Aluminium and Aluminium Alloys

Aluminium is the most commonly used and commercially available metal. It’s light weight and high strength-to-weight ratio make it a good choice for everything from aircraft to flashlights to jigs to just about anything else you can make out of metal. Pure aluminium, primarily seen in the 1xxx series of wrought aluminium alloys, has little strength, but possesses high electrical conductivity, reflectivity, and corrosion resistance. So a wide variety of aluminium alloys have been developed.

aluminium is a silverish white metal that has a strong resistance to corrosion and like gold, is rather malleable. It is a relatively light metal compared to metals such as steel, nickel, brass, and copper with a specific gravity of 2.7. aluminium is easily machinable and can have a wide variety of surface finish. It also has good electrical and thermal conductivities and is highly reflective to heat and light. At extremely high temperatures (200-250°C) aluminium alloys tend to lose some of their strength. However, at subzero temperature, their strength increases while retaining their ductility, making aluminium an extremely useful low-temperature alloy.

Aluminium alloys have a strong resistance to corrosion which is a result of an oxide skin that forms as a result of reactions with the atmosphere. This corrosive skin protects Aluminium from most chemicals, weathering conditions, and even many acids, however alkaline substances are known to penetrate the protective skin and corrode the metal.

Aluminium also has a rather high electrical conductivity, making it useful as a conductor. Copper is the more widely used conductor, having a conductivity of approximately 161% that of Aluminium. Aluminium connectors have a tendency to become loosened after repeated usage leading to arcing and fire, which requires extra precaution and special design when using Aluminium wiring in buildings.

Aluminium is a very versatile metal and can be cast in any form known. It can be rolled, stamped, drawn, spun, roll-formed, hammered and forged. The metal can be extruded into a variety of shapes, and can be turned, milled, and bored in the machining process. Aluminium can riveted, welded, brazed, or resin bonded. For most applications, Aluminium needs no protective coating as it can be finished to look good, however it is often anodized to improve color and strength.

1100 | 3003 | 5005 | 5052 | 5083 | 5086 | 5454 | 2011 | 2024 | 6061 | 6101 | 6063 | 6262 | 7075 | Aluminium | Aluminium Tempers | CEN Identification | Pure Aluminium | Work Hardening | Heat Treatable | Mechanical Properties of Aluminium Alloys | Physical Properties of Aluminium Alloys | Aluminium Alloys Chemical Composition | Specifications Standard | Aluminum Corrosion Resistance for Plate-Fin Heat Exchangers | Aluminium Tubing strength for Mechanics | Aluminium Alloys Comparison Table | Aluminium Density Specific Gravity

Non Heat Treatable Alloys

1100 – Commercially pure aluminum. Excellent corrosion resistance, workability and weldability.  14,000 to 24,000 psi .

3003 – Alloyed with 1,2% manganese.  Very Good workability, weldability and corrosion resistance. Tensile strength range 17,000 to 30,000 psi .

5005 – Alloyed with .8% magnesium. Excellent workability, weldability and corrosion resistance. Tensile strength range 18,000 to 30,000 psi .

5052 – Alloyed with 2.5% magnesium. Very good corrosion resistance, good workability, weldability and strength. Tensile strength between 31,000 to 44,000 psi.

5083 – Alloyed with 4.45% magnesium, .65 % manganese and .15% chromium. Excellent weldability, light weight and good =corrosion resistance. Tensile strength between 40,000 to 59,000 psi .

5086 – Alloyed with 4.0% magnesium, .45% manganese and .15% chromium. Very good corrosion resistance, good workability. Tensile strength between 40,000 to 54,000 psi.

5454 – Alloyed with 2.7% magnesium, 0.8% manganese and 0.12% chromium. Good formability, weldability and corrosion resistance. Often used for pressure vessels. Tensile strength between 36,000 to 47,000 psi.

Heat Treatable Alloys

2011– is the most machinable of the commonly available aluminum alloys.

2024 – Alloyed with 4.5% copper. Fair workability and corrosion resistance. Used for structural applications.  Tensile strength between 30,000 to 63,000 psi.

6061 – alloyed with 1.0% magnesium and 0.6% silicon.  Good formability, weldability and corrosion resistance.  Very good machine-ability.  Yield between 7,000 to 39,000 psi.

6101 is best suited for applications involving moderate strength and maximum electrical conductivity.

6063 – Good Formability, often called architectural aluminum

6262 was designed as an aluminum alloy for operations where significant machining is required.

7075 – Alloyed with zinc, magnesium, copper and chromium.  Poor formability, good machine ability.  Yield between 32,000 and 76,000 psi.

The properties of aluminum that contribute to its widespread use are:

• Aluminum is light; its density is only one-third that of steel.
• Aluminum is resistant to weather, common atmospheric gases, and a wide range of liquids.
• Aluminum can be used in contact with a wide range of foodstuffs.
• Aluminum has a high reflectivity and, as a result, is employed in a number of decorative applications.
• Aluminum alloys can equal or even exceed the strength of normal construction steel.
• Aluminum has high elasticity, which is an advantage in structures under shock loads.
• Aluminum keeps its toughness down to very low temperatures, without becoming brittle like carbon steel.
• Aluminum is easily worked and formed; it can be rolled to very thin gauge.
• Aluminum conducts electricity and heat nearly as well as copper.

Pure aluminium is soft, ductile, corrosion resistant and has a high electrical conductivity, see Table 1. In consequence it is widely used for foil and conductor cables, but alloying with other elements is necessary to provide the higher strengths needed for other applications.

Table 1. Typical properties for aluminium

Designations for Wrought and Cast Aluminium Alloys

The main alloying elements are copper, zinc, magnesium, silicon, manganese and lithium. Small additions of chromium, titanium, zirconium, lead, bismuth and nickel are also made and iron is invariably present in small quantities. There are over 300 wrought alloys with 50 in common use. They are normally identified by a four figure system which originated in the USA and is now universally accepted. Table 2 describes the system for wrought alloys. Cast alloys have similar designations and use a five digit system (table 2). Table 3 lists the designations, characteristics, common uses and forms of some widely used alloys.

Table 2. Designations for alloyed wrought and cast aluminium alloys.

Table 3. Some common aluminium alloys, their characteristics and common uses.

Where: * = most commonly used alloys, S = sheet, P = plate and E = extrusionsDesignations for Wrought Alloys

These alloys fall into two distinct categories

1. Those which derive their properties from work hardening.
2. Those which depend upon solution heat treatment and age hardening.Work Hardened Aluminium Alloys

The 1000, 3000 and 5000 series alloys have their properties adjusted by cold work, usually by cold rolling.

The properties of these alloys depend upon the degree of cold work and whether any annealing or stabilising thermal treatment follows the cold work. A standardised nomenclature is used to describe these conditions.

It uses a letter, O, F or H followed by one or more numbers. It is presented in summary form in Table 4 and defined in Table 6.

Table 4. Standard nomenclature for work hardened aluminium alloys.

Table 5. Explanations of symbols used in table 4.

To illustrate this, by reference to Tables 2 and 4, we can see that 3103-0 is an aluminium manganese alloy in the soft annealed condition and 3103-H16 is the same alloy three quarters hard.

With the flexibility of compositions, degree of cold work and variation of annealing and temperature a wide range of mechanical properties can be achieved especially in sheet products.Solution Heat Treated and Age Hardened Aluminium Alloys

The 2000, 4000, 6000, 7000 and 8000 series alloys respond in this way.

The wide choice of alloy compositions, solution heat treatment temperatures and times, quench rates from temperature, choice of artificial ageing treatment and degree to which the final product has been deformed permit a wide range of properties to be achieved. A system of standard designations is used, based upon the letter T followed a number after the alloy designation, to describe the various conditions. These are defined in Table 6.

Table 6. Definition of heat treatment designations for aluminium and aluminium alloys.