5083-O Aluminum Alloy: Marine & Cryogenic Structural Plate

ASTM B209 / ASTM B928 · Published: 2026-06-01 · Updated: 2026-06-02

5083 is the highest-strength non-heat-treatable aluminum alloy in commercial use, containing 4.0-4.9% magnesium, 0.4-1.0% manganese, and 0.05-0.25% chromium. The high magnesium content provides exceptional solid-solution strengthening; manganese and chromium control grain structure and improve stress corrosion cracking resistance. Unlike 5xxx-series alloys with <3% Mg (5052, 5454) which can be used at temperatures up to 150°C, 5083 with >4% Mg is susceptible to sensitization — continuous exposure to temperatures above 65°C causes Mg2Al3 (beta phase) precipitation at grain boundaries, leading to intergranular corrosion and stress corrosion cracking in seawater.

5083 is the standard hull plate material for high-speed aluminum ferries, military patrol boats, LNG (liquefied natural gas) carrier spherical tanks, and cryogenic storage vessels. The alloy retains excellent toughness at cryogenic temperatures — Charpy V-notch impact values actually increase at -196°C compared to room temperature, making 5083 approved for LNG containment systems operating at -162°C. O-temper (annealed) is used for applications requiring maximum formability; H321 (strain-hardened and stabilized) provides approximately 60% higher yield strength with good formability and is the standard temper for hull plate. Welding with 5183 or 5356 filler rod — 5183 provides higher weld strength (matching 5083 base metal strength).

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