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 ALLOY 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

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."

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.

3000 Series

The 3000 series is best for non-structural uses. 3003 is a notable alloy for being easy to weld.

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. (<a href="https://www.oldcarsweekly.com/restoration/metalworking-101-fundamentals-of-fabrication">https://www.oldcarsweekly.com/restoration/metalworking-101-fundamentals-of-fabrication</a>)

5000 Series

5000 series alloys are used for tanks and fluid lines, and are moderate- to high-strength nonheat-treatable.

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.

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.