Among all of the available grades of aluminum, 3003 is the most common aluminum alloy used for various general-purpose applications due to its decent strength and good workability. With manganese as the primary alloying element, 3003 scores excellent in terms of formability and corrosion resistance as compared to other aluminum metals and tempers. However, when it comes to strength, 6061, another commonly used aluminum alloy, triumphs over 3003 with more yield strength, which is useful for designing structural applications.

It’s important to know which is the best variant when machining aluminum. Below, we detail the wide range of mechanical properties of 3003 and 6061 aluminum and discuss the applications in which each alloy excels.

Understanding the 3003 Aluminum Alloy

3003 is an aluminum-manganese copper alloy that is moderately strengthened by cold hardening. Manganese is the main alloying element in the 3003 aluminum alloys, with its percentage varying between 1% and 1.5%, depending on how the aluminum alloy is fabricated. The presence of copper and magnesium offers 20% additional strength than 1100-grade aluminum, yet it is labeled as a moderately strong material due to its low tensile and yield strengths.

The table below shows the typical strength of different 3003 tempers.

3003 tempers	Maximum Ultimate Strength (KSI)	Maximum Yield Strength (KSI)
3003-O	19	6
3003-H12	23	18
3003-H14	26	21
3003-H16	30	25
3003-H18	27	27

Apart from moderate strength, 3003 aluminum alloys are corrosion resistant, workability, and weldability. Thus, it is an ideal light structure material, globally acknowledged as the most common aluminum alloy or general-use alloy. The most common applications of 3003 occur in the aerospace, food, and chemical industries.

Some popular applications include the following:

• Gutters.
• Folded sheets.
• Storage containers.
• Truck roofs.
• Radiators.
• Pressure vessels.
• Acoustic ceilings.
• Downspouts.

Despite all of these advantages, machining 3003 can prove challenging. Though 3003 tempers have fair machinability, they are less machinable than other harder aluminum alloys. They also are not heat treatable, which means, unlike heat-treated metals, they can not achieve a secondary phase of precipitation hardening required for improved strength.

As a cold-treated metal, 3003 aluminum alloys are also prone to hydrogen-induced porosity during welding. The best way to avoid this situation is to drop hydrogen pickup to a low level while welding. This is another major reason why 3003 cannot be used for extreme environment applications.

Understanding the 6061 Aluminum Alloy

6061 aluminum alloys are extremely versatile, containing silicon and magnesium as major alloying elements. These different aluminum alloys display excellent corrosion resistance and a good strength-to-weight ratio, highly sought-after mechanical properties for building marine and aerospace structures. With good electrical and thermal conductivity, 6061 plates find broad applications in electrical fittings, connectors, and magneto parts as well.

6061 aluminum alloys are heat-treated and thus are available in different tempers, such as F, O, W, and T. In this regard, the 6061-Tx variant has many applications. In 6061-Tx, the letter “T” represents temper, and “x”, usually represented as a digit, indicates whether the alloy has received any special treatment.

For instance, 6061-T6 aluminum alloys are solution heat-treated and artificially aged to offer good machinability and excellent weldability. However, it has poor formability. If you need good formability from a 6061 alloy, 6061-T4 would be an ideal choice, as it is naturally aged to have good formability and excellent weldability. In short, different 6061 tempers can meet wide application requirements, unlike 3003 tempers.

6061 aluminum alloys are commonly used in the following:

• Bicycle frames.
• Cans.
• Truck frames.
• Towers and pylons.
• Aircraft applications.
• Rail coaches.

The Most Common Aluminum Alloy for Machining: 6061 or 3003?

For a quick comparison, the table below lists the essential elements of 6061 and 3003.

Property	Aluminum 6061	Aluminum 3003
Ultimate Tensile Strength	310 MPa	200 MPa
Yield Strength	276 MPa	186 MPa
Shear Strength	207 MPa	110 MPa
Brinell Hardness	95 HB	28 HB
Machinability	Good	Acceptable
Formability	Poor	Good
Weldability	Good	Good
Workability	Heat: Good	Cold: Very Good

In terms of formability, 3003 is a better choice over 6061, especially if the application requires good formability to meet design requirements. For example, 3003 is an excellent choice for outdoor decorative architecture that requires formability coupled with moderate strength for a good aesthetic appeal.

However, as a cold-treated alloy, it is not suitable for structural applications requiring heavy machining. A majority of aluminum production is intended for structural applications, such as body frames and parts, for the automobile and aerospace industries to achieve an improved strength-to-weight ratio. In this regard, 6061 is one of the most common machinable alloys that meet a wide range of application requirements.

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