Which aluminum alloys are suitable for making ships?

A common material for making ships is aluminum alloy. In the 1000-8000 series, some alloys are widely used in ships. Aluminum alloys are widely used in the shipbuilding industry because of their excellent properties such as light weight, corrosion resistance, and high strength.

The aluminum alloys used in the shipbuilding industry are usually divided into two series: 5000 series (Al-Mg) and 6000 series (Al-Mg-Si). These two series of aluminum alloys have very good moisture resistance and corrosion resistance, and can be used longer in humid environments.

What are the differences between the 500 series and the 6000 series in terms of shipbuilding?

5000 series alloys (aluminum-magnesium alloys)

Among the 5xxx series aluminum alloys, 5083 and 5086 are the two most widely used aluminum alloys.

Aluminum 5083 alloy

Composition: Contains magnesium (4.0-4.9%), manganese (0.4-1.0%) and trace chromium (0.05-0.25%).
Features:
High Strength: One of the strongest non-heat-treatable alloys.
Excellent Corrosion Resistance: Particularly resistant to seawater and industrial chemicals.
Good Weldability: Suitable for welding, a popular choice for ship hulls and superstructures.
Moderate Machinability: Can be machined to a satisfactory surface.

Aluminum 5086 Alloy

Composition: Contains magnesium (3.5-4.5%), manganese (0.2-0.7%), and iron (≤ 0.5%).
Features:
High Strength: Slightly lower in strength than 5083, but still very strong.
Excellent Corrosion Resistance: Particularly suitable for seawater and harsh environments.
Good Weldability: Commonly used for ship hulls and other structures in marine environments.
Good Formability: Can be easily formed into complex shapes.

6000 Series Alloys (Aluminum-Magnesium-Silicon)

Aluminum 6061 Alloy

Composition: Contains magnesium (0.8-1.2%), silicon (0.4-0.8%), and small amounts of copper (0.15-0.4%) and chromium (0.04-0.35%).
Features:
Medium-high strength: Good strength after heat treatment.
Good corrosion resistance: Suitable for marine environments.
Excellent weldability: Can be welded by all methods.
Good machinability: Commonly used in marine fittings, small boats and masts.
Good formability: Can be easily formed into various shapes.

Aluminum 6082 Alloy

Composition: Contains magnesium (0.6-1.2%), silicon (0.7-1.3%) and manganese (0.4-1.0%).
Features:
High strength: Higher strength than 6061, suitable for more demanding applications.
Good corrosion resistance: Ideal for marine and structural applications.
Good weldability: Suitable for welding and can be heat treated.
Good machinability: Commonly used in shipbuilding structural applications and decks.

Comparison and Applications of 5-Series and 6-Series Aluminum Alloys

5000 Series vs. 6000 Series

Item	5000 series	6000 series
Strength	5000 Series alloys generally have higher strength in the non-heat-treatable condition compared to 6000 Series.
Corrosion Resistance	Both series have excellent corrosion resistance, but 5000 Series generally outperforms in marine environments due to the higher magnesium content.
Weldability	Both series are highly weldable, but 5000 Series alloys may be better suited for large structural components due to their better performance and the absence of post-weld heat treatment.
Machinability	6000 Series alloys generally have better machinability, making them suitable for fine fittings and components.

Applications in Shipbuilding

5083 and 5086: Widely used in hulls, superstructures, and other large structural components due to their strength and corrosion resistance.
6061 and 6082: Used in various parts of ships, such as fittings, masts, ladders, and frames. They are easy to machine and have good overall properties, making them suitable for smaller parts and structural elements.

The 5000 series alloys, especially 5083 and 5086, are favored for their high strength and corrosion resistance, making them ideal for hulls and large structural parts. The 6000 series alloys, including 6061 and 6082, are favored for their excellent machinability, weldability, and suitability for smaller parts and fittings.