Aluminium Properties

As with other metallic hardware, aluminum fasteners are mixes of various materials to make an alloy. Luckily, only a few of the numerous possible alloys are used in your common stock fasteners. The three most common aluminum alloys found in fasteners are 2024-T4, 6061-T6, and 7075-T6.
Before describing each alloy’s properties, we’ll outline characteristics common across all three.

• ☆ Each aluminum alloy is a non-ferrous mix of metals including pure aluminum, iron, silicon, copper, magnesium, manganese, and zinc. Changing the proportion of the various additive metals results in changes to the alloy’s strength, workability, corrosion resistance, and electrical conductivity.
• ☆ All alloys are relatively lightweight, lower density, and naturally more corrosion resistant when compared to steel (more on this below).
• ☆ All alloys are heat treated to give additional strength and durability, defined by the “-T4” or “-T6” temper designators at the end of the alloy number.
• ☆ All alloys are non-toxic, non-magnetic, non-sparking, odorless, impermeable, and recyclable.
• ☆ And finally, all alloys are very good heat and electrical conductors.

Comparing to Steel Fasteners

A topic frequently overlooked when discussing aluminum fasteners is how they stack up against common steel fasteners. We often see applications where aluminum may have been a fine choice, however steel was selected simply because it’s more commonly known. The ‘zinc plated steel’ section at your local hardware store is likely much larger than the aluminum section, and we think this reflects the general perception that aluminum is for special jobs only.

Let’s take a quick look at the differences here. When compared to steel, aluminum features:

• ☆ Competitive Cost – pound for pound, general carbon steel alloys are typically less expensive than aluminum alloys. The difference is however usually low, and is often offset by the lighter weight and omission of adding a protective finish.
• ☆ Lighter weight – you’ll gain lower total weight than steel in aluminum fasteners, just be sure to check that the strength values of the aluminum option meet the needs of the project when directly replacing steel.
• ☆ Higher malleability – aluminum fasteners can handle more cyclic and elastic stresses, and can be more easily formed / machined.
• ☆ Low temperature performance – aluminum is excellent at maintaining strength at low temperatures, whereas steel becomes brittle and can lose strength.
• ☆ Lifespan – since the carbon in steel materials is susceptible to corrosion and decay, aluminum typically has a longer lifespan with less maintenance required than steel.
• ☆ Higher corrosion resistance – aluminum naturally forms a protective oxide layer on its surface, offering integral corrosion resistance, where steel has no such capability and must have a finish applied to protect it.
  Aluminum is not for every project but has plenty of unique features that can benefit many applications where steel might otherwise be the default selection.

Chemical Composition Limits for Aluminum Alloys

Typical Mechanical Properties