Types of Metals | Aluminum
09/09/09 01:45 Filed in: Joyería
Aluminium
From Wikipedia, the free encyclopedia
From Wikipedia, the free encyclopedia
Aluminium (IPA: /����lj����m��ni��m/, /����lj����m��ni��m/) or aluminum (IPA: /����lu��m��n��m/, see the "spelling" section below) is a silvery and ductile member of the poor metal group of chemical elements. It has the symbol Al and atomic number 13.
Aluminium is found primarily in bauxite ore and is remarkable for its ability to resist corrosion (due to the phenomenon of passivation) and its light weight. The metal is used in many industries to manufacture a large variety of products and is very important to the world economy. Structural components made from aluminium and its alloys are vital to the aerospace industry and very important in other areas of transportation and building.
Properties
Aluminium is a soft, lightweight metal normally with a dull gray appearance caused by a thin layer of oxidation that forms quickly when the metal is exposed to air. Aluminium oxide has a higher melting point than pure aluminium. Aluminium is nontoxic (as the metal), nonmagnetic, and nonsparking. It has a tensile strength of about 49 megapascals (MPa) in a pure state and 400 MPa as an alloy. Aluminium is about one-third as dense as steel or copper; it is malleable, ductile, and easily machined and cast. It has excellent corrosion resistance and durability because of the protective oxide layer.
Aluminium is one of the few metals which retain full silvery reflectance, even in finely powdered form, which makes it a very important component of silver paints.
Aluminium's crystal structure is an FCC structure, hence the high ductility of the pure metal.
Aluminium mirror finish has the highest reflectance of any metal in the 200���400 nm (UV) and the 3000���10000 nm (far IR) regions, while in the 400���700 nm visible range it is slightly outdone by silver and in the 700���3000 (near IR) by silver, gold, and copper. It is the second-most malleable metal (after gold) and the sixth-most ductile. Aluminium is a good thermal and electrical conductor, by weight better than copper. Aluminium is capable of being a superconductor, with a superconducting critical temperature of 1.2 Kelvin.
Applications
The statue known as Eros in Piccadilly Circus London, was made in 1893 and is one of the first statues to be cast in aluminium.
General use
Whether measured in terms of quantity or value, the global use of aluminium exceeds that of any other metal except iron, and it is important in virtually all segments of the world economy.
Relatively pure aluminium is encountered only when corrosion resistance and/or workability is more important than strength or hardness. Pure aluminium serves as an excellent reflector (approximately 99%) of visible light and a good reflector (approximately 95%) of infrared. A thin layer of aluminium can be deposited onto a flat surface by chemical vapour deposition or chemical means to form optical coatings and mirrors. These coatings form an even thinner layer of protective aluminium oxide that does not deteriorate, as silver coatings do. Nearly all modern mirrors are made using a thin coating of aluminium on the back surface of a sheet of float glass. Telescope mirrors are also made with aluminium, but are front coated to avoid internal reflections, refraction, and transparency losses. These first surface mirrors are more susceptible to damage than household back-surface mirrors.
Pure aluminium has a low tensile strength, but when combined with thermo-mechanical processing, aluminium alloys display a marked improvement in mechanical properties, especially when tempered. Aluminium alloys form vital components of aircraft and rockets as a result of their high strength-to-weight ratio. Aluminium readily forms alloys with many elements such as copper, zinc, magnesium, manganese and silicon (e.g., duralumin). Today, almost all bulk metal materials that are referred to loosely as "aluminium," are actually alloys. For example, the common aluminium foils are alloys of 92% to 99% aluminium.[1]
Some of the many uses for aluminium metal are in:
* Transportation (automobiles, aircraft, trucks, railroad cars, marine vessels, bicycles etc.)
* Packaging (cans, foil, etc.)
* Water treatment
* Treatment against fish parasites such as Gyrodactylus salaris.
* Construction (windows, doors, siding, building wire, etc.)
* Cooking utensils
* Electrical transmission lines for power distribution
* MKM steel and Alnico magnets
* Super purity aluminium (SPA, 99.980% to 99.999% Al), used in electronics and CDs.
* Heat sinks for electronic appliances such as transistors and CPUs.
* Powdered aluminium is used in paint, and in pyrotechnics such as solid rocket fuels and thermite.
* In the blades of prop swords and knives used in stage combat.
Aluminium Compounds
* Aluminium ammonium sulfate ([Al(NH4)](SO4)2) is used: as a mordant, in water purification and sewage treatment, in paper production, as a food additive, and in leather tanning.
* Aluminium acetate is a salt used in solution as an astringent.
* Aluminium borate (Al2O3 B2O3) is used in the production of glass and ceramic.
* Aluminium borohydride (Al(BH4)3) is used as an additive to jet fuels.
* Aluminium chloride (AlCl3) is used: in paint manufacturing, in antiperspirants, in petroleum refining and in the production of synthetic rubber.
* Aluminium chlorohydride is used as an antiperspirant and as an anhidrotic in the treatment of hyperhidrosis.
* Aluminium fluorosilicate (Al2(SiF6)3) is used in the production of synthetic gemstones, glass and ceramic.
* Aluminium hydroxide (Al(OH)3) is used: as an antacid, as a mordant, in water purification, in the manufacture of glass and ceramic and in the waterproofing of fabrics.
* Aluminium oxide (Al2O3, alumina, is found naturally as corundum (rubies and sapphires), emery, and is used in glass making. Synthetic ruby and sapphire are used in lasers for the production of coherent light.
* Aluminium phosphate (AlPO4) is used in the manufacture: of glass and ceramic, pulp and paper products, cosmetics, paints and varnishes and in making dental cement.
* Aluminium sulphate (Al2(SO4)3) is used: in the manufacture of paper, as a mordant, in a fire extinguisher, in water purification and sewage treatment, as a food additive, in fireproofing, and in leather tanning.
* In many vaccines, certain aluminium salts serve as an immune adjuvant (immune response booster) to allow the protein in the vaccine to achieve sufficient potency as an immune stimulant.
Engineering use
Aluminium alloys with a wide range of properties are used in engineering structures. Alloy systems are classified by a number system (ANSI) or by names indicating their main alloying constituents (DIN and ISO). For more, see the main article referenced.
Aluminium is used extensively in many places due to its high strength to weight ratio. However, a designer used to working with steel will find aluminium less well-behaved in terms of flexibility. The problems may often be addressed by redesigning parts dimensionally specifically to address issues of stiffness. For instance by increasing the second moment of area for a pipe or I-beam, an aluminium design can be made both stiffer and lighter than a traditional design.
The strength and durability of aluminium alloys varies widely, not only as a result of the components of the specific alloy, but also as a result of heat treatments and manufacturing processes. A lack of knowledge of these aspects has from time to time led to improperly designed structures and gained aluminium a bad reputation. (See main article)
One important structural limitation of aluminium alloys is their fatigue strength. Unlike steels, aluminium alloys have no well defined fatigue limit, meaning that fatigue failure will eventually occur under even very small cyclic loadings. This implies that engineers must assess these loads and design for a fixed life rather than an infinite life.
Another important property of aluminium alloys is their sensitivity to heat. Workshop procedures involving heating are complicated by the fact that aluminium, unlike steel, will melt without first glowing red. Forming operations where a blow torch is used therefore requires some expertise, since no visual signs reveal how close the material is to melting. Aluminium alloys, like all structural alloys, also are subject to internal stresses following heating operations such as welding and casting. The problem with aluminium alloys in this regard is their low melting point, which make them more susceptible to distortions from thermally induced stress relief. Controlled stress relief can be done during manufacturing by heat-treating the parts in an oven, followed by gradual cooling - in effect annealing the stresses.
The low melting point of aluminium alloys has not precluded their use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region; in fact the extremely high thermal conductivity of aluminium prevented the throat from reaching the melting point even under massive heat flux, resulting in a reliable and lightweight component.
Household wiring
Aluminium has about 65% of the conductivity of copper, the traditional household wiring material. In the 1960s aluminium was considerably cheaper than copper, and so was introduced for household electrical wiring in the United States, even though many fixtures had not been designed to accept aluminium wire. However, in some cases the greater coefficient of thermal expansion of aluminium causes the wire to expand and contract relative to the dissimilar metal screw connection, eventually loosening the connection. Also, pure aluminium has a tendency to "creep" under steady sustained pressure (to a greater degree as the temperature rises), again loosening the connection. Finally, Galvanic corrosion from the dissimilar metals increased the electrical resistance of the connection.
All of this resulted in overheated and loose connections, and this in turn resulted in some fires. Builders then became wary of using the wire, and many jurisdictions outlawed its use in very small sizes, in new construction. Eventually, newer fixtures were introduced with connections designed to avoid loosening and overheating. At first they were marked "Al/Cu", but they now bear a "CO/ALR" coding. In older assemblies, workers forestall the heating problem using a properly-done crimp of the aluminium wire to a short "pigtail" of copper wire. Today, new alloys, designs, and methods are used for aluminium wiring in combination with aluminium terminations.
History
Ancient Greeks and Romans used aluminium salts as dyeing mordants and as astringents for dressing wounds; alum is still used as a styptic. In 1761 Guyton de Morveau suggested calling the base alum alumine. In 1808, Humphry Davy identified the existence of a metal base of alum, which he at first named alumium and later aluminum (see Spelling section, below).
Friedrich W̦hler is generally credited with isolating aluminium (Latin alumen, alum) in 1827 by mixing anhydrous aluminium chloride with potassium. The metal, however, had indeed been produced for the first time two years earlier ��� but in an impure form ��� by the Danish physicist and chemist Hans Christian ��rsted. Therefore, ��rsted can also be listed as the discoverer of the metal.[2] Further, Pierre Berthier discovered aluminium in bauxite ore and successfully extracted it. [3] The Frenchman Henri Etienne Sainte-Claire Deville improved W̦hler's method in 1846 and described his improvements in a book in 1859, chief among these being the substitution of sodium for the considerably more expensive potassium.
(Note: The title of Deville's book is "De l'aluminium, ses propri̩t̩s, sa fabrication" (Paris, 1859). It was quite likely that Deville also thought of the idea of the electrolysis of aluminum oxide dissolved in cryolite. However, Charles Martin Hall and Paul Heroult might have developed the more practical process after Deville.)
The statue known as Eros in Piccadilly Circus London, was made in 1893 and is one of the first statues to be cast in aluminium.
The statue known as Eros in Piccadilly Circus London, was made in 1893 and is one of the first statues to be cast in aluminium.
Aluminium was selected as the material to be used for the apex of the Washington Monument, at a time when one ounce (30 grams) cost twice the daily wages of a common worker in the project; aluminium was a semiprecious metal at that time.[4]
The American Charles Martin Hall of Oberlin, Ohio applied for a patent (U.S. Patent 400,664 ) in 1886 for an electrolytic process to extract aluminium using the same technique that was independently being developed by the Frenchman Paul H̩roult in Europe. The invention of the Hall-H̩roult process in 1886 made extracting aluminium from minerals cheaper, and is now the principal method in common use throughout the world. The Hall-Heroult process cannot produce Super Purity Aluminium directly. Upon approval of his patent in 1889, Hall, with the financial backing of Alfred E. Hunt of Pittsburgh, PA, started the Pittsburgh Reduction Company, renamed to Aluminum Company of America in 1907, later shortened to Alcoa. Germany became the world leader in aluminium production soon after Adolf Hitler's rise to power. By 1942, however, new hydroelectric power projects such as the Grand Coulee Dam gave the United States something Nazi Germany could not compete with, provided them with sufficient generating capacity to produce enough aluminium to manufacture sixty thousand warplanes in four years.[5]
Aluminium is found primarily in bauxite ore and is remarkable for its ability to resist corrosion (due to the phenomenon of passivation) and its light weight. The metal is used in many industries to manufacture a large variety of products and is very important to the world economy. Structural components made from aluminium and its alloys are vital to the aerospace industry and very important in other areas of transportation and building.
Properties
Aluminium is a soft, lightweight metal normally with a dull gray appearance caused by a thin layer of oxidation that forms quickly when the metal is exposed to air. Aluminium oxide has a higher melting point than pure aluminium. Aluminium is nontoxic (as the metal), nonmagnetic, and nonsparking. It has a tensile strength of about 49 megapascals (MPa) in a pure state and 400 MPa as an alloy. Aluminium is about one-third as dense as steel or copper; it is malleable, ductile, and easily machined and cast. It has excellent corrosion resistance and durability because of the protective oxide layer.
Aluminium is one of the few metals which retain full silvery reflectance, even in finely powdered form, which makes it a very important component of silver paints.
Aluminium's crystal structure is an FCC structure, hence the high ductility of the pure metal.
Aluminium mirror finish has the highest reflectance of any metal in the 200���400 nm (UV) and the 3000���10000 nm (far IR) regions, while in the 400���700 nm visible range it is slightly outdone by silver and in the 700���3000 (near IR) by silver, gold, and copper. It is the second-most malleable metal (after gold) and the sixth-most ductile. Aluminium is a good thermal and electrical conductor, by weight better than copper. Aluminium is capable of being a superconductor, with a superconducting critical temperature of 1.2 Kelvin.
Applications
The statue known as Eros in Piccadilly Circus London, was made in 1893 and is one of the first statues to be cast in aluminium.
General use
Whether measured in terms of quantity or value, the global use of aluminium exceeds that of any other metal except iron, and it is important in virtually all segments of the world economy.
Relatively pure aluminium is encountered only when corrosion resistance and/or workability is more important than strength or hardness. Pure aluminium serves as an excellent reflector (approximately 99%) of visible light and a good reflector (approximately 95%) of infrared. A thin layer of aluminium can be deposited onto a flat surface by chemical vapour deposition or chemical means to form optical coatings and mirrors. These coatings form an even thinner layer of protective aluminium oxide that does not deteriorate, as silver coatings do. Nearly all modern mirrors are made using a thin coating of aluminium on the back surface of a sheet of float glass. Telescope mirrors are also made with aluminium, but are front coated to avoid internal reflections, refraction, and transparency losses. These first surface mirrors are more susceptible to damage than household back-surface mirrors.
Pure aluminium has a low tensile strength, but when combined with thermo-mechanical processing, aluminium alloys display a marked improvement in mechanical properties, especially when tempered. Aluminium alloys form vital components of aircraft and rockets as a result of their high strength-to-weight ratio. Aluminium readily forms alloys with many elements such as copper, zinc, magnesium, manganese and silicon (e.g., duralumin). Today, almost all bulk metal materials that are referred to loosely as "aluminium," are actually alloys. For example, the common aluminium foils are alloys of 92% to 99% aluminium.[1]
Some of the many uses for aluminium metal are in:
* Transportation (automobiles, aircraft, trucks, railroad cars, marine vessels, bicycles etc.)
* Packaging (cans, foil, etc.)
* Water treatment
* Treatment against fish parasites such as Gyrodactylus salaris.
* Construction (windows, doors, siding, building wire, etc.)
* Cooking utensils
* Electrical transmission lines for power distribution
* MKM steel and Alnico magnets
* Super purity aluminium (SPA, 99.980% to 99.999% Al), used in electronics and CDs.
* Heat sinks for electronic appliances such as transistors and CPUs.
* Powdered aluminium is used in paint, and in pyrotechnics such as solid rocket fuels and thermite.
* In the blades of prop swords and knives used in stage combat.
Aluminium Compounds
* Aluminium ammonium sulfate ([Al(NH4)](SO4)2) is used: as a mordant, in water purification and sewage treatment, in paper production, as a food additive, and in leather tanning.
* Aluminium acetate is a salt used in solution as an astringent.
* Aluminium borate (Al2O3 B2O3) is used in the production of glass and ceramic.
* Aluminium borohydride (Al(BH4)3) is used as an additive to jet fuels.
* Aluminium chloride (AlCl3) is used: in paint manufacturing, in antiperspirants, in petroleum refining and in the production of synthetic rubber.
* Aluminium chlorohydride is used as an antiperspirant and as an anhidrotic in the treatment of hyperhidrosis.
* Aluminium fluorosilicate (Al2(SiF6)3) is used in the production of synthetic gemstones, glass and ceramic.
* Aluminium hydroxide (Al(OH)3) is used: as an antacid, as a mordant, in water purification, in the manufacture of glass and ceramic and in the waterproofing of fabrics.
* Aluminium oxide (Al2O3, alumina, is found naturally as corundum (rubies and sapphires), emery, and is used in glass making. Synthetic ruby and sapphire are used in lasers for the production of coherent light.
* Aluminium phosphate (AlPO4) is used in the manufacture: of glass and ceramic, pulp and paper products, cosmetics, paints and varnishes and in making dental cement.
* Aluminium sulphate (Al2(SO4)3) is used: in the manufacture of paper, as a mordant, in a fire extinguisher, in water purification and sewage treatment, as a food additive, in fireproofing, and in leather tanning.
* In many vaccines, certain aluminium salts serve as an immune adjuvant (immune response booster) to allow the protein in the vaccine to achieve sufficient potency as an immune stimulant.
Engineering use
Aluminium alloys with a wide range of properties are used in engineering structures. Alloy systems are classified by a number system (ANSI) or by names indicating their main alloying constituents (DIN and ISO). For more, see the main article referenced.
Aluminium is used extensively in many places due to its high strength to weight ratio. However, a designer used to working with steel will find aluminium less well-behaved in terms of flexibility. The problems may often be addressed by redesigning parts dimensionally specifically to address issues of stiffness. For instance by increasing the second moment of area for a pipe or I-beam, an aluminium design can be made both stiffer and lighter than a traditional design.
The strength and durability of aluminium alloys varies widely, not only as a result of the components of the specific alloy, but also as a result of heat treatments and manufacturing processes. A lack of knowledge of these aspects has from time to time led to improperly designed structures and gained aluminium a bad reputation. (See main article)
One important structural limitation of aluminium alloys is their fatigue strength. Unlike steels, aluminium alloys have no well defined fatigue limit, meaning that fatigue failure will eventually occur under even very small cyclic loadings. This implies that engineers must assess these loads and design for a fixed life rather than an infinite life.
Another important property of aluminium alloys is their sensitivity to heat. Workshop procedures involving heating are complicated by the fact that aluminium, unlike steel, will melt without first glowing red. Forming operations where a blow torch is used therefore requires some expertise, since no visual signs reveal how close the material is to melting. Aluminium alloys, like all structural alloys, also are subject to internal stresses following heating operations such as welding and casting. The problem with aluminium alloys in this regard is their low melting point, which make them more susceptible to distortions from thermally induced stress relief. Controlled stress relief can be done during manufacturing by heat-treating the parts in an oven, followed by gradual cooling - in effect annealing the stresses.
The low melting point of aluminium alloys has not precluded their use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region; in fact the extremely high thermal conductivity of aluminium prevented the throat from reaching the melting point even under massive heat flux, resulting in a reliable and lightweight component.
Household wiring
Aluminium has about 65% of the conductivity of copper, the traditional household wiring material. In the 1960s aluminium was considerably cheaper than copper, and so was introduced for household electrical wiring in the United States, even though many fixtures had not been designed to accept aluminium wire. However, in some cases the greater coefficient of thermal expansion of aluminium causes the wire to expand and contract relative to the dissimilar metal screw connection, eventually loosening the connection. Also, pure aluminium has a tendency to "creep" under steady sustained pressure (to a greater degree as the temperature rises), again loosening the connection. Finally, Galvanic corrosion from the dissimilar metals increased the electrical resistance of the connection.
All of this resulted in overheated and loose connections, and this in turn resulted in some fires. Builders then became wary of using the wire, and many jurisdictions outlawed its use in very small sizes, in new construction. Eventually, newer fixtures were introduced with connections designed to avoid loosening and overheating. At first they were marked "Al/Cu", but they now bear a "CO/ALR" coding. In older assemblies, workers forestall the heating problem using a properly-done crimp of the aluminium wire to a short "pigtail" of copper wire. Today, new alloys, designs, and methods are used for aluminium wiring in combination with aluminium terminations.
History
Ancient Greeks and Romans used aluminium salts as dyeing mordants and as astringents for dressing wounds; alum is still used as a styptic. In 1761 Guyton de Morveau suggested calling the base alum alumine. In 1808, Humphry Davy identified the existence of a metal base of alum, which he at first named alumium and later aluminum (see Spelling section, below).
Friedrich W̦hler is generally credited with isolating aluminium (Latin alumen, alum) in 1827 by mixing anhydrous aluminium chloride with potassium. The metal, however, had indeed been produced for the first time two years earlier ��� but in an impure form ��� by the Danish physicist and chemist Hans Christian ��rsted. Therefore, ��rsted can also be listed as the discoverer of the metal.[2] Further, Pierre Berthier discovered aluminium in bauxite ore and successfully extracted it. [3] The Frenchman Henri Etienne Sainte-Claire Deville improved W̦hler's method in 1846 and described his improvements in a book in 1859, chief among these being the substitution of sodium for the considerably more expensive potassium.
(Note: The title of Deville's book is "De l'aluminium, ses propri̩t̩s, sa fabrication" (Paris, 1859). It was quite likely that Deville also thought of the idea of the electrolysis of aluminum oxide dissolved in cryolite. However, Charles Martin Hall and Paul Heroult might have developed the more practical process after Deville.)
The statue known as Eros in Piccadilly Circus London, was made in 1893 and is one of the first statues to be cast in aluminium.
The statue known as Eros in Piccadilly Circus London, was made in 1893 and is one of the first statues to be cast in aluminium.
Aluminium was selected as the material to be used for the apex of the Washington Monument, at a time when one ounce (30 grams) cost twice the daily wages of a common worker in the project; aluminium was a semiprecious metal at that time.[4]
The American Charles Martin Hall of Oberlin, Ohio applied for a patent (U.S. Patent 400,664 ) in 1886 for an electrolytic process to extract aluminium using the same technique that was independently being developed by the Frenchman Paul H̩roult in Europe. The invention of the Hall-H̩roult process in 1886 made extracting aluminium from minerals cheaper, and is now the principal method in common use throughout the world. The Hall-Heroult process cannot produce Super Purity Aluminium directly. Upon approval of his patent in 1889, Hall, with the financial backing of Alfred E. Hunt of Pittsburgh, PA, started the Pittsburgh Reduction Company, renamed to Aluminum Company of America in 1907, later shortened to Alcoa. Germany became the world leader in aluminium production soon after Adolf Hitler's rise to power. By 1942, however, new hydroelectric power projects such as the Grand Coulee Dam gave the United States something Nazi Germany could not compete with, provided them with sufficient generating capacity to produce enough aluminium to manufacture sixty thousand warplanes in four years.[5]