Aluminum

A metal which is commonly used for its light weight property while still being somewhat strong.

How to Read Aluminum Alloy Designations

Wrought Alloy Designation System

First Digit

The first digit (Xxxx) indicates the principal alloying element, which has been added to the aluminum alloy and is often used to describe the aluminum alloy series, i.e., 1000 series, 2000 series, 3000 series, up to 8000 series. See the table below.

Second Digit

The second single digit (xXxx), if different from 0, indicates a modification of the specific alloy.

Third and Fourth Digit

The third and fourth digits (xxXX) are arbitrary numbers given to identify a specific alloy in the series.

Example

In alloy 5183, the number 5 indicates that it is of the magnesium alloy series, the 1 indicates that it is the 1st modification to the original alloy 5083, and the 83 identifies it in the 5xxx series.

Notes

The only exception to this alloy numbering system is with the 1xxx series aluminum alloys (pure aluminums) in which case, the last 2 digits provide the minimum aluminum percentage above 99%, i.e., Alloy 1350 (99.50% minimum aluminum).

Alloy Series	Principal Alloying Element
1xx	99.000% Minimum Aluminum
2xx	Copper
3xx	Manganese
4xx	Silicon
5xx	Magnesium
6xx	Magnesium and Silicon
7xx	Zinc
8xx	Other Elements

Cast Aluminum Designation System

The cast alloy designation system is based on a 3 digit-plus decimal designation xxx.x (i.e. 356.0).

First Digit

The first digit (Xxx.x) indicates the principal alloying element, which has been added to the aluminum alloy.

Second Digit and Third Digit

The second and third digits (xXX.x) are arbitrary numbers given to identify a specific alloy in the series.

Fourth Digit

The number following the decimal point indicates whether the alloy is a casting (.0) or an ingot (.1 or .2). A capital letter prefix indicates a modification to a specific alloy.

Example

Alloy - A356.0 the capital A (Axxx.x) indicates a modification of alloy 356.0. The number 3 (A3xx.x) indicates that it is of the silicon plus copper and/or magnesium series. The 56 (Ax56.0) identifies the alloy within the 3xx.x series, and the .0 (Axxx.0) indicates that it is a final shape casting and not an ingot.

Alloy Series	Principal Alloying Element
1xx.x	99.000% minimum Aluminum
2xx.x	Copper
3xx.x	Silicon Plus Copper and/or Magnesium
4xx.x	Silicon
5xx.x	Magnesium
6xx.x	Unused Series
7xx.x	Zinc
8xx.x	Tin
9xx.x	Other Elements

The Aluminum Temper Designation System

Letter	Meaning''''
F	As fabricated – Applies to products of a forming process in which no special control over thermal or strain hardening conditions is employed.
O	Annealed – Applies to product which has been heated to produce the lowest strength condition to improve ductility and dimensional stability.
H	Strain Hardened – Applies to products which are strengthened through cold-working. The strain hardening may be followed by supplementary thermal treatment, which produces some reduction in strength. The “H” is always followed by two or more digits. The first digit after the H indicates a basic operation.The second digit after the H indicates the degree of strain hardening.
	H1X	Strain Hardened
	H2X	Strain Hardened and Partially Annealed
	H3X	Strain Hardened and Stabilized
	H4X	Strain Hardened and Lacquered or Painted
	HX2	Quarter Hard
	HX4	Half Hard
	HX6	Three Quarter Hard
	HX8	Full Hard
	HX9	Extra Hard
W	Solution Heat-Treated – An unstable temper applicable only to alloys which age spontaneously at room temperature after solution heat-treatment
T	Thermally Treated - To produce stable tempers other than F, O, or H. Applies to product which has been heat-treated, sometimes with supplementary strain-hardening, to produce a stable temper. The “T” is always followed by one or more digits.Additional digits indicate stress relief by either stretching or compressing.
	T1	Naturally aged after cooling from an elevated temperature shaping process, such as extruding.
	T2	Cold worked after cooling from an elevated temperature shaping process and then naturally aged.
	T3	Solution heat treated, cold worked and naturally aged.
	T4	Solution heat treated and naturally aged.
	T5	Artificially aged after cooling from an elevated temperature shaping process.
	T6	Solution heat treated and artificially aged.
	T7	Solution heat treated and stabilized (overaged).
	T8	Solution heat treated, cold worked and artificially aged.
	T9	Solution heat treated, artificially aged and cold worked.
	T10	Cold worked after cooling from an elevated temperature shaping process and then artificially aged.

Fatigue Analogy: Aluminum runs short sprints while steel does marathons.

1000 Series

The 1000 series has "excellent corrosion resistance, high thermal and electrical conductivity, low mechanical properties, and excellent workability.These alloys have relatively poor mechanical properties and would seldom be considered for general structural applications.

1100

Used in soft solid rivets.

2000 Series

The 2000 series is generally heat-treated for optimum properties, and heat-treated properties can exceed mild steel. Notable alloys are 2024, the most widely used alloy in aircraft, and 2117, which is used in solid rivets.Some of these alloys are considered non-weldable by the arc welding processes because of their susceptibility to hot cracking and stress corrosion cracking; however, others are arc welded very successfully with the correct welding procedures. These base materials are often welded with high strength 2xxx series filler alloys designed to match their performance, but can sometimes be welded with the 4xxx series fillers containing silicon or silicon and copper, dependent on the application and service requirements.

3000 Series

The 3000 series is best for non-structural uses. 3003 is a notable alloy for being easy to weld. They are of moderate strength, have good corrosion resistance, good formability and are suited for use at elevated temperatures.

3003

3003 is 20% stronger than the 1000 series but is about as workable as pure aluminum. It can be TIG or gas welded, and is non-heat treatable. 3003-H14 is malleable and weldable.

4000 Series

This series of alloys is predominantly found as filler material.Silicon, when added to aluminum, reduces its melting point and improves its fluidity when molten. These characteristics are desirable for filler materials used for both fusion welding and brazing.

5000 Series

5000 series alloys are used for tanks and fluid lines, and are moderate- to high-strength and non heat-treatable. Theyhave the highest strength of the non-heat treatable alloys. In addition, this alloy series is readily weldable, and for these reasons they are used for a wide variety of applications such as shipbuilding, transportation, pressure vessels, bridges and buildings. The magnesium base alloys are often welded with filler alloys, which are selected after consideration of the magnesium content of the base material, and the application and service conditions of the welded component.

Alloys in this series with more than 3.0% magnesium are not recommended for elevated temperature service above 150 deg F because of their potential for sensitization and subsequent susceptibility to stress corrosion cracking. Base alloys with less than approximately 2.5% magnesium are often welded successfully with the 5xxx or 4xxx series filler alloys. The base alloy 5052 is generally recognized as the maximum magnesium content base alloy that can be welded with a 4xxx series filler alloy. Because of problems associated with eutectic melting and associated poor as-welded mechanical properties, it is not recommended to weld material in this alloy series, which contain higher amounts of magnesium with the 4xxx series fillers. The higher magnesium base materials are only welded with 5xxx filler alloys, which generally match the base alloy composition.

6000 Series

The 6000 series has medium strength and good formability and corrosion resistance. A notable alloy is 6061.

6061-T6

High strength but somewhat brittle, hard to weld and may create stress cracks at the weld.

7000 Series

The 7000 series can be high-strength, with a notable alloy being 7075.These are the aluminum / zinc alloys (zinc additions ranging from 0.8 to 12.0%) and comprise some of the highest strength aluminum alloys. These alloys are often used in high performance applications such as aircraft, aerospace, and competitive sporting equipment. Like the 2xxx series of alloys, this series incorporates alloys which are considered unsuitable candidates for arc welding, and others, which are often arc welded successfully.

7075-T6

7075 is one of the strongest aluminum alloys and is frequently used in aerospace and automotive applications where both strength and weight are critical. The largest downside is that welding 7075 is not weldable.