Fusion welding
TIG and other arc processes are used with matched Al-Mg-Li or Al-Mg fillers. Thorough cleaning and removal of the surface layer are essential to avoid porosity from lithium-rich oxide and hydrogen.
Aluminium-lithium alloy guide
Russian 1420 (01420) Aluminium-Lithium Alloy
1420, also written 01420, is a Russian aluminium-magnesium-lithium alloy with about 5–6 % magnesium and 2 % lithium. It is roughly 10 % lighter and noticeably stiffer than conventional aluminium alloys, and, unusually for an Al-Li alloy, it can be fusion welded. It was developed for welded aircraft structures and is supplied mainly as sheet, plate and extrusions against aerospace specifications.
- System
- Al-Mg-Li (+ Zr)
- Density
- About 2.47 g/cm³
- Key feature
- Fusion weldable Al-Li alloy
- Forms
- Sheet, plate, extrusions
What makes 1420 different
Lithium is the lightest metal. Each 1 % of lithium added to aluminium lowers density by about 3 % and raises the elastic modulus by about 6 %. Combined with magnesium, which is also lighter than aluminium, this gives 1420 a density near 2.47 g/cm³, compared with 2.64 g/cm³ for an Al-6 % Mg alloy such as АМг6 and 2.78 g/cm³ for 2024.
1420 was developed in the Soviet Union in the 1960s under the metallurgist I. N. Fridlyander and became the first aluminium-lithium alloy used in welded primary structure. Its magnesium content makes it behave in welding much like a 5xxx alloy, so welded fuselage sections and fuel tanks could be built without rivets, saving further weight.
The trade-offs are moderate strength and fracture toughness by modern standards, sensitivity to processing, and the need for specialised melting because lithium is reactive. Later Russian alloys such as the scandium-modified 1421 and the Al-Cu-Li family addressed some of these limits, but 1420 remains the reference Al-Mg-Li grade.
1420 nominal composition
Published composition limits vary slightly between Russian aerospace documents. The table gives the commonly cited ranges; the governing specification and certificate control acceptance.
| Element | Typical range (%) | Role |
|---|---|---|
| Magnesium (Mg) | about 5.0 – 6.0 | Solid-solution strengthening; lowers density |
| Lithium (Li) | about 1.9 – 2.3 | Lowers density, raises modulus, forms strengthening Al₃Li (δ′) |
| Zirconium (Zr) | about 0.09 – 0.15 | Controls recrystallisation and grain size |
| Iron (Fe) | ≤ about 0.2 | Impurity |
| Silicon (Si) | ≤ about 0.15 | Impurity |
| Sodium (Na), hydrogen | Very low | Strictly limited; harmful to ductility and weld quality |
| Aluminium (Al) | Remainder |
Properties compared with conventional alloys
| Property | 1420 (aged sheet, indicative) | АМг6 / 5083 class | 2024-T3 |
|---|---|---|---|
| Density (g/cm³) | ≈ 2.47 | ≈ 2.64 | 2.78 |
| Elastic modulus (GPa) | ≈ 75 | ≈ 71 | ≈ 73 |
| Tensile strength | ≈ 400 – 450 MPa | ≈ 320 – 340 MPa | ≈ 480 MPa typical |
| Yield strength | ≈ 260 – 300 MPa | ≈ 160 MPa | ≈ 345 MPa typical |
| Elongation | ≈ 8 – 10 % | ≈ 15 – 20 % | ≈ 18 % |
| Fusion weldability | Yes | Yes | No |
1420 values are indicative ranges from published literature for aged sheet; they vary with product form and heat treatment. Design to the guaranteed values in the order specification.
The real advantage shows in specific properties. Dividing modulus by density, 1420 is roughly 13–16 % stiffer per kilogram than 5083 or 2024, which matters for buckling-critical panels and stiffness-driven structures.
Product forms and heat treatment
Typical supply
- Sheet
- Thin and medium sheet for skins and welded panels
- Plate
- For machined frames and fittings
- Extrusions
- Stringers and profiles
- Heat treatment
- Solution treatment, quench and artificial ageing; condition stated in the order
- Testing
- Tensile by direction, weld qualification, corrosion and ultrasonic tests per specification
Al-Li alloys need care in handling scrap: lithium-bearing swarf and offcuts must be segregated from ordinary aluminium scrap, because lithium contaminates other alloys and the chips are reactive.
Welding and fabrication
Weld properties
Weld zones lose some strength relative to aged parent metal, as with any precipitation-hardened alloy; design allowables come from qualified procedures.
Forming
Form in the quenched or annealed condition, then age. Formability is lower than for 5xxx alloys.
Machining
Machines like other medium-strength aluminium alloys; collect and store swarf separately and dry.
Where 1420 is used
- Welded fuselage sections and cockpit structures of military aircraft
- Welded integral fuel tanks
- Lightweight panels, window and door frames in aircraft
- Rocket and missile structures where welded light construction pays
- Specialist lightweight structures outside aerospace, subject to cost
Western equivalents in purpose rather than chemistry are Al-Li alloys such as 8090 and 2090, and for welded tanks, 2195 and 2219; none is a direct drop-in replacement.
References and standards
- Fridlyander I. N. et al. – Aluminium-lithium alloys: development and use in Russian aircraft (VIAM publications)
- ASM Handbook, Vol. 2 – Properties and Selection: Nonferrous Alloys, aluminium-lithium alloys
- GOST 4784 – Aluminium and wrought aluminium alloys. Grades
- Total Materia – Aluminium-lithium alloys overview
1420 aluminium-lithium alloy: frequently asked questions
Is 1420 a normal Al-Mg alloy?
No. It contains about 2 % lithium as well as 5–6 % magnesium, which lowers density to about 2.47 g/cm³ and raises stiffness compared with ordinary Al-Mg alloys.
Can 1420 be welded?
Yes. It is one of the few aluminium-lithium alloys designed for fusion welding, and was used for welded aircraft fuselage sections and fuel tanks.
What is the Western equivalent of 1420?
There is no direct equivalent. 8090 is the closest in purpose among Al-Li alloys; substitution needs engineering approval.
How much lighter is 1420 than 2024?
About 11 % by density (2.47 vs 2.78 g/cm³), with a slightly higher elastic modulus.
What does the 0 in 01420 mean?
It is an older way of writing the same Russian grade number; 1420 and 01420 refer to the same alloy.
Can Metline supply 1420?
We review 1420 enquiries case by case against the specification, form and documentation required, and can propose approved alternatives.
Working with aluminium-lithium alloys?
Send the specification, product form, size and quantity. We will reply on availability, documents and alternatives.
