What is Aluminum 6061
Aluminum 6061 and its alloys are implemented in most, if not all modern industrial processes due to its wide availability and the vast number of uses. An alloy is a metal made by combining two or more metallic elements to achieve improved material properties. The process of alloying involves adding specific metallic “alloying” elements into a base metal to give it distinct properties such as increased strength, corrosion resistance, conductivity, toughness, etc., or a desired combination of these traits. Alloys with low percentages of alloying elements (around <4%) are classified into wrought alloys and are workable, whereas those with higher percentages (up to 22%) are classified into cast alloys and are usually brittle. The Aluminum Association (AA Inc.) is the foremost authority on aluminum alloys and has developed a four-digit naming system used to characterize distinct wrought alloys from one another based on their main alloying elements. In this article, 6061 aluminum alloy will be discussed in detail, highlighting its physical properties as well as the common applications for this highly useful material.
Physical Properties of Aluminum 6061
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 (0.0975 lb/in3). 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. To simplify this article, the strength values for this alloy will be taken from T6 tempered 6061 aluminum alloy (6061-T6), which is a common temper for aluminum plate and bar stock. 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, and are found in Table 1. Generally, this alloy is easy to join via 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). For static applications, the yield strength is the more important design constraint as per industry standard design practices; however, the ultimate strength can be useful for certain applications that call for it. 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. As the two scissor blades close, their opposing forces act on the cross sectional plane of the paper and cause it to fail “in shear”. 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), which is calculated using 500,000,000 cycles of continuous, cyclical loading below the yield point. These values are summarized in Table 1.
Table 1: Summary of mechanical properties for 6061 aluminum alloy.
Mechanical Properties
Metric
English
Ultimate Tensile Strength
310 MPa
45000 psi
Tensile Yield Strength
276 MPa
40000 psi
Shear Strength
207 MPa
30000 psi
Fatigue Strength
96.5 MPa
14000 psi
Modulus of Elasticity
68.9 GPa
10000 ksi
Shear Modulus
26 GPa
3770 ksi
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). When in contact with alkaline soil, there may be some corrosive effects such as pitting, but this is highly dependent on soil conditions. 6061 is particularly good at resisting corrosion from concentrated nitric acid as well as ammonia and ammonium hydroxide. The corrosive effects can be removed entirely by coating the alloy with a protective layer, to which 6061 alloy responds well.
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
Summary
This article presented a brief summary of the properties, strength, and applications of 6061 aluminum. For information on other products, consult our additional guides or visit the XTJ to locate potential sources of supply or 6061 aluminum Parts . We also have guides on other types of aluminum, including 5052 Aluminum, 3003 Aluminum and 7075 Aluminum.
