INFORMATION ABOUT ALUMINUM ALLOYS
(this is just as much for my own personal edification as well as anyone who is interested)
Strength is increased by the addition of magnesium (up to about 7% by weight) and also additions of zinc, copper, and/or silicon in conjunction with Mg.
High temp strength is achieved by adding up to 4wt% Cu and/or nickel, manganese, or iron (none of these latter elements are added above 1wt% - they are heavy alloying elements as well).
Chemical and Corrosion resistance is obtained with the addition of Mg, Mn, or a combination of Mg and Si.
Machinability is greatly improved by the addition of lead and bismuth up to 0.6 wt% each.
Grain refinement (which often leads to better strength in castings) is obtained via the addition of titanium and boron in very small amounts. Solid Ti and borides in the melt pool provide a greater nucleation site density during solidification, thus creating more nucleation sites per unit volume, thus reducing grain size. Chromium and zirconium (up to 0.1wt%) will also refine grains, along with iron and manganese.
Homogeneity in casting is achieved by adding up to 13 wt% of Si. Dimensional stability at high temperature is achieved by adding as much as 25 wt% Si, leading to a fiber reinforced metal composite. This is often used in the fabrication of aluminum PISTONS.
Major Alloying Elements and Aluminum Series Designation for Wrought Alloys
1xxx >99% Al
6xxx Mg and Si
9xxx Unused as of now
Four digits are used to identify wrought aluminum and its alloys. The alloy group is identified by the first digit. Modifications of the original alloy and impurity limits are indicated by the second digit. In the case of the 1xxx group, the last two digits indicate the minimum aluminum percentage. For the 2xxx through 8xxx groups, the last two digits serve to further identify individual aluminum alloys. For experimental alloys, a prefix capital "X" is added, i.e., X2037.
CastingsFor castings, a different standard is used, i.e., xxx.x.
1xx.x 99% Aluminum or more
3xx.x Si + Cu or Mg
Wrought Alloy Designations
1xxx - Pure Al
Ex. 1100 (99% pure Al), 1050 (99.5% pure), 1350 (99.5%), 1175 (99.75%).
Some used for electrical applications, like 1350. Not ideal for strength. Better for corrosion resistance, high formability, and conductivity.
2xxx - Al-Cu Alloys
Ex. 2014, 2024, 2219.
Heat treatable alloys, good for strength, especially at high temps. Good toughness (i.e., good for fracture-critical applications). Good weldability. Usually painted to improve corrosion resistance, as it isn't all that great otherwise. 2024 is used in aircraft, 2014 is used in automotive body applications - bolted or riveted. 2219 and 2048 show good weldability and are thus ideal for aerospace. 2195 includes lithium as an alloying element, shows good strength and weldability, and also sees usage in aerospace. 2124 and 2149 have good fracture toughness and are used in aircraft. 2011, 2017, and 2117 are widely used for fasteners and screw-machine stock.
3xxx - Al-Si alloys
Ex. 3003, 3004, 3105.
Strain hardenable alloys have excellent corrosion resistance, reasonable weldability, brazability, and solderability. Alloys 3004 and 3104 are widely known and used (out of all Al alloys) because they are used in beverage cans. 3003 is used in cooking utensils, chemical equipment, and builder's hardware. 3105 is used in roofing and siding. A lot of the 3xxx series is used in sheet and tubular form.
4xxx - Al-Mg alloys
Ex. 4032, 4043.
4032 is medium to high strength and heat treatable used principally for forgings. 4043, on the other hand, is widely used as a filler for GMA welding 6xxx alloys. 4043 is also used in structural and automotive applications. High Si content leads to better molten flow in molds and during welding. Also used for cladding and brazing.
5xxx - Al-Mg Alloys
Ex. 5052, 5083, 5086, 5183, 5754.
Strain hardenable, moderately high strength, excellent corrosion resistance (even in salt water), high toughness even at cryogenic temps. Readily welded and therefore find a wide range of applications in construction of bridges, storage tanks, pressure vessels, cryogenic tank systems, and marine applications. 5052, 5086, 5083 are work horses for structural applications, and strength increases with increasing Mg content. 5182 is used in beverage can end caps, 5754 is used in automotive bodies and frames, 5252, 5457, and 5657 are used for bright automotive trim applications (very polishable).
6xxx - Al-Mg-Si Alloys
Ex. 6061, 6063, 6111.
Heat treatable, moderately high strength, excellent corrosion resistance. Readily welded. Exturdable as well! First choice for architectural and structural members where unusual strength or stiffness (high modulus) is required. Alloy 6063 is widely used in aluminum bridge structures and automotive space frames. 6061 has better strength than 6063, and is used in truck and marine frames, railroad cars, and pipelines. 6066-T6 is used in high strength forgings, 6111 is used in automotive panels with high dent resistance, and 6201 is used in high strength conductive wire.
7xxx - Al-Zn Alloys
Ex. 7005, 7050, 7075, 7475.
Heat treatable and provide highest strengths of all aluminum alloys. 7150 and 7475 have controlled impurity levels to maximize the combination of strength and fracture toughness. The aircraft industry uses a lot of 7-series alloys, though they are not generally very weldable. Usually they are used in riveted construction. Corrosion resistance is not as high as 5xxx or 6xxx alloys, so 7xxx alloys are usually coated.
8xxx - Al + other elements
Ex. 8017, 8090.
Use alloying elements such as Fe, Ni, and Li. Fe and Ni provide strength with little loss in conductivity such as in the 8017 alloy (which is used in conductive applications). Li provides a high modulus in aerospace applications.
Source: Aluminum: Technology, Applications, and Environment. A Profile of a Modern Metal. 6th Ed. Dietrich G. Altenpohl. The Minerals, Metals, and Materials Society (TMS). 1998. ISBN #: 0-87339-406-2
F -- As Fabricated - No special control has been performed to the heat treatment or strain hardening after the shaping process such as casting, hot working, or cold working.
O -- Annealed - This is the lowest strength, highest ductility temper
H -- Strain Hardened - (applied to wrought products only) Used for products that have been strengthened by strain hardening, with or without subsequent heat treatment. The designation is followed by two or more numbers as discussed below.
W -- Solution Heat Treated - This is seldom encountered because it is an unstable temper that applies only to alloys that spontaneously age at ambient temperature after heat treatment.
T -- Solution Heat Treated - Used for products that have been strengthened by heat treatment, with or without subsequent strain hardening. The designation is followed by one or more numbers as discussed below.
T Temper Codes
T1 - Cooled from an elevated temperature shaping process and naturally aged to a substantially stable condition.
T2 - Cooled from an elevated temperature shaping process, cold worked, and naturally aged to a substantially stable condition.
T3 - Solution heat treated, cold worked, and naturally aged to a substantially stable condition.
T4 - Solution heat treated, and naturally aged to a substantially stable condition.
T5 - Cooled from an elevated temperature shaping process then artificially aged.
T6 - Solution heat treated then artificially aged.
T7 - Solution heat treated then and overaged/stabilized.
T8 - Solution heat treated, cold worked, then artificially aged.
T9 - Solution heat treated, artificially aged, then cold worked.
T10 - Cooled from an elevated temperature shaping process, cold worked, then artificially aged.
Additional digits may be used after the first T temper digit to indicate subsequent stress relieving by processes such as stretching, compressing, or a combination of the two.
H Temper Strain Hardening Codes
H1 - Strain hardened only
H2 - Strain hardened and partially annealed
H3 - Strain hardened and stabilized
H4 - Strain hardened and lacquered or painted. This assumes that thermal affects from the coating process affect the strain hardening; not encountered often.
The second digits (required) after the first H temper digit indicates the level of strain hardening and is based on the minimum ultimate tensile strength obtained. The third digit (optional) is a variation of the two digit temper.
Also, see http://www.matweb.com/referenc...r.asp
Modified by DHill at 10:43 AM 5-16-2007
Modified by DHill at 10:45 AM 5-16-2007