2024 - Alloyed with 4.5% copper. Fair workability and corrosion resistance. Used for structural applications. Tensile strength between 30,000 to 63,000 psi.
Copper is the main alloying ingredient in 2024. It is very strong compared to most
Aluminium alloys, and has average machinability, but the copper component of this alloy makes it susceptible to
corrosion (many items in this alloy are produced with a clad surface to protect the underlying material.) In addition, 2024 is not considered to be weldable. Finally, the
fatigue resistance of 2024 make it a primary choice when the application is expected to be under stress or strain for prolonged periods. It is commonly used in aerospace applications.
Principal Design Features
An age hardening, high strength Aluminium alloy. Useful for optimum strength to weight ratio structures.
Applications
Commonly used in the manufacture of truck wheels, aircraft structures, and screw machine products, scientific instruments, veterinary and orthopedic braces and equipment, and in rivets.
Machinability
The machining characteristics of AL 2024 are fair in the heat treated condition, which is the condition in which most machining is done. Machinability in the annealed condition is good. Use of oil lubricants is recommended for all machining operations.
Forming
The alloy may be formed by conventional methods, except that hot forming should be avoided - see "Hot Working".
Welding
Welding may be done by use of resistance welding or inert gas consumable electrode arc method. However it must be noted that, in general, welding by any means is NOT recommended for this alloy because of the degradation of corrosion resistance that occurs as a result of weld heat. A repeat heat treatment should be done if welded.
Heat Treatment
This is an age-hardening alloy and responds to heat treatment to accomplish the strengthening (aging). See "Annealing" and " Aging". The T4 condition is attained by a 920 F heating followed by cold water quench and aging at room temperature. T6 by the same 920 F and quench followed by 375 F for 10 hours and air cooling.
Forging
The alloy may be forged. However subsequent heat treatment is necessary in order to retain reasonable corrosion resistance.
Hot Working
Hot forming should be avoided if possible because of the harmful effect of heating upon corrosion resistance. If, for example, T4 condition is hot worked it is the necessary to age the part to the T6 condition to restore corrosion resistance.
Cold Working
Cold working of this alloy is readily done by conventional methods. Ductility In the annealed condition is best and bend radii of 1/2 to 1 times thickness are possible for sheet 1/4 " thick, or thinner. For T3 or T4 conditions bend radii of 5 to 6 times thickness are required.
Annealing
Annealing is done at 750 to 800 F for at least 2 hours at temperature, followed by slow cooling in the furnace. This will anneal the alloy from a heat treated condition. Annealing between cold work operations may be done at 650 F for 2 hours, followed by air cooling.
Aging
The T4 condition is attained by a 920 F heating and cold water quench. Aging then occurs at room temperature. For T6 condition use the same 920 F and water quench procedure then reheat to 375 F for 10 hours and air cool. Other conditions are a result of the T4 condition followed by controlled amounts of cold working.
Hardening
Hardening, or strengthening, occurs from a solution anneal and aging at room temperature or varying amounts of cold working,
Other Physical Props
Electrical conductivity is 35% that of copper.
Other Mechanical Props
Shear strength in the annealed condition is 18 ksi. For T3 and T4 condition it is much stronger, 41 ksi.
