5A90 (1420) Aluminum Lithium Alloy: Properties and Applications
In the evolution of aerospace materials, weight reduction has always been one of the most critical design objectives. To achieve lighter structures without sacrificing strength, stiffness, or durability, aluminum alloys have been continuously optimized.
Among these developments, aluminum–lithium (Al-Li) alloys stand out as one of the most important breakthroughs.
Within this material family, 5A90 (also known as 1420 aluminum alloy) represents a well-established Al–Mg–Li alloy system developed and widely studied in China, offering exceptional weight savings and structural efficiency for aerospace applications.
What is al–li alloy?
An aluminum–lithium alloy (Al-Li alloy) is a high-performance aluminum alloy in which a small amount of lithium (typically 1–3%) is added to the aluminum matrix, often together with elements such as magnesium, copper, zirconium, or silver.
Unlike conventional aluminum alloys that focus primarily on strength, Al-Li alloys are designed to optimize:
Density reduction
Specific strength
Specific stiffness
Fatigue performance
Because of these advantages, aluminum–lithium alloys are primarily used in aerospace and spaceflight structures, where weight efficiency is critical.
What does lithium do to aluminum?
Lithium plays a unique role in aluminum alloys and fundamentally changes their mechanical behavior:
1. Density reduction
Lithium is the lightest metallic element.
For aluminum alloys, each 1% increase in lithium content reduces density by approximately 3%.
2. Increased elastic modulus
At the same time, each 1% lithium increases the elastic modulus by about 6%, improving stiffness without adding weight.
3. Precipitation strengthening
Lithium forms fine δ′ (Al₃Li) precipitates, which strengthen the alloy while maintaining low density.
4. Improved structural efficiency
Higher stiffness and lower weight allow thinner sections and lighter structural designs—ideal for aircraft and spacecraft components.
This rare combination of lower density and higher stiffness is what makes lithium such a powerful alloying element in aluminum.
What is 1420 aluminum material?
1420 aluminum alloy originated from the former Soviet aluminum–lithium alloy system and is a classic Al–Mg–Li alloy known for its exceptionally low density.
In the Chinese alloy designation system, its equivalent and industrialized grade is 5A90 aluminum–lithium alloy.
Key Characteristics of 5A90 (1420):
Very low density: approximately 2.47 g/cm³
High specific strength and stiffness
Excellent corrosion resistance (typical of Al–Mg–Li systems)
Good weldability and manufacturability
Unlike high-copper Al-Li alloys, 5A90 emphasizes lightweight efficiency and balanced performance rather than maximum absolute strength.
What Is aluminum–lithium used for?
Aluminum–lithium alloys are not general-purpose materials. They are engineered specifically for high-value, weight-critical structures, including:
Aerospace Applications
Aircraft fuselage skins
Wing panels and wing structures
Stringers, frames, and stiffeners
Space Applications
Cryogenic fuel tanks
Lightweight pressure vessels and load-bearing shells
Their primary benefit can be summarized as:
Maximum weight reduction while meeting strength, fatigue, and durability requirements.
What is the number for lithium aluminum alloy
There is no single global numbering system for aluminum–lithium alloys. Designations depend on national standards and alloy development routes:
AA (United States):
2090, 2099, 2050, 2195, 2198
Russian system:
1420, 1421, 1440
Chinese system:
5A90 (corresponding to 1420)
Therefore, 5A90 is the Chinese designation, while 1420 is the commonly referenced international (Russian-system) name for the same alloy family.
However, different numbers often represent different alloy systems and performance priorities, which is why understanding the alloy chemistry is more important than the designation itself.
5A90 vs 2198 vs 2050: Al–Li alloy comparison
Alloy systems and design focus
| Alloy | Alloy System | Design Focus |
|---|---|---|
| 5A90 (1420) | Al–Mg–Li | Extreme weight reduction, corrosion resistance |
| 2198 | Al–Cu–Li (3rd generation) | High strength, improved weldability |
| 2050 | Al–Cu–Li (3rd generation) | Thick plate performance, damage tolerance |
Density and structural efficiency
| Property | 5A90 | 2198 | 2050 |
|---|---|---|---|
| Density (g/cm³) | ~2.47 | ~2.60 | ~2.65 |
| Strength level | Medium | High | High |
| Specific strength & stiffness | Very high | High | High |
| Corrosion resistance | Very good | Good | Good |
Key takeaway:
5A90 offers the lowest density and highest weight-saving potential, while 2198 and 2050 focus more on high-load structural performance.
Manufacturing and application differences
| Aspect | 5A90 | 2198 | 2050 |
|---|---|---|---|
| Weldability | Good | Excellent | Good |
| Anisotropy control | Moderate | Excellent | Excellent |
| Thick plate capability | Moderate | Good | Excellent |
| Typical product forms | Sheet, extrusions | Sheet | Thick plate, extrusions |
Typical aerospace applications
| Alloy | Typical Uses |
|---|---|
| 5A90 (1420) | Fuselage skins, wing structures, stringers |
| 2198 | Welded fuselage panels, aircraft skins |
| 2050 | Frames, bulkheads, thick structural parts |
These alloys are complementary rather than competitive in modern aircraft design.
Why 5A90 (1420) aluminum–lithium alloy matters
The engineering value of 5A90 lies in its ability to:
Deliver maximum weight reduction for large aerospace structures
Improve stiffness without increasing mass
Provide good corrosion resistance for long service life
Maintain reasonable manufacturability and weldability
It is often considered a lightweight alternative to conventional high-strength aluminum alloys when structural efficiency is the primary goal.
Aluminum lithium alloy for sale
At Shenzhen Chinalco Metal, we offer aluminum lithium alloy for sale, including 5A90 (1420). We supply it in different forms and sizes.
| Product Type | Size Specifications |
|---|---|
| Round/Square Ingots | 800×600×200 mm, 300×700×950 mm, and other customizable sizes |
| Rolled Plates | 60×5 mm, 80×7 mm, 105×4 mm, 220×26 mm, 250×40 mm, and other customizable sizes |
| Rolled Bars | Φ9.5 mm, Φ12 mm, Φ22 mm, Φ30 mm, Φ60 mm, Φ100 mm, and other customizable sizes |
| Forged Plates | 100×600×1500 mm, 120×600×1200 mm, 150×600×1000 mm, and other customizable sizes |
| Forged Bars | Φ30 mm – Φ400 mm |
| Sheet Material | Thickness: 1.0–50 mm; Max width × length: 1200 mm × 4000 mm |