Aluminum and Its Alloys

Aluminium is a kind of non-ferrous metal such as a metal that does not contain any iron contents. Non-ferrous metals are non-magnetic and resistant to corrosion. They have softness, fusibility, and ease of casting and also have special electrical properties and lower melting points. Some examples of non-ferrous metals are aluminum, copper, lead, tin, zinc, etc. 

Among all of these non-ferrous metals, aluminum possesses some special characteristics such as high ductility, machinability, conductivity, and various other features, which are important for making different parts of machines and types of equipment. 

An alloy made up of the combination of one or more non-ferrous metals in aluminum is known as aluminum alloy. It possesses some additional properties besides its parental properties due to the mixing of other components in base metal. In this chapter, we will be studying aluminum and its alloys, properties, and applications.

Aluminium

Aluminum is a soft and light non-ferrous metal, which is white in color. It is used where light, non-corrosive metal is required. It is obtained mainly from the bauxite ore. Firstly, its oxides are separated from its ore, then by an electrolytic method, it is converted into aluminum.

Properties of Aluminium

(i) It is a good conductor of electricity. 

(ii) It has good conductivity.

(iii) Its melting point is very low about 660°C. 

(iv) It is a very light metal whose density is about 2.7 g/cm³. 

(v) It is a very soft, ductile, and malleable metal.

(vi) It has very little tensile strength

(vi) It is not much affected by the environment. 

(viii) It has good resistance to corrosion

Due to poor physical and mechanical properties and high cost, non-ferrous metals are seldom (rarely) used in their pure state. But their alloy carries very good physical and mechanical properties and is widely used. In general, they have lower strength, hardness, and modulus of elasticity than iron and steel.

However, they carry their own importance due to some exceptional properties, they possess, like lightness, ease of fabrication, good machinability, good castability, high resistance to corrosion attractive appearance, etc.

Uses of Aluminium

(i) It is used for heavy conductors and bush bar work.

(ii) It is used in various domestic utensils and other heat-conducting appliances.

(iii) It is used in the manufacturing of containers for chemical industries window frames, etc.

(iv) It is widely used in the aircraft industry.

(v) It can be used in making thin sheets or wire easily.

Aluminium Alloys

Aluminum alloys are the alloys in which aluminum (Al) is the predominant metal. It is alloyed with one or more elements, to form aluminium alloy. The typical alloying elements are copper, magnesium, manganese, silicon, and zinc. The addition of small quantities of alloying elements converts the soft and weak metal into hard and strong metal, while still retaining its prime features, i.e., lightweight.

There are two principal classifications of aluminium alloys namely casting and wrought alloys. About 85% of aluminum is used for wrought products, eg, rolled plates, foils, and extrusions. Cast aluminum alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strength than wrought alloys.

The most important cast aluminum alloy system is Al-Si, where the high levels of silicon (4-13%) contribute to giving good casting characteristics. Aluminum alloys are widely used in engineering structures and components where lightweight or corrosion resistance is required. Some of the main aluminum alloys are discussed below.

1. Duralumin

It is a wrought alloy type of aluminum alloy. It contains 3.5 to 4.5% of copper, 0.4 to 0.7% of manganese, 0.4 to 0.7% of magnesium, and the remaining aluminum. This alloy possesses maximum strength (about 400 MPa) after heat treatment and age hardening (about 3 to 4 days).

It is widely used for forging, stamping, bar sheets, tubes, and rivets. It can be worked in hot conditions at a temperature of 500° C. However, after forging and annealing, it can also work in cold conditions.

2. Y-alloy

It is also called copper-aluminium alloy. The addition of copper to pure aluminum increases its strength and machinability. It contains 3.5 to 4.5% copper, 1.2 to 1.7% manganese, 1.8 to 2.3% nickel, 0.6% silicon, 0.6% magnesium, 0.6% iron and the remaining is aluminum. This alloy is also heat-treated and age-hardened like duralumin. The aging process is carried out at room temperature for about five days. It is mainly used for casting purposes. The Y-alloy has better strength than duralumin at high temperatures, therefore it is used in aircraft engines for cylinder heads and pistons.

3. Magnalium

It is made by melting the aluminum with 2 to 10% magnesium in a vacuum and then cooling it in a vacuum or under a pressure of 100 to 200 atmospheres. It also contains 1.75% of copper. Due to its lightweight and good mechanical properties, it is mainly used for aircraft and automobile components.

4. Hindalium

It is an alloy of aluminum and magnesium with a small quantity of chromium. It is the trade name of aluminum alloy produced by Hindustan Aluminium Corporation Ltd. It is produced as a rolled product in 16 gauge, mainly for anodized utensil manufacture.

Properties of Aluminium Alloy 

The properties of aluminum alloys are as follows.

(i) It is light in weight.

(ii) It is corrosion resistance.

(iii) It has good casting characteristics. 

(iv) It is used in engineering structures.

(v) It does not rust easily. 

(vi) It has a lower fatigue rate.

(vii) It has higher tensile strength.

Uses of Aluminium Alloy 

(i) It is used for making aircraft components.

(ii) Due to its lightweight, it is also used for making automobile components.

(iii) It can be extruded to form complete profiles. 

(iv) Stiffer and lighter design can be achieved with aluminum alloys.

(v) It can be used to form rolled plates, foils, extrusions, etc.

Advantages and Disadvantages of Aluminium Alloy 

Advantages

(i) It has a longer life span than aluminum.

(ii) It has a lower fatigue rate.

(iii) A wide range of different alloys is available for different uses. 

(iv)It has better characteristics like low density, higher tensile strength, lighter weight, etc.

(v) It has a better weight/strength ratio.

Disadvantages

(i)High cost to manufacture

(ii) Dangerous if not tested properly. 

Like aluminum alloy, steel is an alloy made from the mixing of ferrous metal iron, and carbon. The percentage content of carbon in steel varies from 0.002 to 2.1% So, let us compare between the aluminium alloy and steel.

Comparison between Aluminium Alloy and Steel