AlCu

AlCu refers to aluminum-copper alloys, a class of high-strength, heat-treatable aluminum alloys in which copper is the principal alloying element. The most common family is the 2XXX series, widely used where high strength is required relative to weight, such as in aerospace structures and ground transport components. Compared with other aluminum alloys, AlCu alloys generally offer superior strength after aging but lower corrosion resistance and weldability.

Composition and microstructure: AlCu alloys typically contain copper in the range of a few percent by weight, with additional elements such as magnesium, silicon, manganese, or zirconium to improve aging response or grain structure. The strengthening mechanism is precipitation hardening: copper-rich precipitates, such as theta (Al2Cu) phases, form during aging and hinder dislocation motion in the aluminum matrix.

Processing and temper designations: They are solution heat treated, quenched, and aged to produce strengthening precipitates. Common tempers include T6 (solution heat-treated and artificially aged) and T4 or T3 (varying natural or artificial aging and work hardening). These alloys are typically wrought products such as sheets, plates, extrusions, and forgings.

Properties and limitations: AlCu alloys show high strength-to-weight ratios and good fatigue performance in the right temper. They have relatively poor corrosion resistance, especially in aggressive environments, and can be susceptible to stress-corrosion cracking and hydrogen embrittlement in some conditions. Weldability is generally limited, and joining often requires special precautions or coatings.

History and uses: Development of heat-treatable Al-Cu alloys began in the early 20th century, with widespread adoption in the 2XXX family for aerospace and high-stress components. Today they are used in aircraft structures, structural components in harsh environments, and other applications where light weight and high strength are essential.