For decades 5083-H131 has been the standard weldable aluminium armour, but newer plates now give more ballistic and blast protection per kilogram. This guide compares the main options (higher-magnesium 5xxx such as 5059, scandium- and zirconium-modified 5xxx, 7039, 2139 and 7085) and explains how to choose between them using the military specifications, threat levels and fabrication needs of a real vehicle.
Aluminium armour protects a vehicle by mass efficiency. An aluminium plate is about three times thicker than a steel plate of the same weight, so it is far stiffer in bending, needs fewer stiffeners and can form a self-supporting hull. That is why the hulls of many tracked and wheeled armoured vehicles, from personnel carriers to amphibious craft, are welded aluminium.
The baseline is 5083 in the strain-hardened H131 temper, specified in the US under MIL-DTL-46027. It welds well, resists corrosion and absorbs blast by deforming without cracking. Its weakness is moderate strength, which limits resistance to armour-piercing rounds. The 7xxx alloy 7039 stops projectiles better but is prone to stress-corrosion cracking and harder to weld.
New armour plates try to close that gap: more strength and ballistic resistance than 5083, while keeping as much weldability, toughness and corrosion resistance as possible. Three routes dominate: raising the magnesium content of 5xxx alloys (5059), adding scandium and zirconium to refine grain structure in 5xxx plate, and using high-strength 2xxx or 7xxx alloys (2139, 7085) where welding is limited or not needed.
The table compares the main wrought aluminium armour alloys qualitatively. Exact properties depend on thickness, temper and specification revision, so design values must come from the governing specification and the mill certificate.
| Alloy / temper | Family | Typical specification | Weldability | Corrosion resistance | Ballistic resistance vs 5083 | Typical role |
|---|---|---|---|---|---|---|
| 5083-H131 | Al-Mg (non-heat-treatable) | MIL-DTL-46027 | Excellent | Excellent | Baseline | Welded hulls, floors, structure |
| 5456-H116 / H131 | Al-Mg | MIL-DTL-46027 | Excellent | Very good | Slightly higher | Hulls and decks |
| 5059-H131 / H136 | High-Mg Al-Mg with Zn, Zr | MIL-DTL-46027 (later revisions) | Very good | Very good | Higher | Lighter welded hulls, blast floors |
| Sc/Zr-modified 5xxx | Al-Mg with Sc and Zr | Development and national specifications | Very good | Good to very good | Higher (alloy-specific) | Candidate replacement for 5083 and 5059 |
| 7039-T64 | Al-Zn-Mg | MIL-DTL-46063 | Limited | Fair (stress-corrosion sensitive) | Much higher | Turret and glacis plates |
| 2139-T8 | Al-Cu-Mg-Ag | MIL-DTL-32341 | Weldable in specified thicknesses | Fair to good | Much higher | High-threat structure and appliqué |
| 7085, 7056, 7075 (appliqué) | Al-Zn-Mg-Cu | MIL-DTL-32375 | Not for welding | Requires protection | Highest of the aluminium grades | Bolt-on appliqué panels |
MIL-DTL-46027 covers weldable 5083, 5456 and 5059 plate; MIL-DTL-32341 states that weldability has been established only for 2139 in certain thicknesses, with its other alloys limited to appliqué use; MIL-DTL-32375 covers unweldable appliqué plate. Always check the current revision.
5059 contains more magnesium than 5083, plus zinc and zirconium. Zirconium forms fine Al3Zr dispersoids that pin grain boundaries, and the higher magnesium raises strain-hardening response. The result is markedly higher strength in H131 and H136 tempers, and a US Army Research Laboratory programme evaluated 5059-H131 and H136 as a direct alternative to 5083-H131 in ballistic tests.
Because it is still a non-heat-treatable 5xxx alloy, 5059 welds with the same processes and similar filler metals as 5083 (5183 or 5556 type), and the heat-affected zone does not lose strength through over-ageing as it does in 7xxx alloys. Its main limits are higher cost and a narrower supply base. Like all alloys above about 3 % magnesium, it must be kept out of sustained service above roughly 65 °C, where long exposure can sensitise grain boundaries to intergranular corrosion.
Adding a few tenths of a percent of scandium together with zirconium produces Al3(Sc,Zr) particles that are extremely effective at stopping recrystallisation and refining grain size. In Al-Mg alloys this raises yield strength substantially without losing the corrosion resistance and weldability of the 5xxx family. Patent literature for Al-Mg armour plate also allows small scandium and zirconium additions and reports V50 ballistic gains over a 5083-H131 baseline when tested to MIL-DTL-46027 procedures.
Under ballistic and blast loading these fine-grained plates show strong strain-rate hardening: the faster they are loaded, the stronger they behave, and deformation spreads across many narrow shear bands rather than concentrating in one. That combination of higher dynamic strength and preserved ductility is why developers claim protection approaching 7039 with blast behaviour closer to 5xxx.
Treat these claims carefully. Sc-modified armour plates are often proprietary, specified under national or company standards rather than a published military specification, and their ballistic data depend on the projectile, test range and acceptance criteria used. Before adopting one, ask for third-party test reports against your threat, weld procedure qualification and corrosion test results (for example ASTM G66 and G67 for 5xxx alloys).
The traditional high-strength aluminium armour. Far better against armour-piercing rounds than 5083, but sensitive to stress-corrosion cracking and exfoliation, and weld zones lose strength. Used for turret and glacis plates with careful design and coatings.
An Al-Cu-Mg-Ag alloy developed for armour, with high strength, good toughness and better stress-corrosion behaviour than 7039. Weldable in the thicknesses established by MIL-DTL-32341.
Thick-section aerospace 7xxx alloys used as unweldable appliqué armour to MIL-DTL-32375. Bolted onto a welded 5xxx hull to defeat higher threats.
Lower density and higher stiffness. Covered alongside 2139 in MIL-DTL-32341 for appliqué use; mainly of interest where weight savings justify cost.
A common modern architecture combines both groups: a welded hull in 5083, 5059 or a Sc-modified 5xxx for structure, blast and corrosion resistance, plus bolt-on 7xxx, 2139 or ceramic appliqué panels that are sized to the mission threat and can be replaced after damage. See our page on multi-ply composite armour plate.
NATO STANAG 4569 and its test procedure AEP-55 define protection levels for logistic and light armoured vehicles. Kinetic energy levels rise from ball rounds at level 1 to 7.62 mm armour-piercing rounds at level 3 and 14.5 mm AP at level 4. Mine-blast levels (2a, 2b, 3a, 3b, 4a, 4b) are defined by charge mass and whether it detonates under a wheel or the hull centre.
| What drives thickness | Effect | Practical note |
|---|---|---|
| Threat calibre and type | AP cores need far more aluminium than ball rounds | Higher threats are usually met with appliqué rather than thicker hull plate |
| Angle of impact | Sloped plate presents a longer path and can deflect rounds | Thickness tables always quote the obliquity used in testing |
| Alloy and temper | Stronger alloys need less thickness for the same V50 | Compare only at the same threat, range and angle |
| Blast charge | Floor and belly plates must deform without rupture | Ductility and weld quality matter as much as strength |
Ballistic limit figures (V50, the velocity at which half the rounds penetrate) are only comparable when the projectile, obliquity and test standard match. Treat any single thickness-versus-threat chart as a guide to be confirmed by tests on the actual plate lot and weld procedure.
Metline supplies aluminium armour plate in 5083, 5456 and 5059 and in high-strength grades on request, to the specification on your drawing, with cutting and machining of blanks and parts to drawing. Each delivery carries an EN 10204 3.1 mill certificate; 3.2 certification with third-party inspection, ultrasonic reports and ballistic test documentation can be arranged where the programme requires them.
There is no single best grade. 5083-H131 and 5059 suit welded hulls that need blast and corrosion resistance; 7039, 2139 and 7085 give higher ballistic resistance but with welding and corrosion limits. Most vehicles combine a welded 5xxx hull with bolt-on high-strength appliqué.
5059 is stronger than 5083 in comparable H131 tempers and gives better ballistic protection at the same thickness, while keeping similar weldability and corrosion resistance. It costs more and is made by fewer mills.
Scandium with zirconium forms very fine particles that refine grain size and stop recrystallisation, raising strength and strain-rate hardening in Al-Mg plate without losing weldability. Such plates are often proprietary, so ask for independent ballistic, weld and corrosion test reports.
It can be welded, but the weld zone loses strength and the alloy is sensitive to stress-corrosion cracking, so welding is restricted and carefully controlled. Many designs use 7xxx plate as bolted appliqué instead.
In the US, MIL-DTL-46027 covers weldable 5083, 5456 and 5059 armor plate. MIL-DTL-32341 covers 2139 and related alloys, MIL-DTL-46063 covers 7039, and MIL-DTL-32375 covers unweldable appliqué plate.
Yes. Plate can be supplied cut to size or as parts cut and machined to your drawing, with mill certificates and agreed inspection.
Every lot comes with an EN 10204 3.1 mill certificate showing chemistry and mechanical properties. Ultrasonic reports, corrosion tests, ballistic acceptance results and 3.2 third-party certification can be arranged when the order calls for them.
Tell us the threat level or alloy, specification, thicknesses and quantities. We will propose suitable plate and documentation.
