What is 6061 Aluminum Alloy?

Physical Properties of 6061 Aluminum

Type 6061 aluminum is of the 6xxx aluminum alloys, which entails those mixtures which use magnesium and silicon as the primary alloying elements. The second digit indicates the degree of impurity control for the base aluminum. When this second digit is a “0”, it indicates that the bulk of the alloy is commercial aluminum containing its existing impurity levels, and no special care is needed to tighten controls. The third and fourth digits are simply designators for individual alloys (note that this is not the case with 1xxx aluminum alloys). The nominal composition of type 6061 aluminum is 97.9% Al, 0.6% Si, 1.0%Mg, 0.2%Cr, and 0.28% Cu. The density of 6061 aluminum alloy is 2.7 g/cm3. 6061 aluminum alloy is heat treatable, easily formed, weld-able, and is good at resisting corrosion.

Mechanical Properties

The mechanical properties of 6061 aluminum alloy differ based on how it is heat treated, or made stronger using the tempering process. Its modulus of elasticity is 68.9 GPa (10,000 ksi) and its shear modulus is 26 GPa (3770 ksi). These values measure the alloy’s stiffness, or resistance to deformation, you can found in Table 1. Generally, this alloy is easy to join by welding and readily deforms into most desired shapes, making it a versatile manufacturing material.

Two important factors when considering mechanical properties are yield strength and ultimate strength. The yield strength describes the maximum amount of stress needed to elastically deform the part in a given loading arrangement (tension, compression, twisting, etc.). The ultimate strength, on the other hand, describes the maximum amount of stress a material can withstand before fracturing (undergoing plastic, or permanent deformation). 6061 aluminum alloy has a yield tensile strength of 276 MPa (40000 psi), and an ultimate tensile strength of 310 MPa (45000 psi). These values are summarized in Table 1.

Shear strength is the ability of a material to resist being sheared by opposing forces along a plane, just as a scissor cuts through paper. This value is useful in torsional applications (shafts, bars etc.), where twisting can cause this kind of shearing stress on a material. The shear strength of 6061 aluminum alloy is 207 MPa (30000 psi), and these values are summarized in Table 1.

Fatigue strength is the ability of a material to resist breaking under cyclical loading, where a small load is repeatedly imparted on the material over time. This value is useful for applications where a part is subject to repetitive loading cycles such as vehicle axles or pistons. The fatigue strength of 6061 aluminum alloy is 96.5 Mpa (14000 psi). These values are summarized in Table 1.

Table 1: Summary of mechanical properties for 6061 aluminum alloy.

Corrosion Resistance

When exposed to air or water, 6061 aluminum alloy forms a layer of oxide which renders it nonreactive with elements that are corrosive to the underlying metal. The amount of corrosion resistance is dependent upon atmospheric/aqueous conditions; however, under ambient temperatures, corrosive effects are generally negligible in air/water. It is important to note that due to the copper content of 6061, it is slightly less resistant to corrosion than other alloy types (such as 5052 aluminum alloy, which contains no copper). 6061 is particularly good at resisting corrosion from concentrated nitric acid as well as ammonia and ammonium hydroxide.

Applications of Type 6061 Aluminum

Type 6061 aluminum is one of the most widely used aluminum alloys. Its weld-ability and formability make it suitable for many general-purpose applications. Its high strength and corrosion resistance lend type 6061 alloy particularly useful in architectural, structural, and motor vehicle applications. Its list of uses is exhaustive, but some major applications of 6061 aluminum alloy include:

• Welded assemblies
• Marine frames
• Aircraft and truck frames
• Chemical equipment
• Electronic parts
• Furniture
• Fasteners
• Heat Exchangers
• Heat Sinks