2024 Aluminum Alloy: Know its Properties and Machining Methods

2024 aluminum properties are due to its chemical composition and are dividable into physical, mechanical, and others. Furthermore, the properties vary based on heat tempering, leading to the need to understand the material to aid their use.

Physical Properties

The physical 2024 aluminum properties give information about its behavior and suitability for its intended applications. The physical properties of aluminum 2024 are:

• Density: Aluminum alloy 2024 has a density of 2.78g/cm3. This is low (slightly higher than pure aluminum 2.7g/cm3), meaning the material can provide strength without adding weight.
• Thermal Conductivity: Its thermal conductivity is about 120 W/(m·K). As a result, it is important in parts needing faster heat dissipation, especially in aircraft engines.
• Electrical Conductivity: 2024 Aluminum alloy has an electrical conductivity of 30% IACS due to the presence of copper, although it is not as conductive as its primary alloying element (copper).
• Coefficient of Thermal Expansion (CTE): Aluminum 2024 has a moderate CTE (23.2 µm/m°C), meaning its dimension does not change much with increased temperature. Hence, manufacturers can predict the material’s expansion and contraction and reduce the risk of part failure due to temperature change.
• Machinability: Aluminum 2024 alloy is highly machinable, i.e., compatible with machining operations such as cutting, drilling, turning, etc. Furthermore, it has high working, which allows easier cutting and extrusion. Its excellent workability and machinability make it a valuable material in aerospace and automotive sheet metal fabrication.

Mechanical Properties

The alloy’s mechanical properties describe its response to mechanical forces or loads. These include:

• Tensile Strength: 2024 aluminum has a tensile strength of 290 – 450 MPa (42,100 – 65,300 psi). This shows that it withstands a huge force during pulling or stretching before breaking. Furthermore, it makes it applicable in making parts with load-bearing/structural attributes.
• Yield Strength: Its yield strength is 195-415 MPa (28,300-60,000 psi). This means that it requires much stress to undergo irreversible plastic deformation. As a result, it is applicable in making parts with structural applications.
• Hardness: Its hardness depends on the heat temper, ranging from 50HB to 120HB. Furthermore, it measures its resistance to deformation, abrasion, and scratching and can guide manufacturers in the applications of 2024 aluminum alloy.
• Fatigue Strength: 2024 aluminum alloy has good fatigue strength (138 MPa or 20,000 psi), calculated with 500,000,000 loading cycles under the yield point. As a result, one of the applications of 2024 aluminum alloy is making parts that can withstand cyclic loading or repeated stress.
• Shear Strength: Shear strength is a measure of the aluminum 2024 alloy to shearing stresses or cutting stresses. It has a value of 283 MPa (41,000 psi), which is moderately strong.

Below is a summary chart of the 2024 aluminum properties with differences based on its common heat tempers:

Aluminum 2024 excellent properties make it a popular industrial material. Below are several processing and manufacturing methods for making the alloy.

Alloying and Casting

The chemical composition of aluminum alloy 2024 is copper, magnesium, manganese, and other elements like silicon and iron in 0.3%.

The 2024 aluminum manufacturing process starts with casting. Aluminum ingots and alloying elements are melted in a furnace, and the molten form is cast into various shapes. The casting method can be continuous casting or ingot casting, and the choice of casting method depends on the requirement and shape of the final product.

Heat Treatment

Heat tempering is a process that strengthens a metal or its alloy. It includes processes such as:

• Solution heat treatment allows the alloying elements to dissolve into the aluminum matrix and give a homogeneous microstructure. It occurs at a high temperature (typically 480°C to 495°C) with the temperature held for a predetermined time.
• Quenching is a controlled and rapid cooling of the alloy after heat treatment. It results in freezing the alloy’s microstructure and prevents the formation of large precipitates.
• Aging is another process that alloy 2024 is subjected to, leading to a different temper. It can be natural, as seen in (T3) or occurs at a lower temperature (typically 120°C and 190°C). This leads to the precipitation of fine particles within the aluminum matrix and increases the alloy’s strength and hardness.
• Cold working involves shaping the alloy 2024 when cold using techniques such as rolling, extrusion, and drawing. This increases the alloy’s strength, and it can afterward be subjected to machining techniques such as milling and turning.

Due to heat tempering, aluminum 2024 alloy has slightly different mechanical properties. Each temper has a designator, “Tx” where x is a one-to-five digit that encodes the properties of the alloy.

The first digit indicates the heat treatment method, while the second-to-fifth digits indicate specific manufacturing qualities. For example, in the T42 temper, 4 denotes solution heat-treating and natural aging, and “2” denotes that the buyer must heat-treat the metal themselves.

However, it is confusing, manufacturers must talk to experts who know about the properties of the alloy. Common tempers of the 2024 aluminum alloy include:

2024-T3

2024-T3 undergoes a solution heat treatment at about 4850C, cold working (or cold rolling), and natural aging at room temperature. It has an ultimate tensile strength of 400–430 MPa (58-62 ksi) and yield strength of 270–280 MPa (39-40 ksi). Its good formability and strength make it suitable for making complex-shaped parts.

2024-T4

T4 temper alloy undergoes solution heat treatment and natural aging at room temperature. This leads to improved ductility and formability. As a result, they are applicable in making parts that require better shaping abilities without reducing strength.

2024-T6

This alloy underwent solution heat treatment, then artificial aging at about 190-205°C (375-400°F). This makes it the strongest and hardest temper. As a result, it is suitable for making parts where strength is critical.

2024-T62

This T6 2024 aluminum alloy underwent stabilization heat treatment after artificial aging. As a result, it has better stress corrosion cracking resistance. Furthermore, this makes it suitable for parts used in corrosive environments.

2024-O

This 2024 aluminum alloy did not undergo heat tempering but underwent a full annealing. This increases its formability but reduces its strength compared to the other tempers, and it has an ultimate tensile strength of 140 – 210MPa and a maximum yield strength of 97 MPa (14,000 psi). It is suitable for making parts that require flexibility.

Cold Working and Machining

Cold working methods include rolling, extrusion, and drawing, increasing aluminum 2024 strength and other mechanical properties. Furthermore, they can shape the alloy into the desired design. Aluminum alloy 2024 is also highly machinable using conventional machining techniques, such as milling, turning, and drilling.

Welding

Aluminum 2024 alloy is also subjectable to welding techniques such as TIG welding, resistance spot welding, and friction stir welding. Welding aluminum 2024 is critical due to its tendency to suffer from microcracking. As a result of its poor weldability, riveting and adhesive bonding are more common joining techniques.