Aluminium Die Forgings for Chassis, Housings and Structural Parts

What is an aluminium die forging?

In closed-die (impression-die) forging, a heated aluminium billet is pressed between an upper and a lower die that together hold the negative shape of the part. The metal flows to fill the cavity, a thin flash escapes at the parting line and is trimmed off, and the forging is then heat treated and machined where needed.

Three things make a die forging different from the alternatives. First, the deformation closes any internal voids, so there is none of the gas or shrinkage porosity that limits castings. Second, the grain structure is stretched and aligned along the outline of the part, so ribs, bosses and lugs carry load along the grain rather than across it. Third, the part comes out near net shape, so a forging that would need 70 % of a plate blank machined away often needs only a few millimetres per face.

The trade-off is tooling. A set of forging dies is a real investment, and each new shape needs its own. Die forging therefore makes most sense for repeat parts, safety-critical parts and parts where weight matters enough to justify the die cost. For one-off or very low quantities, a hand (open-die) forging or forged block machined to shape is usually the better route.

The aluminium closed-die forging route

1. Forging stockCast and homogenised billet or extruded bar is sawn to a calculated weight. Extruded stock gives finer, more uniform grain for small, thin-walled parts.
2. PreheatingStock is heated in a controlled furnace, commonly about 430 – 480 °C for 6061 and 6082 and about 380 – 440 °C for 7075. Aluminium has a narrow forging window, so temperature control is essential.
3. Heated diesUnlike steel forging, the dies are preheated (often a few hundred degrees Celsius on hydraulic presses) so the metal does not chill and crack on contact.
4. Blocker and finisherComplex parts are pre-shaped in a blocker die, then completed in a finisher die. Hydraulic presses are preferred for aluminium because slower strain rates help the metal fill deep ribs.
5. TrimmingFlash is trimmed and the part is cleaned, deburred and visually inspected.
6. Heat treatmentSolution treatment, quench and ageing to T6, T73 or another temper; T652 or T7352 add cold compression to relieve quench stress.
7. FinishingShot blasting, machining of functional faces and holes, inspection, and surface treatment as specified.

Alloys used for aluminium die forgings

Most die forgings are made in a handful of alloys. The table compares them by what usually decides the choice.

In automotive chassis work, 6082-T6 has largely become the default because it combines good strength with corrosion resistance and stable forging behaviour. 6061-T6 is the general-purpose alternative, especially for markets that work to ASTM rather than EN standards. For alloy-specific detail see our 6061, 2024 and 7075 forging pages.

Mechanical properties of common die-forging alloys

Typical values for each alloy and temper are shown for comparison. Guaranteed minimums for forgings are lower, vary with section thickness and test direction, and are set by the order specification (ASTM B247, EN 586-2, AMS or a customer standard).

For reference, ASTM B247 longitudinal minimums for 6061-T6 die forgings are 262 MPa (38 ksi) tensile and 241 MPa (35 ksi) yield with 7 % elongation. Always design to the specification minimum, not the typical value.

Design guidelines for aluminium die forgings

Good forging design lowers die cost, reduces machining and improves properties. These are general guidelines; we review every drawing before quoting and suggest changes where they help.

Typical aluminium die-forged parts

Die forgings by industry

A typical case is a cast suspension arm being redesigned as a forging: the forged 6082-T6 version can use thinner sections because there is no porosity to allow for, often saving a meaningful share of the weight while improving fatigue life. Another common case is a hydraulic manifold where castings leak through porosity after machining; a forged 6061-T6 block removes that failure mode.

Tolerances, testing and certification

Die-forging dimensional tolerances depend on size, weight and complexity. ANSI H35.2 gives standard tolerances for aluminium die forgings (length, width, thickness, die closure, mismatch, flash extension, straightness and flatness); tighter values are agreed on the drawing for machined features.

Die forging compared with casting, machining and open-die forging

If the volume is too low for dies, a forged block or forged bar machined to shape keeps most of the material benefit. For round parts, a forged disc or rolled ring is often cheaper than a dedicated die.

Related forgings and guides

How to order aluminium die forgings

1. Send the designDrawing or 3D model with machined and as-forged surfaces marked, alloy and temper, annual and batch quantity.
2. Forging reviewWe propose the parting line, draft, machining allowance and heat-treatment route, and flag features that raise die cost.
3. Tooling and samplesDies are made and first articles forged for dimensional, mechanical and grain-flow approval.
4. Series productionForging, heat treatment, machining and inspection to the agreed control plan.
5. Documents and shippingEN 10204 3.1 certificate and inspection reports; export packing with corrosion protection; EXW, FOB, CIF or DAP.

Aluminium (aluminum) die forgings: frequently asked questions