Aluminum 5086 - EN AW-5086 - EN AW-AlMg4 - 3.3545 - AB 5086

How did 5086 aluminium emerge and position itself?

The 5086 aluminium alloy (EN AW-5086, UNS A95086, AlMg4/3.3545) appeared in the mid-20^th century and received its standard designation in 1954, within the Al-Mg “5xxx” family, designed for weldability and corrosion resistance. Today, it is well established in product standards (e.g. EN 573, EN 485, ASTM B209, ASTM B928). Its industrial adoption follows the “marine corrosion resistance + welding” combination it delivers.

Adoption and competition

In the 1960s, the US Navy adopted it in sheet (H32) and extrusions (H111). The H116/H117 tempers, introduced later, help limit harmful intergranular precipitation and exfoliation risks, with corrosion requirements verified through dedicated tests.

Thanks to very reliable weldability and better mechanical performance, 5086 (Rm (UTS): < 335 MPa in H35 and > 275 MPa) often replaces 5052 (Rm (UTS): < 265 MPa in H35 and > 215 MPa) in highly loaded hulls and structures. The latter still keeps an advantage when very tight bends are required, and for less highly stressed parts.

Chemical composition and the role of alloying elements

The alloy is non-heat-treatable; the main alloying element is magnesium (≈ 4% on average). It provides solid-solution strengthening and excellent weldability. Manganese (≈ 0.45%) and chromium (0.15%) control grain size and limit brittle phases, improving strength and resistance to intergranular corrosion. Typical impurities (Si, Fe, Cu, Zn and Ti) are controlled, and the remainder is aluminium.

How do the mechanical properties of 5086 vary with temper?

5086 strengthens through work hardening (no precipitation hardening). In O (annealed), a typical 0.2% proof strength Rp0.2 ≈ 110 MPa, ultimate tensile strength Rm ≈ 270 MPa, and elongation at fracture A ≈ 20% are observed. These values naturally vary with thickness and specifications.

Comparison of a few tempers (H32, H116, annealed)

Work hardening increases strength, but reduces elongation and fatigue strength. Thus, in H32, Rp0.2 ≈ 210 MPa and Rm ≈ 300 MPa (typ.) are commonly seen. The H116 temper, controlled for marine service, shows the same characteristics as H32. Brinell hardness increases from about 65 HB (O) to 100 HB (H18) in harder tempers (typ.).

Comparative table of mechanical properties (sheet, typ.)

How does 5086 resist corrosion?

5086 belongs to the corrosion-resistant alloys: the protective oxide film and the lack of copper ensure excellent performance in seawater. Long-term marine exposures report low mechanical losses after 10 years. It is considered “marine grade” alongside 5052 and 5083.

Sensitivities to different corrosion modes and dedicated tempers

After prolonged exposure at ≈ 60–100 °C (≈ 140–212 °F), β precipitates (Al₃Mg₂) can form along grain boundaries, promoting intergranular corrosion, exfoliation, and stress corrosion cracking. Good practice limits service temperature to ≈ 65 °C (≈ 149 °F) in corrosive environments. Tempers such as H116/H321 require testing, for example:

• No degradation above the “PB” level (pitting and slight blistering).
• After immersion in concentrated nitric acid, must not lose more than a specified mass per unit area.

Comparison among the 5000-series alloys

5086, with slightly less magnesium than 5083, is generally a bit less sensitive to corrosion. 5456 (≈ 5% Mg) can offer higher strength, but has historically been more prone to stress corrosion cracking; hence the frequent use of 5086/5083 in today’s welded marine structures.

How to process and use 5086 alloy?

Its cold working is excellent in O/H111: bending, rolling, moderate deep drawing, and forming are performed easily. In H36/H38, ductility decreases and requires larger bend radii. Hot forming (≈ 200–250 °C / ≈ 392–482 °F), extrusion, and forging remain possible, but are rarely needed.

Weldability & machining

5086 welds very well (TIG, MIG) with common filler wires (5356, 5183). The fusion zone tends back toward an “annealed” condition in the weld bead. No post-weld heat treatment is required; light stress relieving and designs that avoid stress concentrations remain recommended. FSW has shown good experimental results.

Machinability is moderate: the metal is soft in O/H111, with a tendency to gall and produce long chips. Once work-hardened, chip break-up improves and machining quality increases.

Which applications best illustrate its use?

Marine and offshore

Main domain: hulls, decks, superstructures, floating docks, exposed structures, often in H116/H321. Shipyards use thicknesses up to 30 mm (≈ 1.18 in), with excellent performance after welding and in saltwater.

Aerospace and space

Targeted uses where weldability and cryogenic performance matter: cryogenic tanks/enclosures, missile/rocket components, lightly loaded non-pressurized equipment. No major structural use in modern airframes.

TL;DR

A “marine grade” Al-Mg alloy, 5086 combines excellent corrosion resistance (seawater), very good weldability, and solid mechanical strength in H3x/H116 tempers. It does not strengthen with heat, gains strength at cryogenic temperatures, and should avoid prolonged exposure at ≈ 60–100 °C (≈ 140–212 °F). A staple of marine/offshore construction, it is also used in cryogenic service and in non-structural aerospace/space equipment. Compared with 5083, it is slightly less strong but often slightly less prone to sensitization; it outperforms 5052 for highly loaded hulls, while 6061-T6 is preferred for extrusions and machining away from seawater exposure.