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.
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First part
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Second part
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Third part
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Fourth part
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Indicates the two principal alloying elements
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Indicates the amounts of the two principal alloying elements
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Distinguishes between different alloys with the same percentages of the two principal alloying elements
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Indicates condition (temper)
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Consists of two code letters representing the two main alloying elements arranged in order of decreasing percentage (or alphabetically if percentages are equal)
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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
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Consists of a letter of the alphabet assigned in order as compositions become standard
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Consists of a letter followed by a number (separated from the third part of the designation by a hyphen)
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A - aluminum
B - bismuth
C - copper
D - cadmium
E - rare earth
F - iron
G - magnesium
H - thorium
K - zirconium
L - lithium
M - manganese
N - nickel
P - lead
Q - silver
R - chromium
S - silicon
T - tin
W - yttrium
Y - antimony
Z - zinc
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Whole numbers
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Letters of alphabet except I and O
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F - as fabricated
O - as annealed
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
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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.
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