2618 aluminum is a high-temperature alloy, and temperature is the whole reason to specify it. It is a heat-treatable Al-Cu-Mg alloy with iron and nickel added, developed for forged parts that run hot: pistons, compressor wheels, engine components. It holds its strength at temperatures where 2024 그리고 7075 have already given most of theirs away.
That makes it a specialist buy rather than a general-purpose one. It costs more than a 6xxx, it corrodes more readily, and it is not the grade you reach for when the part runs cool.
What Is 2618 Aluminum?
2618 is a heat-treatable 2xxx alloy built for one job: holding strength when the part gets hot. Its copper and magnesium supply the room-temperature strength the 2xxx family is known for. Its iron and nickel are what stop that strength collapsing at temperature.
Iron and nickel work as a pair. In roughly equal amounts they form Al₉FeNi particles that do not dissolve at service temperature, so they pin the grain boundaries while the copper–magnesium precipitates do the strengthening. That pairing is why 2618 is a piston and engine alloy rather than a structural plate alloy.
It is also a low-silicon grade, 0.25% maximum. That is what separates it from 4032, which carries 11–13.5% silicon. Low silicon gives 2618 more ductility and better tolerance of detonation; high silicon gives 4032 lower thermal expansion and far better wear resistance. Neither is better in general — they answer different failure modes.
2618 Aluminum Composition
2618 is specified by chemistry before anything else, because the iron and nickel levels are what make the grade. These are the ASTM B247 limits for 2618:
| 요소 | Limit (%) | Why it is there |
|---|---|---|
| 구리 | 1.9–2.7 | Strengthening after heat treatment |
| 마그네슘 | 1.3–1.8 | With copper, forms the hardening precipitates |
| 니켈 | 0.9–1.2 | With iron, forms the heat-stable particles |
| Iron | 0.9–1.3 | The other half of that pair |
| 실리콘 | 최대 0.25 | Kept low for ductility |
| 티타늄 | 0.04–0.10 | Grain refinement during forging |
| 아연 | 최대 0.10 | 불순물 |
| 알루미늄 | 잔액 |
EN AW-2618A is not identical to the ASTM grade. The European limits allow more nickel and iron (0.8–1.4% Ni, 0.9–1.4% Fe) and require at least 0.15% silicon, so name the standard you are buying to. Whatever the heading says, iron and nickel are the rows to check on the mill certificate.
Tempers: T61 for Forgings, T851 for Plate
Most 2618 in service is T61. It is solution treated, quenched in boiling water, then aged at 182–187 °C for about 20 hours. The boiling-water quench is deliberate: it cools slowly enough to keep residual stress and distortion down in a forged shape, at the cost of a little peak strength.
Plate is usually supplied as T851 — solution treated, stress-relieved by stretching, then artificially aged. The stretch is what holds a plate flat through machining, and it is also why plate carries lower guaranteed values than a forging of the same alloy: roughly 420 MPa tensile at 6–40 mm, easing to about 395 MPa at 100–140 mm.
Either way the temper belongs on the purchase order rather than in a note. T6, T61 and T851 are not interchangeable, and the certificate has to name the one the part was designed around.
기계적 및 물리적 특성
Typical values for 2618-T61:
| 속성 | 가치 |
|---|---|
| 인장강도 | ~440 MPa |
| 항복 강도(0.2%) | ~370 MPa |
| 신장 | ~10% |
| 경도 | ~115–120 HB |
| 밀도 | 2.75g/cm³ |
| Modulus | ~73 GPa |
| 용융 범위 | ~549–638 °C |
| 열 전도성 | ~146 W/m·K |
| 열팽창 | ~22 ×10⁻⁶/°C |
These are hand-forging figures in the longitudinal direction. Die forgings run lower — around 400 MPa tensile and 310 MPa yield on an axial test — and short-transverse sections lower still, so a part loaded across the grain needs the softer numbers.
How Well Does 2618 Hold Strength at High Temperature?
This is the question the grade exists to answer, so it is worth putting the numbers on it. Typical 2618-T61 tensile strength at temperature:
| 온도 | 인장강도 | Share of room-temperature strength |
|---|---|---|
| 24 °C | 441 MPa | 100% |
| 100 °C | 427 MPa | 97% |
| 149 °C | 345 MPa | 78% |
| 204 °C | 221 MPa | 50% |
| 260 °C | 90 MPa | 20% |
Read it this way: 2618 keeps most of its strength to about 150 °C, still carries roughly half at 200 °C, and falls away quickly above that. It is not a 300 °C alloy. What it does better than 2024 or 7075 is lose strength more slowly through the 150–200 °C band, which is exactly where a piston crown or a compressor wheel sits.
Where 2618 Is Used
Forged pistons. This is the volume application. 2618 was developed as a forging alloy, it fills a complex piston shape well, and it keeps its strength where the crown actually runs. Racing and high-boost engines specify it for those reasons.
Aircraft engine and compressor parts. Pistons, compressor wheels, impellers and rotating components where the part is hot for its whole life and fatigue matters as much as static strength.
Motorsport and defense. The same logic as pistons, applied to con-rods, cylinder heads and structural parts that see repeated thermal cycling.
2618 vs 4032 vs 2024 vs 6061 vs 7075
| 합금 등급 | 2618-T61 | 4032-T6 | 2024-T3 | 6061-T6 | 7075-T6 |
|---|---|---|---|---|---|
| 주요 합금 원소 | Cu, Mg, Fe, Ni | Si 11–13.5% | Cu, Mg | Mg, Si | 아연, 구리, 마그네슘 |
| 인장강도 | ~440 MPa | 370–415 MPa | ~470 MPa | ~310 MPa | ~570 MPa |
| 항복강도 | ~370 MPa | 315–350 MPa | ~325 MPa | ~276 MPa | ~505 MPa |
| 밀도 | 2.75g/cm³ | 2.69g/cm³ | 2.78g/cm³ | 2.70g/cm³ | 2.81g/cm³ |
| 열팽창 | ~22 ×10⁻⁶/°C | ~19.4 ×10⁻⁶/°C | ~23 ×10⁻⁶/°C | ~23.6 ×10⁻⁶/°C | ~23.6 ×10⁻⁶/°C |
| Hot strength | Best of the five | Good to ~200 °C | Falls away above 150 °C | ~150°C | ~120 °C |
| 내식성 | 열악함에서 공정함 | 보통 | Poor | 매우 우수 | 공정 |
| 용접성 | 권장되지 않음 | Poor | 공정 | 우수 | Poor |
The table reads as trade-offs rather than a ranking. 7075 is the strongest at room temperature and the wrong choice for a hot part, 6061 is the easiest to weld, finish and afford and the weakest of the five, and 2024 beats 2618 cold but loses to it hot. 4032 is the only grade here that competes with 2618 for the same job.
That choice turns on expansion. 4032’s 19.4 ×10⁻⁶/°C buys a tighter cold clearance and less piston slap; 2618’s ~22 ×10⁻⁶/°C costs some of that and buys tolerance to detonation plus better fatigue life. Street builds usually take 4032 and boosted builds usually take 2618 — our 4032 aluminum guide covers the other side.
When to Specify 2618 — and When Not To
Specify 2618 when the part is forged, sees sustained service above about 150 °C, and the design case includes thermal fatigue or detonation. It is also the right call when the alternative is a steel part that is too heavy.
Do not specify 2618 when the part runs below about 120 °C — 2024 or 7075 will give you more strength for less money. It is also the wrong choice for anything welded, for anything that lives in chloride or splash-zone service without a coating, and for a part whose shape is better extruded than forged.
Machining, Welding and Corrosion
절삭 가공. 2618 machines well in T61: short chips, good finishes, and no built-up-edge trouble at sensible parameters. It has no free-machining additions, so sharp tooling and adequate coolant still matter.
용접. Fusion welding is not recommended. Copper, iron and nickel segregate in the weld pool, which brings hot-cracking risk and a joint far weaker than the parent metal. Fasten or bond instead. Where welding is unavoidable, TIG with controlled heat input followed by a re-age is the least bad route.
부식. Copper makes this a poor-to-fair alloy in corrosion terms, well behind a 6xxx. It is fine indoors and in oil or fuel environments; it needs anodizing or a coating outdoors, and it should be isolated from steel fasteners to avoid galvanic attack.
Standards and What to Put on the Purchase Order
2618 appears in ASTM B247 for forgings and AMS 4132 for aerospace forgings, with EN AW-2618A covering the European equivalent and GB/T 3190 listing the Chinese near-equivalent 2A70. Older drawings may carry the designation RR58.
A complete line item names the alloy and temper, the governing standard, the product form, the grain direction if the part is stressed across it, and the test certificates required. Iron and nickel should be checked against the certificate on receipt, because that pair is the grade.
결론
2618 is a high-temperature forging alloy rather than a general-purpose one. It keeps most of its strength to about 150 °C, still carries half at 200 °C, and it costs more and needs more corrosion protection than a 6xxx in return.
당사는 공급함 2618 알루미늄 as sheet, plate, tube, bar and forgings, quoted to ASTM B247 or EN AW-2618A, with an MTC on every order.
Send the drawing, the temper and the service temperature, and we will confirm the form and the values behind it.
자주 묻는 질문
Is 2618 the same as 2A70 or 2618A?
No — they are close relatives, not interchangeable designations. 2A70 is the Chinese near-equivalent under GB/T 3190, and EN AW-2618A is the European grade with looser nickel and iron limits. If a drawing names one of them, buy to that standard rather than substituting on the basis of a cross-reference table.
Does 2618 come as sheet and plate, or only as forging?
All of those forms are supplied, and the form usually decides the temper. Forged stock runs T61, plate is normally T851 so it stays flat through machining, and lighter sheet and tube come in the aged tempers. Tell us the form and finished thickness and we will confirm what is stocked.
Why does 2618 cost more than 6061?
Three things add cost: expensive alloying additions, a slow quench-and-age cycle, and low volume. The grade serves a narrow set of applications, so it never runs at 6061 volumes. The premium buys strength that survives heat, which 6061 cannot offer at any price.
What is the minimum order quantity for 2618?
Stocked bar and plate ship from standard pack quantities. Anything outside the stocked range — a non-standard thickness, a forging, or a specific temper — runs as a low-MOQ custom order with a typical lead time of 10–60 days. Send the form, temper and size and we will confirm what ships from stock.
