Why must rivets of a 2017 aluminum alloy be refrigerated before they are used?

2017 aluminum alloy is widely used in the manufacturing of aircraft structural components and rivets. It has excellent machinability, good mechanical properties, and reasonable corrosion resistance. The rivets made from this alloy are usually refrigerated before use, which significantly improves their performance and durability.

Aluminum alloys contain a combination of aluminum and other elements, which enhances their properties compared to pure aluminum. 2017 aluminum alloy primarily consists of aluminum, copper, magnesium, and smaller amounts of other elements such as silicon and manganese. The addition of these elements changes the molecular structure of the alloy, forming a stable and strong bond between the atoms.

Refrigeration before usage is crucial to improve the mechanical properties and performance of rivets of a 2017 aluminum alloy. In refrigeration, the temperature of the rivets is reduced, typically around -18°C to -40°C. This lower temperature results in two essential changes in the aluminum alloy: 1. Atomic arrangement: At lower temperatures, the atoms in the alloy rearrange themselves and get closer, resulting in a more densely packed and compact structure. This rearrangement makes the alloy stronger and more resistant to deformation. 2. Aging: One significant property of 2017 aluminum alloy is natural or artificial aging. Refrigeration increases the rate of precipitation, where copper atoms cluster together to form small, finely dispersed particles within the aluminum matrix. These particles strengthen the aluminum matrix by hindering dislocation movement, which in turn, increases the alloy's hardness, strength, and durability.

There are several benefits to using refrigerated rivets of a 2017 aluminum alloy: 1. Increased strength: As mentioned earlier, refrigeration enhances the mechanical properties of the alloy, making it stronger and more robust. 2. Improved working: Refrigerated rivets become more malleable and ductile, allowing for easier forming and joining processes without the risk of cracking or breaking. 3. Enhanced corrosion resistance: The more densely packed structure that results from refrigeration makes the alloy more resistant to corrosion due to reduced susceptibility to intergranular corrosion. In conclusion, refrigeration of 2017 aluminum alloy rivets is vital to ensure their optimal performance and durability. This process improves their mechanical properties and makes them more suitable for use in high-stress environments, such as aircraft construction.