In the wrought alloy designation system, what does the number 2xxx indicate?

In the wrought alloy designation system, the number series indicates the primary alloying element in the aluminum alloy. Specifically, the "2xxx" series is primarily associated with copper as the major alloying element. This classification means that alloys in this group typically contain significant amounts of copper, which gives them various advantageous properties such as increased strength, improved machinability, and better fatigue resistance compared to aluminum alone.

Copper as an alloying element also influences the material's performance, particularly at elevated temperatures, making 2xxx alloys suitable for applications in aerospace and other high-performance sectors. The use of copper also affects attributes like corrosion resistance, which is typically lower than in other aluminum series (such as those alloyed with magnesium or silicon). This makes 2xxx series alloys particularly suitable for applications where strength-to-weight ratios are critical, such as in aircraft structures.

Understanding this classification helps in selecting the appropriate material for specific applications in the aerospace field.