Closed-die forgings
Near-net shapes for impellers, fittings and frames, with grain flow following the part contour.
Heat-resistant forgings
2A70 Aerospace Aluminium Forgings
2A70 is the heat-resistant forging alloy of the Chinese GB system and the close counterpart of 2618: iron and nickel additions let forgings keep their strength at 150 – 250 °C. It is used for compressor impellers, engine parts and hot-running airframe fittings. Metline supplies 2A70-T6 die and free forgings to HB 5204 and GJB 2351, worldwide.
- Alloy
- 2A70 (formerly LD7)
- Temper
- T6
- Standards
- HB 5204 · GJB 2351
- Western counterpart
- 2618 / 2618A
What 2A70 is
2A70, formerly LD7, combines copper and magnesium for age-hardening with about 1.2 % each of iron and nickel. The iron and nickel form Al9FeNi intermetallic particles that remain stable at temperature, so 2A70 forgings resist softening and creep far better than 2A50 or 2A14 forgings.
Its chemistry closely matches 2618, and the two are generally treated as counterparts. Typical parts are compressor impellers, fans and rotors in aero engines and auxiliary power units, pistons, and airframe fittings exposed to engine heat or aerodynamic heating.
A well-known example of the alloy's capability is the closed-die forged impeller or rotor with many thin, twisted radial blades: such parts demand an alloy that fills fine die detail during forging and then holds strength and fatigue resistance in hot, high-speed rotation.
2A70 chemical composition (wt %)
Limits per GB/T 3190, shown with 2618 for comparison.
| Element | 2A70 (GB) | 2618 (AA) |
|---|---|---|
| Copper (Cu) | 1.9 – 2.5 | 1.9 – 2.7 |
| Magnesium (Mg) | 1.4 – 1.8 | 1.3 – 1.8 |
| Iron (Fe) | 0.9 – 1.5 | 0.9 – 1.3 |
| Nickel (Ni) | 0.9 – 1.5 | 0.9 – 1.2 |
| Silicon (Si) | 0.35 max | 0.10 – 0.25 |
| Manganese (Mn) | 0.20 max | — |
| Zinc (Zn) | 0.30 max | 0.10 max |
| Titanium (Ti) | 0.02 – 0.10 | 0.04 – 0.10 |
| Others each / total | 0.05 / 0.10 | 0.05 / 0.15 |
| Aluminium | Remainder | Remainder |
Mechanical properties of 2A70-T6 forgings
| Standard and form | Rm (L, LT, ST) | A5 | Hardness |
|---|---|---|---|
| GJB 2351, free and die forgings | ≥ 375 MPa | ≥ 4 % | ≈ 110 HBS |
| HB 5204, free forgings | ≥ 375 MPa | ≥ 5 % | ≈ 110 HBS |
| HB 5204, die forgings | ≥ 380 MPa | ≥ 5 % | ≈ 110 HBS |
Minimum values as commonly quoted from GJB 2351 and HB 5204 for forgings of typical section; limits depend on section thickness and the standard revision. The ordered standard and certificate govern.
Typical properties are similar to 2618-T61: about 440 MPa tensile and 370 MPa yield at room temperature. Data for 2618 shows roughly 345 MPa tensile strength retained after 10,000 hours at 150 °C and about 220 MPa at 205 °C, which is a reasonable guide to 2A70 behaviour; use programme data for design.
Physical data (approximate)
- Density
- about 2.80 g/cm³
- Melting range
- roughly 550 – 640 °C
- Thermal conductivity
- about 145 W/m·K
2A70 forging types
Open-die (free) forgings
Blocks, discs and stepped shapes for machining, used for prototypes and low volumes.
Rings and discs
Upset and ring-rolled blanks for rotating and casing parts.
Forged bar
Round and square forged bar for heavy machined components.
Forgings are produced through qualified forging partners to your drawing. Achievable size and weight depend on the forging route and heat-treatment equipment, so feasibility is confirmed for each drawing rather than quoted from a generic table.
Forging, heat treatment and machining
- Forging: billets are heated to the upper part of the forging range; the alloy's good thermal conductivity helps uniform heating.
- Heat treatment: solution treatment around 525 – 535 °C, quench, and artificial ageing around 180 – 200 °C to T6.
- Machining: good, with slightly higher tool wear from Fe-Ni particles; carbide tools recommended.
- Joining: not intended for fusion welding; use mechanical joints.
- Surface protection: anodising or conversion coating and paint.
- Inspection: ultrasonic testing, macro-etch grain-flow checks and conductivity/hardness checks are common.
Applications of 2A70 forgings
- Aero engines: compressor impellers, fans, rotors and casings that run warm
- Missile and APU engines: closed-die forged rotors with thin twisted blades
- Pistons: high-load pistons where 2618-type alloys are specified
- Airframe: fittings, brackets and frames near engines or in heated zones
- Flight-control hardware: levers and fittings in warm areas
2A70 compared with 2A80, 2A50 and 2618
| Factor | 2A70 | 2A80 | 2A50 | 2618 |
|---|---|---|---|---|
| Heat resistance | Very good | Very good | Fair | Very good |
| Room-temperature strength | Medium–high | Medium–high | Medium–high | Medium–high |
| Forgeability | Good | Good | Excellent | Good |
| Main use | Hot rotating parts | Hot parts, pistons | Complex cool-running fittings | Pistons, impellers |
2A70 is often compared with the Russian AK4-1 alloy, which has a similar Fe-Ni-bearing chemistry. Substitution between these alloys requires design-authority approval.
How to order 2A70 forgings
- Drawing and standardForging or part drawing, alloy, temper (T6), and governing standard such as HB 5204, GJB 2351 or GB/T 3190 chemistry.
- InspectionUltrasonic class (e.g. GB/T 6519 or AMS-STD-2154), grain-flow or macro-etch checks, test-coupon location.
- QuotationWe confirm feasibility, tooling where needed, certification and delivery terms (EXW, FOB, CIF or DAP).
- DocumentsEN 10204 3.1 certificate with chemistry, mechanical results and heat-treat lot traceability.
- PackingCorrosion-protected forgings in wooden cases for export.
References and standards
- GB/T 3190 – Chemical composition of wrought aluminium and aluminium alloys
- HB 5204 – Aluminium alloy forgings for aviation (Chinese aviation industry standard)
- GJB 2351 – Specification for aluminium alloy forgings for aerospace (Chinese military standard)
- ASTM B247 – Aluminum and Aluminum-Alloy Die Forgings, Hand Forgings, and Rolled Ring Forgings (for Western comparison)
- ASM Handbook, Vol. 2 – Properties of Wrought Aluminum Alloys: 2618
2A70 aluminium (aluminum) forgings: FAQ
What is the equivalent of 2A70?
2618 / 2618A is the closest Western counterpart, with very similar Cu-Mg-Fe-Ni chemistry. The Russian AK4-1 alloy is also comparable.
Why is 2A70 used for impellers?
It keeps strength and fatigue resistance at the temperatures reached in compressors, and it forges well into thin-bladed shapes.
What is the strength of 2A70-T6 forgings?
Commonly quoted minimums are about 375 – 380 MPa tensile strength in all directions; typical values are around 440 MPa.
What temperature can 2A70 withstand?
It is generally used for long-term service up to about 250 °C, with strength decreasing progressively above 200 °C.
Can 2A70 be welded?
It is not intended for fusion welding; forgings are machined and joined mechanically.
Sourcing 2A70 forgings for hot-running parts?
Send the drawing, standard and quantity. We will confirm feasibility, inspection and a delivered price.
