Application, Alloy and Temper Designation
Magnesium and magnesium alloys are used in a wide variety of structural applications include automotive, industrial, materials-handling, commercial and aerospace equipment.
The automotive applications include clutch and brake pedal support brackets, steering column lock housings, and manual transmissions housings. In industrial machinery magnesium alloys are used for parts that operate at high speeds and thus must be lightweight to minimize inertial forces. Commercial applications include hand-held tools, luggage, computer housings, and ladders. Magnesium alloys are valuable for aerospace applications because they are lightweight and exhibit good strength and stiffness at both room and elevated temperatures.
Magnesium is also applied in various nonstructural applications. It is used as an alloying element in alloys of aluminium, zinc, lead, and other nonferrous metals. It is used as an oxygen scavenger and desulfurizer in the manufacture of nickel and copper alloys, as a desulfurizer in the iron and steel industry; and as a reducing agent in the production of beryllium and titanium. Gray iron foundries use magnesium and magnesium-containing alloys as ladle addition agents introduced just before the casting is poured. Magnesium is also being used in pyrotechnics.
Designation for alloys shall consists of not more than two letters representing the alloying elements specified in the greatest amount, arranged in order of decreasing percentages, or in alphabetical order if equal percentages, followed by the respective percentages rounded off to whole numbers and a serial letter. The full name of the base metals precedes the designation, but it is omitted for brevity when the base metal being referred to is obvious.
A standard system of alloy and temper designations, according to ASTM B 275, is explained in the table bellow.
||Fourth part |
|Indicates the two principal alloying elements
||Indicates the amounts of the two principal alloying elements
||Distinguishes between different alloys with the same percentages of the two principal alloying elements
||Indicates condition (temper) |
|Consists of two code letters representing the two main alloying elements arranged in order of decreasing percentage (or alphabetically if percentages are equal)
||Consists of two numbers corresponding to rounded-off percentages of the two main alloying elements and arranged in same order as alloy designations in first part
||Consists of a letter of the alphabet assigned in order as compositions become standard
||Consists of a letter followed by a number (separated from the third part of the designation by a hyphen) |
||Letters of alphabet except I and O
H10 and H11- slightly strain hardened
H23,H24 and H26- strain hardened and partially annealed
T4-solution heat treated
T5-artificially aged only
T6-solution heat treated and artificially aged
T8-solution heat treated, cold worked and artificially aged
As an example of this designation system, consider magnesium alloy AZ81A-T4.
The first part of the designation, AZ, signifies that aluminium and zinc are the two principal alloying elements.
The second part of the designation, 81, gives the rounded-off percentages of aluminium and zinc (8 and 1, respectively).
The third part, A, indicates that it is the fifth alloy standardized with 8% Al and 1% Zn as the principal alloying additions.
The fourth part, T4, denotes that the alloy is solution heat-treated.