The 5083 Grade and the H111 Temper
5083 is an aluminium-magnesium alloy belonging to the 5xxx series. Because the alloying additions are held in solid solution rather than in a precipitate, it cannot be strengthened by heat treatment; strength is developed by strain hardening, and the H111 designation means the material has been strain hardened and then given a stabilising thermal treatment that leaves it slightly softer than a fully hardened temper while improving ductility and dimensional stability.
That combination makes 5083-H111 the default choice for welded structures that must survive low temperatures, salt water and impact. It retains useful toughness down to cryogenic temperatures and is one of the few widely available aluminium alloys approved for liquefied gas service. At 5 mm nominal thickness the material sits in the sheet-to-plate transition range, which is convenient for both formed and fabricated work.
Chemical Composition and Mechanical Properties
Composition and mechanical limits are specified in ASTM B209, with equivalent European requirements in the EN 573-3 composition standard and the EN 485-2 mechanical property standard. The table below gives the principal figures a buyer can rely on when writing a specification.
| Element or property | Value | Source basis |
|---|---|---|
| Magnesium | 4.0 to 4.9% | ASTM B209 composition |
| Manganese | 0.40 to 1.00% | ASTM B209 composition |
| Chromium | 0.05 to 0.25% | ASTM B209 composition |
| Silicon, iron, copper, zinc, titanium | Silicon 0.40 max, iron 0.40 max, copper 0.10 max, zinc 0.25 max, titanium 0.15 max | ASTM B209 composition |
| Tensile strength, H111 | 275 to 350 MPa | EN 485-2 for this temper |
| 0.2% proof strength, H111 | 125 MPa minimum | EN 485-2 for this temper |
| Density | 2.66 g/cm3 | Typical physical data |
| Modulus of elasticity | About 71 GPa | Typical physical data |
The relatively low proof strength compared with a heat-treatable alloy is accepted deliberately: 5083 deforms before it fractures, and the weld zone retains a high proportion of parent metal properties, which is the whole reason the grade is specified for fabricated assemblies. Sustained service above about 65 degrees Celsius is not recommended, because prolonged exposure at higher temperature can sensitise the magnesium-rich grain boundaries and increase susceptibility to stress corrosion cracking.
5 mm Thickness, Tolerances and Flatness
At 5 mm the product is ordered with a specified thickness tolerance, width and length, and a flatness requirement. Thickness tolerance and edge condition should be stated explicitly in the purchase order rather than left to mill default practice, because the acceptable band widens as gauge increases and a part designed to nominal thickness may not tolerate the full permitted range.
Flatness matters where the plate will be welded into a panel assembly or machined on a vacuum table. Plates supplied in cut lengths should be handled on a flat surface and stored horizontally with uniform support; aluminium plates held on edge for long periods tend to take a permanent set.
Double-Sided Lamination: Process and Purpose
Laminated supply means a protective film is applied to both faces, normally a 50 to 100 micrometre polymer film with a low-tack adhesive. The purpose is to prevent mechanical scratching and handling marks between the mill and the fabricator, which matters most for material that will be anodised, powder coated or left with a visible mill finish. Because film applied to one face only leaves the reverse exposed, double-sided protection is preferred for plates that are handled on both sides during cutting and forming.
The film must be removed within the supplier's recommended storage period, typically within a few months of application and before any heat exposure, since adhesive residue can bake onto the surface. Wherever possible, film should be trimmed back from a weld joint, because the adhesive and polymer will contaminate the weld pool and produce porosity.
Fabrication Notes for 5083-H111
Filler selection for gas tungsten arc or gas metal arc welding normally uses a 5183 or 5356 filler, both of which are compatible with the magnesium content of the base alloy. Cold forming is possible at 5 mm, but bending should be done with a generous radius and, where the bend is severe, the material is better ordered in the softer O temper and allowed to work harden in service.
Machining is straightforward at this thickness, though the alloy is gummy and benefits from sharp tooling and generous chip clearance. 5083 is not intended for elevated-temperature service and should not be substituted where a heat-treatable grade is required for strength at temperature.
Frequently Asked Questions
Q: What does the H111 temper mean for 5083?
A: The material has been strain hardened and then given a stabilising treatment, so it is slightly softer than a fully hardened temper but has better ductility and stable properties in service.
Q: Can 5083 be strengthened by heat treatment?
A: No. The magnesium is held largely in solid solution, so the alloy is non-heat-treatable and gains strength only through strain hardening.
Q: How much magnesium does 5083 contain?
A: Between 4.0 and 4.9% according to the ASTM B209 composition limits, balanced by 0.40 to 1.00% manganese and 0.05 to 0.25% chromium.
Q: Why is 5083-H111 not recommended for hot service?
A: Prolonged exposure above about 65 degrees Celsius can sensitise the magnesium-rich grain boundaries and increase the risk of stress corrosion cracking.
Q: Which filler metal is used for welding 5083?
A: A 5183 or 5356 filler is normally specified, since both match the magnesium content of the base alloy and retain good weld properties.
Q: Why is protective film applied to both faces?
A: To prevent handling scratches and marks on material that will be left with a visible or anodised finish, and because plates are normally handled on both sides during cutting and forming.
