Aluminium Forgings for Vehicle Powertrain, Chassis & Structure

Why vehicles use forged aluminium

Forging squeezes a heated aluminium billet between shaped dies until it fills the cavity. Unlike casting, the metal never melts, so there is no shrinkage porosity, and the grain flow follows the contour of the part. That continuous grain flow is what gives forged knuckles, control arms and connecting rods their high fatigue life and impact toughness.

A forged aluminium lower control arm typically weighs around half as much as a stamped or forged steel arm with the same stiffness target. Because suspension parts are unsprung mass, every kilogram saved improves ride, grip and steering response more than the same saving in the body. For electric vehicles the gain is doubled: lighter chassis parts offset battery mass and add range.

Forging also suits the safety logic of the automotive industry. A forged part has predictable, near-isotropic properties along its load paths, it can be ultrasonically inspected, and it fails by yielding rather than by sudden fracture from an internal void. That is why steering, braking and wheel-carrying parts are forged far more often than cast when they are made from aluminium.

Forging alloys and their properties

Most automotive forgings are made from heat-treatable alloys, because only solution treatment and ageing give the strength that steel-replacement parts need. The table shows minimum or typical values for die forgings; actual minimums depend on section thickness and are set by the specification on your drawing.

Minimums for 6061, 2014, 2618 and 7075 follow ASTM B247 die-forging values for sections up to about 100 mm; 6082 follows EN 586-2. Typical values are for information only and are not design guarantees.

For aluminium the physical constants barely change between alloys: density is 2.68 – 2.80 g/cm³ (about one third of steel), elastic modulus about 69 – 72 GPa, and thermal conductivity 120 – 170 W/m·K, which helps brake and engine parts shed heat. The lower modulus means aluminium parts are designed with deeper sections than the steel parts they replace; good forging design puts that extra depth exactly where stiffness is needed.

Forgings in the engine: heat and cyclic load

Engine parts see high temperature and millions of load reversals. Only a few aluminium alloys keep useful strength above 150 °C, which narrows the choice quickly.

Crankshafts, camshafts and gear teeth stay in steel in volume engines because no aluminium alloy matches steel on contact fatigue and wear at those loads. Where an older specification lists aluminium for such parts, it usually means a housing, carrier or support ring around the steel part rather than the shaft itself.

Chassis, suspension and brake forgings

This is the largest market for automotive aluminium forgings. Suspension and steering parts need high yield strength, fatigue resistance under road load spectra, and corrosion resistance against road salt, often with no paint on internal surfaces.

A typical premium-car front axle uses forged 6082 or 6061 for both control arms and the knuckle. The parts are forged from extruded or continuously cast bar, solution treated, quenched, aged to T6, shot-peened in high-stress areas and machined. Alloys with added manganese and chromium are chosen because they keep a fine, unrecrystallised grain structure after forging, which raises fatigue strength and resistance to intergranular corrosion.

Driveline, body-structure and EV drive forgings

Electric drive units run their motors at 15,000 – 20,000 rpm or more, so balance, dimensional stability after machining and freedom from internal defects matter more than peak strength. Forgings in T6 that have been stress-relieved or rough-machined before final ageing hold their shape best.

Design and processing considerations

1. Forging stockExtruded bar is the usual feed; continuously cast bar can give a finer, more uniform grain in 6082 and lower cost. Billet must be free of coarse grain rings that would end up at the surface.
2. Forging temperature6xxx alloys are typically forged at about 430 – 500 °C, 2xxx at 420 – 460 °C and 7xxx at 380 – 440 °C, with dies preheated to limit chilling.
3. Heat treatmentSolution treatment, quench (often into polymer or warm water to reduce distortion) and artificial ageing to T6, T61 or T73, per AMS 2770 or the customer process.
4. FinishingTrimming, shot peening of high-stress zones, CNC machining of bores and faces, and anodising, e-coating or conversion coating.
5. InspectionGrain-flow macro-etch on first articles, ultrasonic testing, penetrant or eddy-current crack testing, hardness and conductivity checks, and tensile tests from prolongations.

• Draft and radii: allow 3 – 7° draft and generous fillet radii; sharp corners cause laps and cold shuts.
• Parting line: place it where flash can be trimmed without cutting across the main grain flow.
• Galvanic contact: isolate steel bushings, studs and ball joints from aluminium with coatings or sleeves.
• Stress corrosion: specify T73 or T7451 rather than T6 for 7xxx parts that carry sustained tensile stress.

Standards, approvals and documentation

Automotive buyers typically ask for first-article inspection, a PPAP or equivalent submission, process capability on critical dimensions and full lot traceability from cast bar to finished part. Metline works under an ISO 9001 quality system and ships each lot with an EN 10204 3.1 mill test certificate; we coordinate third-party inspection where your approval process needs it.

Forging forms we supply

Prototype quantities are often machined from forged blocks or bars of the same alloy to validate the design before die tooling is cut. Tell us at the enquiry stage whether you need rough forgings, heat-treated forgings or machined parts.

Related alloys, forms and applications

Automotive aluminium (aluminum) forgings: FAQ