---|
| F | As forged, no heat treatment | Forging blanks that the buyer will heat-treat after rough machining |
| O | Annealed | Maximum ductility for further forming; rarely the final condition |
| T4 | Solution treated and naturally aged | Intermediate condition, for parts formed or straightened before ageing |
| T6 / T61 | Solution treated, quenched, artificially aged | Standard high-strength condition for 2xxx, 4xxx, 6xxx and 7xxx forgings |
| T652 | T6 with compressive stress relief (1 – 5 % permanent set) before ageing | Hand forgings and blocks that will be heavily machined, to reduce distortion |
| T73 / T7352 | Over-aged for maximum stress-corrosion resistance; T7352 adds stress relief | 7075 parts in aerospace and other corrosive or sustained-load service |
| T74 / T7452 | Over-aged, between T6 strength and T73 corrosion resistance | 7050 and 7075 aerospace forgings |
Quenching after solution treatment leaves residual stresses, especially in thick forgings, which can cause parts to move during machining. Stress-relieved tempers (T652, T7352, T7452) are produced by a controlled cold compression after quenching and are the right choice for blocks and hand forgings that will have large amounts of metal removed. Quench sensitivity also limits the section thickness that reaches full properties: 7050 and 2xxx alloys hold their strength in thicker sections better than 7075 or 6061.
Small design choices drive die life, material use and cost. Involve the forging supplier early, ideally while the drawing is still flexible.
Place the parting line at the largest cross-section so the part releases from both die halves. A flat parting line is cheaper than a stepped one.
Conventional closed-die aluminium forgings typically use about 5 – 7° draft on external surfaces, more on deep internal pockets. Precision forgings can reduce this, at higher tooling cost.
Generous radii help metal flow and prevent laps and folds. Sharp internal corners concentrate stress and shorten die life.
Aluminium forges thinner ribs and webs than steel, but very thin webs over large areas cool quickly and need high press force. Keep rib height to width ratios moderate.
Allow stock on surfaces that need tight tolerance or fine finish, typically a few millimetres per face on die forgings and more on open-die forgings. Leave forged surfaces as-forged where function allows.
Orient the part so the principal loads run along the grain. Ask for a macro-etch grain-flow check on first articles of critical parts.
Define machining datums on forged surfaces that are stable and easy to locate, and mark them on the forging drawing.
Use standard forging tolerances (for example EN 586-3 or the supplier's tables) unless a feature truly needs tighter control; then machine it.
If the forging will be welded, choose 6xxx or 5083 and keep welds away from the most highly stressed areas, because the heat-affected zone loses strength.
Forgings are often used precisely because they are critical parts, so the inspection plan should be agreed at the quotation stage, not after the parts arrive.
| Check | Purpose | Typical reference |
|---|---|---|
| Chemical analysis | Confirms the alloy | EN 573-3, Aluminum Association limits |
| Tensile tests | Verifies strength and elongation in specified directions | ASTM B557, ISO 6892-1 |
| Hardness and conductivity | Quick check of heat treatment on every part | ASTM E10 (Brinell), ASTM E1004 (eddy-current conductivity) |
| Ultrasonic testing | Finds internal discontinuities | ASTM B594, AMS-STD-2154 (classes AAA to B) |
| Penetrant testing | Detects surface laps, folds and cracks | ASTM E1417 |
| Macro-etch / grain flow | Confirms grain follows the contour on first articles | Agreed with the customer |
| Dimensional inspection | Confirms forged and machined dimensions | Drawing, CMM report on request |
| Documents | Traceability | Mill test certificate to EN 10204 3.1, heat treatment records, NDT reports, certificate of conformance |
Forgings delivered in the specified temper with forged surfaces, for the buyer's own machining. Lowest unit price and the most control for the buyer.
Forged, heat-treated and rough machined to remove the skin and establish datums, often after ultrasonic inspection. Reduces scrap risk on the buyer's finish-machining line.
Forged, heat-treated and fully CNC machined to the part drawing, with surface treatment such as anodising, hard anodising or painting if specified. Ready for assembly.
Machining forgings is a specialist job: residual stresses must be balanced by removing metal evenly from opposite faces, and datum choices affect final flatness. Our CNC aluminium machining guide covers what to specify.
| Industry | Typical forged parts | Common alloys |
|---|---|---|
| Aerospace and defence | Wing and fuselage fittings, frames, landing-gear components, wheels, actuator housings | 2014, 2219, 7050, 7075-T73 |
| Automotive and commercial vehicles | Control arms, steering knuckles, wheels, brake caliper brackets, connecting rods | 6061, 6082, 7075 |
| Rail | Bogie components, coupling parts, brackets | 6082, 6061 |
| Marine and offshore | Deck fittings, flanges, cryogenic LNG valve and flange parts | 5083, 6061, 6082 |
| Energy and fluid control | Valve bodies, pump housings, flanges, slewing rings | 6061, 6082, 2014 |
| Industrial machinery | Rotating discs, hubs, shafts, fixture bases | 6061, 2014, 7075 |
| Sports and recreation | Bicycle cranks and stems, climbing hardware, motorsport parts | 6061, 7075 |
Example: a typical commercial-vehicle control arm is closed-die forged in 6082, heat-treated to T6, shot peened to improve fatigue life and machined only at the bushing bores and ball-joint seat. A typical cryogenic flange for LNG service is ring-rolled from 5083 and machined, because 5083 keeps its toughness at very low temperature and can be welded to 5083 pipe.
In the same alloy and temper, a forging usually has better fatigue strength, toughness and ductility in critical areas because its grain follows the part shape and internal porosity has been closed. Static strength in the main direction is similar; the advantage is consistency and performance at fillets and lugs.
Open-die forging shapes metal between simple tools and suits large, simple shapes and small quantities. Closed-die forging fills a machined die cavity to produce near-net shapes, with tooling cost that pays back over larger quantities.
6061 and 6082 are the easiest and most common for general parts. 2014 and 7075 give higher strength, 7050 is preferred for thick aerospace sections, 5083 for marine and cryogenic parts, and 2618 or 4032 for high-temperature pistons.
T73 is over-aged, which sacrifices some strength (typically around 10 – 15 %) for much better resistance to stress-corrosion cracking. It is the normal choice for aerospace fittings and parts under sustained load in humid or marine air.
Yes. Forgings can be supplied as forged, rough machined or fully machined with surface treatment, together with mill test certificates and inspection reports as agreed in the order.
ASTM B247 is the general US standard for die, hand and rolled ring forgings; EN 586 covers forgings in Europe; AMS-A-22771 and alloy-specific AMS specifications apply to aerospace parts. Ultrasonic testing is often specified to ASTM B594 or AMS-STD-2154.
It depends on whether new dies are needed, the alloy and heat treatment, testing requirements and machining scope. Open-die parts are generally faster to start than closed-die parts that need tooling. Share your drawing and quantity for a confirmed schedule.
Send your drawing, alloy and temper, quantities and test requirements. Our team will review the design and reply with a supply route, documents and delivered price.
