Aluminum alloys

Next to steel, aluminum is the most commonly used and commercially available metal. Its light weight and high strength-to-weight ratio make it a good choice for just about anything you can make out of metal. Its alloys generally that have excellent corrosion resistance, good workability (machinability) and good to excellent weldability, are often used in marine applications (marine grade aluminum).

The Aluminum Association, Inc. uses a standard four-digit numerical system to indicate the main alloying additives, as shown below:

• 1xxx - Pure aluminum at least 99.0%, no alloying elements
• 2xxx - Main alloying element copper (Cu)
• 3xxx - Main alloying element manganese (Mn)
• 4xxx - Main alloying element silicon (Si)
• 5xxx - Main alloying element magnesium (Mg) (marine grade alloys)
• 6xxx - Main alloying elements magnesium (Mg) and silicon (Si) (marine grade alloys)
• 7xxx - Main alloying element zinc (Zn)
• 8xxx - Other elements
• 9xxx - Not used

In addition, a temper designation is used to show the cold-working and heat-treating histories:

• F - fabricated
• H - strain hardened
• O - annealed (brought to desired consistency, texture or hardness by a process
        of gradual heating and cooling)
• W - solution heat-treated
• T - Heat treated to produce stable tempers other than F, O, H or W

The following table gives main features of some marine grade aluminum alloys (series 5xxx and 6xxx; in blue font) and a few others for reference:

Aluminum Grade-Temper	General	Yield strength (psi)	Ultimate Tensile Strength (psi)	Workability	Weldability	Hardness (Brinell)	Chemistry
Pure Al 1xxx Series	Low strength (soft), non-magnetic, highly electrically and thermally conductive, high corrosion resistance. Used for wrought aluminum elements.	24,000	29,700			12-55	Al 99.0% min
2011-T3	Most workable of all aluminum alloys, excellent surface finish	43,000	55,000	Excellent	Average	95	Al 91.2-94.6% Bi 0.2-0.6% Cu 5.0-6.0% Fe 0.7% max Mg 2.1-2.9% Pb 0.2-0.6% Si 0.4% max
2024-T3	Very strong compared to most aluminum alloys. High percentage of copper makes it susceptible to corrosion. High fatigue resistance. Used mainly in aerospace applications.	50,000	70,000	Average	Non-weldable	120	Al 95.7-97.7% Cr 0.1% max Cu 3.8-4.9% Fe 0.5% max Mg 1.2-1.8% Mn 0.3-0.9% Si 0.5% max
5052-H32	Marine grade. Most suited for forming operations, very good corrosion resistance.	28,000	33,000 12% elong.	Fair	Good	60	Al 95.7-97.7% Cr 0.15-0.35% Cu 0.1% max Fe 0.4% max Mg 2.2-2.8% Mn 0.1% max Si 0.25% max
5083-H321	Marine grade. The highest strength non-heat-treatable aluminum alloy in commercial use. It retains excellent tensile strength in the weld zone. Excellent corrosion resistance. (Platypus is built in this alloy)	33,000	46,000 16% elong.	Good	Excellent	85	Al 92.4-95.6% Cr 0.05-0.25% Cu 0.1% max Fe 0.4% max Mg 4.0-4.9% Mn 0.3-1.0% Si 0.4% max Ti 0.15 max
5086-H32	Marine grade. Medium to high strength non-heat-treatable alloy. More formable than 5083. Excellent corrosion resistance. Most often used to build boat hulls (in addition to 5052 or 6061) due to stress corrosion cracking resistance.	30,000	42,000 12% elong.	Excellent	Good	78	Al 93-96.3% Cr 0.05-0.25% Cu 0.1% max Fe 0.5% max Mg 3.5-4.5% Mn 0.2-0.7% Si 0.4% max Ti 0.15% max
6061-T6	Marine grade, often used to build boat hulls and other components. The most often used aluminum alloy for its strength, heath treatability, workability and weldability.	40,000	45,000 17% elong.	Good	Good	95	Al 95.8-98.6% Cr 0.04-0.35% Cu 0.15-0.40% Fe 0.70% Mg 0.8-1.2% Mn 0.15% max Si 0.4-0.8% Zn 0.25%
6063-T52	Softer and lower strength than 6061, good for forming, high surface finish, excellent for anodizing.	21,000	27,000	Good	Good	60	Al 97.5% max Cr 0.1% max Cu 0.1% max Fe 0.35% max Mg 0.45-0.90% Mn 0.1% max Si 0.2-0.6%
6262-T6511	Used when significant machining is required, it contains lead and bismuth to partially lubricate the cutting tool. Good strength and corrosion resistance. High surface finish possible.	27,600	31,900	Excellent	Good	71	Al 94.6-97.8% Bi 04-0.7% Cr 0.04-0.14% Cu 0.15-0.40% Fe 0.7% max Mg 0.8-1.2% Mn 0.15% max Pb 0.4-0.7% Si 0.4-0.8%
7075-T6	One of the highest strength aluminum alloys, in T6 temper higher than most mild steels. Good machinability, good corrosion resistance, good for anodizing. Used in aircraft industry.	73,000	83,000	Good	Non-weldable	150	Al 87.1-91.4% Cr 0.18-0.28% Cu 1.2-2.0% Fe 0.5% max Mg 2.1-2.9% Mn 0.3% max Zn 5.1-6.1%

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