Metallurgy for Dummies

The Metallurgy's Blog for Beginners 
What are Alloys?

What is Alloy?

An alloy is a metal composed of more than one element. Engineering alloys include the cast-irons and steels, aluminum alloys, magnesium alloys, titanium alloys, nickel alloys, zinc alloys and copper alloys. For example, brass is an alloy of copper and zinc. An alloy is a metallic substance that is made from the mixture of multiple metals or, sometimes, a metal with some other element such as carbon. Alloys have been around for about nine millennia, but like most other domains in science and technology, the bulk of progress in alloy technology has occurred in the last few decades. In an alloy, the constituent elements are not meant to combine into larger molecules through chemical reactions, but are merely mixed together. When there are different ratios between two or more metals, the alloys produced have slightly different properties. Alloy is a metal made by combining 2 or more metallic elements, especially to give strength or resistance to corroding.

Alloying a metal is done by combining it with one or more other metals or non-metals that often enhance its properties. For example, steel is stronger than iron, its primary element. The physical properties, such as density, reactivity, Young’s modulus, and electrical and thermal conductivity, of an alloy may not differ greatly from those of its elements, but engineering properties such as tensile strength and shear strength may be substantially different from those of the constituent materials. This is sometimes a result of the sizes of the atoms in the alloy, because larger atoms exert a compressive force on neighboring atoms, and smaller atoms exert a tensile force on their neighbors, helping the alloy resist deformation. Sometimes alloys may exhibit marked differences in behavior even when small amounts of one element occur. For example, impurities in semi-conducting ferromagnetic alloys lead to different properties, as first predicted by White, Hogan, Suhl, Tian Abrie and Nakamura.

Some alloys are made by melting and mixing two or more metals. Bronze, an alloy of copper and tin, was the first alloy discovered, during the prehistoric period now known as the bronze age, it was harder than pure copper and originally used to make tools and weapons, but was later superseded by metals and alloys with better properties. In later times bronze has been used for ornaments, bells, statues, and bearings. Brass is an alloy made from copper and zinc. The first metal to be extracted from ore was copper. Shortly thereafter, it was combined with tin to create the stronger bronze, which dominated human technology for thousands of years.

This period is now called the Bronze Age. alloying is a term which describes a material which, when introduced to another material will change its characteristics to make them advantageous to us. they are split into 2 categories, “Matrix’s” and “reinforcement agent”. For example with carbon fibre the matrix is the carbon and the reinforcement agent is a resin. Other metals mixed with copper to form cruder variants of bronze were manganese, aluminum, silicon, and phosphorous. Co-existing for many years with bronze was the weaker iron, which decays quickly into rust. Eventually, historic forces caused iron to supplant bronze in human tools, ushering in the Iron Age around 1000 BCE, though this date varies depending on the civilization and region being considered.

Alloying a metal is done by combining it with one or more other metals or non-metals that often enhance its properties. For example, steel is stronger than iron, its primary element. Bronze, an alloy of copper and tin, was the first alloy discovered, during the prehistoric period now known as the bronze age, it was harder than pure copper and originally used to make tools and weapons, but was later superseded by metals and alloys with better properties. Brass is an alloy made from copper and zinc. The use of alloys by humans started with the use of meteoric iron, a naturally occurring alloy of nickel and iron. The term alloy is used to describe a mixture of atoms in which the primary constituent is a metal. If there is a mixture of only two types of atoms, not counting impurities, such as a copper-nickel alloy, then it is called a binary alloy. If there are three types of atoms forming the mixture, such as iron, nickel and chromium, then it is called a ternary alloy. An alloy with four constituents is a quaternary alloy, while a five-part alloy is termed a quinary alloy. Pig iron, a very hard but brittle alloy of iron and carbon, was being produced in China as early as 1200 BC, but did not arrive in Europe until the Middle Ages.

These metals found little practical use until the introduction of crucible steel around 300 BC. When a molten metal is mixed with another substance, there are two mechanisms that can cause an alloy to form, called atom exchange and the interstitial mechanism. Examples of substitutional alloys include bronze and brass, in which some of the copper atoms are substituted with either tin or zinc atoms. The smaller atoms become trapped in the spaces between the atoms in the crystal matrix, called the interstices. This is referred to as an interstitial alloy. Steel is an example of an interstitial alloy, because the very small carbon atoms fit into interstices of the iron matrix. Stainless steel is an example of a combination of interstitial and substitutional alloys, because the carbon atoms fit into the interstices, but some of the iron atoms are replaced with nickel and chromium atoms.

Alloys are often made to alter the mechanical properties of the base metal, to induce hardness, toughness, ductility, or other desired properties. While most metals and alloys can be work hardened by inducing defects in their crystal structure, caused by plastic deformation, some alloys can also have their properties altered by heat treatment. At a certain temperature, the base metal of steel, iron, undergoes a change in the arrangement of the atoms in its crystal matrix, called allotropy. This allows the small carbon atoms to enter the interstices of the crystal. For example, 14 karat gold is an alloy of gold with other elements. The term “alloy” is sometimes used in everyday speech as a synonym for a particular alloy. For example, automobile wheels made of an aluminium alloy are commonly referred to as simply “alloy wheels”, although in point of fact steels and most other metals in practical use are also alloys. Mercury dissolves many metals, such as gold, silver, and tin, to form amalgams (an alloy in a soft paste, or liquid form at ambient temperature). Many ancient civilizations alloyed metals for purely aesthetic purposes. In ancient Egypt and Mycenae, gold was often alloyed with copper to produce red-gold, or iron to produce a bright burgundy-gold. Silver was often found alloyed with gold. Because pig iron could be melted, people began to develop processes of reducing the carbon in the liquid pig iron to create steel. The Bessemer process was able to produce the first large scale manufacture of steel. Once the Bessemer process began to gain widespread use, other alloys of steel began to follow, such as mangalloy, an alloy of steel and manganese, which exhibits extreme hardness and toughness.

Zinc Alloys

Zinc Alloys are combinations of zinc with one or more other metals. If zinc is the primary constituent of the alloy, it is a zinc-base alloy. Zinc also is commonly used in varying degrees as an alloying component with other base metals, such as copper, aluminum, and magnesium. A familiar example of the latter is the association of varying amounts of zinc (up to 45%) with copper to produce brass. Zinc, a crystalline metal with moderate strength and ductility, is seldom used alone except as a coating. After iron, aluminium and copper, zinc is usually the fourth-most used metal. There are many wrought alloys with various alloying elements to improve workability and strenght. There are two major Zinc alloy groups for casting. The first is a standard casting alloy that is primarily Zinc in a hypo-eutectic alloy with less than 5% Aluminum. The Second is the newer group of Zinc-Aluminum alloys. These are hyper-eutectic alloys with up to 27% Aluminum. Both groups are primarily used in die casting.

The modern development started during the 80’s with the first alkaline Zn/Fe (99,5%/0,5%) deposits and Zn/Ni (94%/6%) deposits. Recently, the reinforcement of the corrosion specifications of the major European Car Makers and the Directive ELV that banished the use of hexavalent Chromium (CrVI) Conversion Coating required greater use of alkaline Zn/Ni between 12 and 15% of Ni (Zn/Ni 86/14). Only Zn/Ni (86%/14%) is an alloy while lower content of Iron, Cobalt and Nickel leads to co-deposits. Zn/Ni (12%-15%) in Nickel in acidic and alkaline electrolytes is plated as the gamma crystalline phase of the binary diagram Zn-Ni. Wrought zinc and zinc alloys may be obtained as rolled strip, sheet and foil; extruded rod and shapes and drawn rod and wire. These metals exhibit good resistance to corrosion in many types of service, and because the corrosion products that may form on them are white, other materials are not stained by them.

Wrought zinc has chemical characteristics particularly adapted to certain uses, such as dry batteries and photoengraver`s plate, and offers combinations of desirable physical and mechanical properties at relatively low cost. In common with many other metals and alloys, wrought zinc creeps under constant loads that are substantially less than its ultimate strength that is, wrought zinc does not have clearly defined elastic module, and hence creep data from service tests must be used in designing for strength and rigidity under conditions of continuos stress. All severe fabrication of wrought zinc should be done at temperatures above 20°C. Rolled zinc of the proper grade is readily drawn into a great variety of articles such as batter cups, eyelets, meter cases, novelties, flashlight reflectors and fruit-jar caps.

Suitable grades of rolled zinc also are readily rolled, press formed, stamped or spun into items such as plates for addressing machines, buckles, ferrules, ornaments, nameplates, gaskets, weather-stripping and lamp parts. The ordinary grades of wrought zinc can be soldered easily by conventional methods. The usual precautions should be observed regarding proper cleaning and fluxing. The metal must not be overheated to the point where it melts. Pulsed-arc welding may be used for joining; gas welding of zinc is used only for repair work. Wrought zinc is easily machined using standard methods and tools. However, if it is necessary to machine zinc containing exceedingly coarse grains, the metal should be heated to a temperature between 70 and 100°C in order to avoid cleavage of crystals. Wrought zinc has chemical characteristics particularly adapted to certain uses, such as dry batteries and photoengraver`s plate, and offers combinations of desirable physical and mechanical properties at relatively low cost. In common with many other metals and alloys, wrought zinc creeps under constant loads that are substantially less than its ultimate strength. The ordinary grades of wrought zinc can be soldered easily by conventional methods.

Zinc gravity casting alloys can be used for general industrial applications where strength, hardness, wear resistance or good pressure tightness is required. Zinc alloys often are employed to replace cast iron because of their similar properties and higher machinability ratings. The good bearing and wear characteristics of zinc alloys permit them to be used for bearing bushings and flanges. Other applications in which zinc alloys have been successfully substituted for cast iron or copper alloys include fuel-handling components, pulleys, electrical fittings and hardware components.

pure Zinc is never used in casting due to it’s low strength. Today, all Zinc alloys supplied by reputable producers are made from primary of virgin Zinc which conforms to the SHG (super high grade) or Zn 1 brand which is quoted in commodity markets worldwide. The corrosion protection is primarily due to the anodic potential dissolution of zinc versus iron. Zinc is acting as sacrificial anode for protecting iron (steel). While steel is close to -400 mV, depending on alloy composition, electroplated zinc is much more anodic with -980 mV. Steel is preserved from corrosion by cathodic protection. This enhances corrosion protection further. On the opposite Zn/Ni between 12% and 15% of Ni (Zn/Ni 86/14) has a potential around -680 mV closer to Cadmium -640 mV. Thanks to this mechanism of corrosion, this alloy offers much greater protection than all other alloys.

For cost reasons the existing market is dividing between alkaline Zn/Fe (99,5%/0,5%) and alkaline Zn/Ni (86%/14%). The former Zn/Ni (94%/6%) that was a blend between pure zinc and the crystallographic gamma phase of Zn/Ni (86%/14%), was withdrawn from the European specs. A specific advantage of alkaline Zn/Ni (86%/14%) involves the lack of hydrogen embrittlement by plating. This initial layer preventshydrogen from penetrating deep into the steel substrate thus avoiding the serious problems associated with hydrogen embrittlement.

Aluminum Alloys

Aluminium alloys are alloys in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About 85% of aluminium is used for wrought products, for example rolled plate, foils and extrusions. Cast aluminium alloys yield cost effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminium alloy system is Al-Si, where the high levels of silicon (4.0% to 13%) contribute to give good casting characteristics. Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required.

An alloy is a material made up of two or more metals. Alloys have certain specific, desirable characteristics, including strength, formability, and corrosion resistance. Some of the common elements alloyed with aluminum include copper, manganese, silicon, magnesium, and zinc. Typical applications and uses of aluminum alloys include building products (siding and structural), rigid and flexible packaging (foil, food, and beverage cans), and transportation (automobiles, aircraft, and rail cars).

Aluminum is a silverish white metal that has a strong resistance to corrosion and like gold, is rather malleable. It is a relatively light metal compared to metals such as steel, nickel, brass, and copper with a specific gravity of 2.7. Aluminum is easily machinable and can have a wide variety of surface finishes. It also has good electrical and thermal conductivities and is highly reflective to heat and light.

At extremely high temperatures (200-250°C) aluminum alloys tend to lose some of their strength. However, at subzero temperatures, their strength increases while retaining their ductility, making aluminum an extremely useful low-temperature alloy. Aluminum alloys have a strong resistance to corrosion which is a result of an oxide skin that forms as a result of reactions with the atmosphere. This corrosive skin protects aluminum from most chemicals, weathering conditions, and even many acids, however alkaline substances are known to penetrate the protective skin and corrode the metal. Aluminum also has a rather high electrical conductivity, making it useful as a conductor. Copper is the more widely used conductor, having a conductivity of approximately 161% that of aluminum. Aluminum connectors have a tendency to become loosened after repeated usage leading to arcing and fire, which requires extra precaution and special design when using aluminum wiring in buildings.

Aluminum is a very versatile metal and can be cast in any form known. It can be rolled, stamped, drawn, spun, roll-formed, hammered and forged. The metal can be extruded into a variety of shapes, and can be turned, milled, and bored in the machining process. Aluminum can riveted, welded, brazed, or resin bonded. For most applications, aluminum needs no protective coating as it can be finished to look good, however it is often anodized to improve color and strength.

Aluminum Alloys can be divided into nine groups.

1xxx Unalloyed (pure) >99% Al
2xxx Copper is the principal alloying element, though other elements (Magnesium) may be specified
3xxx Manganese is the principal alloying element
4xxxSilicon is the principal alloying element
5xxxMagnesium is the principal alloying element
6xxxMagnesium and Silicon are principal alloying elements
7xxxZinc is the principal alloying element, but other elements such as Copper, Magnesium, Chromium, and Zirconium may be specified
8xxxOther elements (including Tin and some Lithium compositions)
9xxx Reserved for future use


1xxx Series. These grades of aluminum are characterized by excellent corrosion resistance, high thermal and electrical conductivities, low mechanical properties, and excellent workability. Moderate increases in strength may be obtained by strain hardening. Iron and silicon are the major impurities.

2xxx Series. These alloys require solution heat treatment to obtain optimum properties; in the solution heat-treated condition, mechanical properties are similar to, and sometimes exceed, those of low-carbon steel. In some instances, precipitation heat treatment (aging) is employed to further increase mechanical properties. This treatment increases yield strength, with attendant loss in elongation; its effect on tensile strength is not as great. The alloys in the 2xxx series do not have as good corrosion resistance as most other aluminum alloys, and under certain conditions they may be subject to intergranular corrosion. Alloys in the 2xxx series are good for parts requiring good strength at temperatures up to 150 °C (300 °F). Except for alloy 2219, these alloys have limited weldability, but some alloys in this series have superior machinability.

3xxx Series. These alloys generally are non-heat treatable but have about 20% more strength than 1xxx series alloys. Because only a limited percentage of manganese (up to about 1.5%) can be effectively added to aluminum, manganese is used as major element in only a few alloys.

4xxx Series. The major alloying element in 4xxx series alloys is silicon, which can be added in sufficient quantities (up to 12%) to cause substantial lowering of the melting range. For this reason, aluminum-silicon alloys are used in welding wire and as brazing alloys for joining aluminum, where a lower melting range than that of the base metal is required. The alloys containing appreciable amounts of silicon become dark gray to charcoal when anodic oxide finishes are applied and hence are in demand for architectural applications.

5xxx Series. The major alloying element is Magnesium an when it is used as a major alloying element or with manganese, the result is a moderate-to-high-strength work-hardenable alloy. Magnesium is considerably more effective than manganese as a hardener, about 0.8% Mg being equal to 1.25% Mn, and it can be added in considerably higher quantities. Alloys in this series possess good welding characteristics and relatively good resistance to corrosion in marine atmospheres. However, limitations should be placed on the amount of cold work and the operating temperatures (150 degrees F) permissible for the higher-magnesium alloys to avoid susceptibility to stress-corrosion cracking.

6xxx Series. Alloys in the 6xxx series contain silicon and magnesium approximately in the proportions required for formation of magnesium silicide (Mg2Si), thus making them heat treatable. Although not as strong as most 2xxx and 7xxx alloys, 6xxx series alloys have good formability, weldability, machinability, and relatively good corrosion resistance, with medium strength. Alloys in this heat-treatable group may be formed in the T4 temper (solution heat treated but not precipitation heat treated) and strengthened after forming to full T6 properties by precipitation heat treatment.

7xxx Series. Zinc, in amounts of 1 to 8% is the major alloying element in 7xxx series alloys, and when coupled with a smaller percentage of magnesium results in heat-treatable alloys of moderate to very high strength. Usually other elements, such as copper and chromium, are also added in small quantities. 7xxx series alloys are used in airframe structures, mobile equipment, and other highly stressed parts. Higher strength 7xxx alloys exhibit reduced resistance to stress corrosion cracking and are often utilized in a slightly overaged temper to provide better combinations of strength, corrosion resistance, and fracture toughness.

Titanium Alloys

Titanium alloys are metallic materials which contain a mixture of titanium and other chemical elements. Such alloys have very high tensile strength and toughness (even at extreme temperatures), light weight, extraordinary corrosion resistance, and ability to withstand extreme temperatures. However, the high cost of both raw materials and processing limit their use to military applications, aircraft, spacecraft, medical devices, connecting rods on expensive sports cars and some premium sports equipment and consumer electronics. Auto manufacturers Porsche and Ferrari also use titanium alloys in engine components due to its durable properties in these high stress engine environments.
Titanium Alloys are generally classified into four main categories :

  1. Alpha alloys which contain neutral alloying elements (such as tin) and/ or alpha stabilisers (such as aluminium or oxygen) only. These are not heat treatable.
  2. Near-alpha alloys contain small amount of ductile beta-phase. Besides alpha-phase stabilisers, near-alpha alloys are alloyed with 1-2% of beta phase stabilizers such as molybdenum, silicon or vanadium.
  3. Alpha & Beta Alloys, which are metastable and generally include some combination of both alpha and beta stabilisers, and which can be heat treated.
  4. Beta Alloys, which are metastable and which contain sufficient beta stabilisers (such as molybdenum, silicon and vanadium) to allow them to maintain the beta phase when quenched, and which can also be solution treated and aged to improve strength.

Generally, beta-phase titanium is stronger yet less ductile and alpha-phase titanium is more ductile. Alpha-beta-phase titanium has a mechanical property which is in between both. Titanium dioxide dissolves in the metal at high temperatures, and its formation is very energetic. These two factors mean that all titanium except the most carefully purified has a significant amount of dissolved oxygen, and so may be considered a Ti-O alloy. Oxide precipitates offer some strength (as discussed above), but are not very responsive to heat treatment and can substantially decrease the alloy’s toughness. Many alloys also contain titanium as a minor additive, but since alloys are usually categorized according to which element forms the majority of the material, these are not usually considered to be “titanium alloys” as such. See the sub-article on titanium applications.

Titanium alone is a strong, light metal. It is as strong as steel, but 45% lighter. It is also twice as strong as aluminium but only 60% heavier. Titanium is not easily corroded by sea water, and thus is used in propeller shafts, rigging and other parts of boats that are exposed to sea water. Titanium and its alloys are used in airplanes, missiles and rockets where strength, low weight and resistance to high temperatures are important. Further, since titanium does not react within the human body, it and its alloys are used to create artificial hips, pins for setting bones, and for other biological implants.

The ASTM defines a number of alloy standards with a numbering scheme for easy reference :

Grade 1-4 are unalloyed and considered commercially pure or “CP”. Generally the tensile and yield strength goes up with grade number for these “pure” grades. The difference in their physical properties is primarily due to the quantity of interstitial elements. They are used for corrosion resistance applications where cost and ease of fabrication and welding are important. Grade 5, also known as Ti6Al4V, Ti-6Al-4V or Ti 6-4, is the most commonly used alloy. It has a chemical composition of 6% aluminium, 4% vanadium, 0.25% (maximum) iron, 0.2% (maximum) oxygen, and the remainder titanium. Grade 5 is used extensively in Aerospace, Medical, Marine, and Chemical Processing. It is used for connecting rods in ICEs. It is significantly stronger than commercially pure titanium while having the same stiffness and thermal properties (excluding thermal conductivity, which is about 60% lower in Grade 5 Ti than in CP Ti). Among its many advantages, it is heat treatable. This grade is an excellent combination of strength, corrosion resistance, weld and fabricability. In consequence, its uses are numerous such as for military aircraft or turbines. It is also used in surgical implants Generally, it is used in applications up to 400 degrees Celsius. Its properties are very similar to those of the 300 stainless steel series, especially 316. It has a density of roughly 4420 kg/m3, Young’s modulus of 110 GPa, and tensile strength of 1000 MPa. By comparison, annealed type 316 stainless steel has a density of 8000 kg/m3, modulus of 193 GPa, and tensile strength of only 570 MPa. And tempered 6061 aluminium alloy has 2700 kg/m3, 69 GPa, and 310 MPa, respectively. Grade 6 contains 5% aluminium and 2.5% tin. It is also known as Ti-5Al-2.5Sn. This alloy is used in airframes and jet engines due to its good weldability, stability and strength at elevated temperatures. Grade 7 contains 0.12 to 0.25% palladium. This grade is similar to Grade 2. The small quantity of palladium added gives it enhanced crevice corrosion resistance at low temperatures and high pH. Grade 7H contains 0.12 to 0.25% palladium. This grade has enhanced corrosion resistance.

Grade 9 contains 3.0% aluminium and 2.5% vanadium. This grade is a compromise between the ease of welding and manufacturing of the “pure” grades and the high strength of Grade 5. It is commonly used in aircraft tubing for hydraulics and in athletic equipment. Grade 11 contains 0.12 to 0.25% palladium. This grade has enhanced corrosion resistance. Grade 12 contains 0.3% molybdenum and 0.8% nickel. Grades 13, 14, and 15 all contain 0.5% nickel and 0.05% ruthenium. Grade 16 contains 0.04 to 0.08% palladium. This grade has enhanced corrosion resistance. Grade 16H contains 0.04 to 0.08% palladium. Grade 17 contains 0.04 to 0.08% palladium. This grade has enhanced corrosion resistance. Grade 18 contains 3% aluminium, 2.5% vanadium and 0.04 to 0.08% palladium. This grade is identical to Grade 9 in terms of mechanical characteristics. The added palladium gives it increased corrosion resistance. Grade 19 contains 3% aluminium, 8% vanadium, 6% chromium, 4% zirconium, and 4% molybdenum. Grade 20 contains 3% aluminium, 8% vanadium, 6% chromium, 4% zirconium, 4% molybdenum and 0.04% to 0.08% palladium. Grade 21 contains 15% molybdenum, 3% aluminium, 2.7% niobium, and 0.25% silicon. Grade 23 contains 6% aluminium, 4% vanadium, 0.13% (maximum) Oxygen. Improved ductility and fracture toughness with some reduction in strength. Grade 24 contains 6% aluminium, 4% vanadium and 0.04% to 0.08% palladium. Grade 25 contains 6% aluminium, 4% vanadium and 0.3% to 0.8% nickel and 0.04% to 0.08% palladium. Grades 26, 26H, and 27 all contain 0.08 to 0.14% ruthenium. Grade 28 contains 3% aluminium, 2.5% vanadium and 0.08 to 0.14% ruthenium. Grade 29 contains 6% aluminium, 4% vanadium and 0.08 to 0.14% ruthenium. Grades 30 and 31 contain 0.3% cobalt and 0.05% palladium. Grade 32 contains 5% aluminium, 1% tin, 1% zirconium, 1% vanadium, and 0.8% molybdenum. Grades 33 and 34 contain 0.4% nickel, 0.015% palladium, 0.025% ruthenium, and 0.15% chromium . Grade 35 contains 4.5% aluminium, 2% molybdenum, 1.6% vanadium, 0.5% iron, and 0.3% silicon. Grade 36 contains 45% niobium. Grade 37 contains 1.5% aluminium. Grade 38 contains 4% aluminium, 2.5% vanadium, and 1.5% iron. This grade was developed in the 1990s for use as an armor plating. The iron reduces the amount of Vanadium needed as a beta stabilizer. Its mechanical properties are very similar to Grade 5, but has good cold workability similar to grade 9.

Magnesium Alloys

Magnesium alloys are mixtures of magnesium with other metals (called an alloy), often aluminium, zinc, manganese, silicon, copper, rare earths and zirconium. Magnesium is the lightest structural metal. Magnesium alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys. Plastic deformation of the hexagonal lattice is more complicated than in cubic latticed metals like aluminum, copper and steel. Therefore magnesium alloys are typically used as cast alloys, but research of wrought alloys has been more extensive since 2003. Cast magnesium alloys are used for many components of modern cars, and magnesium block engines have been used in some high-performance vehicles, die-cast magnesium is also used for camera bodies and components in lenses.

Copper Alloys

Copper alloys are metal alloys that have copper as their principal component. They have high resistance against corrosion. The best known traditional types are bronze, where tin is a significant addition, and brass, using zinc instead. Both these are imprecise terms, and today the term copper alloy tends to be substituted, especially by museums. The similarity in external appearance of the various alloys, along with the different combinations of elements used when making each alloy, can lead to confusion when categorizing the different compositions. There are as many as 400 different copper and copper-alloy compositions loosely grouped into the categories: copper, high copper alloy, brasses, bronzes, copper nickels, copper–nickel–zinc (nickel silver), leaded copper, and special alloys. The following table lists the principal alloying element for four of the more common types used in modern industry, along with the name for each type. Historical types, such as those that characterize the Bronze Age, are vaguer as the mixtures were generally .

Nickel Alloys

Nickel-base alloys are used in many applications where they are subjected to harsh environments at high temperatures. Nickel-chromium alloys or alloys that contain more than about 15% Cr are used to provide both oxidation and carburization resistance at temperatures exceeding 760°C. Nickel-base alloys offer excellent corrosion resistance to a wide range of corrosive media. However, as with all types of corrosion, many factors influence the rate of attack. The corrosive media itself is the most important factor governing corrosion of a particular metal. Low-Expansion Alloys Nickel was found to have a profound effect on the thermal expansion of iron.Alloys can be designed to have a very low thermal expansion or display uniform and predictable expansion over certain temperature ranges. Iron-36% Ni alloy (Invar) has the lowest expansion of the Fe-Ni alloys and maintains nearly constant dimensions during normal variations in atmospheric temperature.The addition of cobalt to the nickel-iron matrix produces alloys with a low coefficient of expansion, a constant modulus of elasticity, and high strength. Electrical Resistance Alloys. Several alloy systems based on nickel or containing high nickel contents are used in instruments and control equipment to measure and regulate electrical characteristics (resistance alloys) or are used in furnaces and appliances to generate heat (heating alloys).

Alnico
Alnico is an acronym referring to iron alloys which in addition to iron are composed primarily of aluminium (Al), nickel (Ni) and cobalt (Co), hence al-ni-co, with the addition of copper, and sometimes titanium. Alnico alloys are ferromagnetic, with a high coercivity (resistance to loss of magnetism) and are used to make permanent magnets. Before the development of rare earth magnets in the 1970s, they were the strongest type of magnet. Other trade names for alloys in this family are: Alni, Alcomax, Hycomax, Columax, and Ticonal. The composition of alnico alloys is typically 8–12% Al, 15–26% Ni, 5–24% Co, up to 6% Cu, up to 1% Ti, and the balance is Fe. The development of alnico began in 1931, when T. Mishima in Japan discovered that an alloy of iron, nickel, and aluminum had a coercivity of 400 oersted (Oe), double that of the best magnet steels of the time. Alnico alloys make strong permanent magnets, and can be magnetized to produce strong magnetic fields. Of the more commonly available magnets, only rare-earth magnets such as neodymium and samarium-cobalt are stronger. Alnico magnets produce magnetic field strength at their poles as high as 1500 gauss (0.15 tesla), or about 3000 times the strength of Earth’s magnetic field. Some brands of alnico are isotropic and can be efficiently magnetized in any direction. Other types, such as alnico 5 and alnico 8, are anisotropic, with each having a preferred direction of magnetization, or orientation.

Alumel
Alumel is an alloy consisting of approximately 95% nickel, 2% manganese, 2% aluminium and 1% silicon. This magnetic alloy is used for thermocouples and thermocouple extension wire. Alumel is a registered trademark of Hoskins Manufacturing Company. Properties of Alumel:

Chromel
Chromel is an alloy made of approximately 90 percent nickel and 10 percent chromium that is used to make the positive conductors of ANSI Type E (chromel-constantan) and K (chromel-alumel) thermocouples. It can be used up to 1100 °C in oxidizing atmospheres. Chromel is a registered trademark of the Hoskins Manufacturing Company. Chromel A is an alloy containing 80% of nickel and 20% chromium (by weight). It is used for its excellent resistance to high-temperature corrosion and oxidation. It is also commonly called Nichrome 80-20 and used for electric heating elements.

Cupronickel
Cupronickel or copper-nickel (sometimes incorrectly referred to as “cupernickel”) is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese. Cupronickel is highly resistant to corrosion in seawater, because its electrode potential is adjusted to be neutral with regard to seawater. Because of this, it is used for piping, heat exchangers and condensers in seawater systems as well as marine hardware, and sometimes for the propellers, crankshafts and hulls of premium tugboats, fishing boats and other working boats. Cupronickel Cupronickel or copper-nickel (sometimes incorrectly referred to as “cupernickel”) is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese. Cupronickel is highly resistant to corrosion in seawater, because its electrode potential is adjusted to be neutral with regard to seawater. Because of this, it is used for piping, heat exchangers and condensers in seawater systems as well as marine hardware, and sometimes for the propellers, crankshafts and hulls of premium tugboats, fishing boats and other working boats.

Ferronickel
In 2008, the major ferronickel-producing countries were Japan (301,000 t), New Caledonia (144,000 t) and Colombia (105,000 t). Together, these three countries accounted for about 51% of world production if China is excluded. Ukraine, Indonesia, Greece, and Macedonia, in descending order of gross weight output, all produced between 68,000 t and 90,000 t of ferronickel, accounting for an additional 31%, excluding China. China was excluded from statistics because its industry produced large tonnages of nickel pig iron in addition to a spectrum of conventional ferronickel grades, for an estimated combined output of 590,000 t gross weight. The nickel content of individual Chinese products varied from about 1.6% to as much as 80%, depending upon customer end use.

Nickel silver
Nickel silver, also known as German silver, Argentann, paktong, new silver, nickel brass, or alpacca (or alpaca), is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver first became popular as a base metal for silver plated cutlery and other silverware, notably the electroplated wares called EPNS (electro-plated nickel silver). It is used in zippers, better-quality keys, costume jewellery, for making musical instruments (e.g., cymbals, saxophones), and is preferred for the track in electrically powered model railway layouts as its oxide is conductive. It is widely used in the production of coins (e.g. GDR marks, Portuguese escudo). Its industrial and technical uses include marine fittings and plumbing fixtures for its corrosion resistance, and heating coils for its high electrical resistance.

Hastelloy
Hastelloy is the registered trademark name of Haynes International, Inc. The trademark is applied as the prefix name of a range of twenty two different highly corrosion-resistant metal alloys loosely grouped by the metallurgical industry under the material term “superalloys” or “high-performance alloys”. The predominant alloying ingredient is typically the transition metal nickel. Other alloying ingredients are added to nickel in each of the subcategories of this trademark designation and include varying percentages of the elements molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon, and tungsten. The primary function of the Hastelloy super alloys is that of effective survival under high-temperature, high-stress service in a moderately to severely corrosive, and/or erosion prone environment where more common and less expensive iron-based alloys would fail, including the pressure vessels of some nuclear reactors, chemical reactors, distillation equipment and pipes and valves in chemical industry.

Inconel
Inconel is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based superalloys. Inconel alloys are typically used in high temperature applications. It is often referred to in English as “Inco” (or occasionally “Iconel”). Common trade names for Inconel include: Inconel 625, Chronin 625, Altemp 625, Haynes 625, Nickelvac 625 and Nicrofer 6020. Inconel alloys are oxidation and corrosion resistant materials well suited for service in extreme environments.When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high temperature applications where aluminum and steel would succumb to creep as a result of thermally-induced crystal vacancies (see Arrhenius equation). Inconel’s high temperature strength is developed by solid solution strengthening or precipitation strengthening, depending on the alloy. In age hardening or precipitation strengthening varieties, small amounts of niobium combine with nickel to form the intermetallic compound Ni3Nb or gamma prime. Gamma prime forms small cubic crystals that inhibit slip and creep effectively at elevated temperatures.

Monel
Monel is a trademark of Special Metals Corporation for a series of nickel alloys, primarily composed of nickel (up to 67%) and copper, with some iron and other trace elements. Monel was created by David H. Browne, chief metallurgist for International Nickel Co. Monel alloy 400 is binary alloy of the same proportions of nickel and copper as is found naturally in the nickel ore from the Sudbury (Ontario) mines. Monel was named for company president Ambrose Monell, and patented in 1906. One L was dropped, because family names were not allowed as trademarks at that time.

Nichrome
Nichrome is a trademark for a non-magnetic alloy of nickel, chromium, and often iron, usually used as a resistance wire, produced by the Driver-Harris Company. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various applications. It is silvery-grey in colour, is corrosion-resistant, and has a high melting point of about 1400 °C (2552 °F). Due to its relatively high electrical resistivity and resistance to oxidation at high temperatures, it is widely used in electric heating elements, such as in hair dryers, electric ovens, soldering iron, toasters, and even electronic cigarettes. Typically, Nichrome is wound in coils to a certain electrical resistance, and current is passed through to produce heat.

Nickel titanium
Nickel titanium, also known as nitinol, is a metal alloy of nickel and titanium, where the two elements are present in roughly equal atomic percentages.Nitinol alloys exhibit two closely related and unique properties: shape memory and superelasticity (also called pseudoelasticity). Shape memory refers to the ability of nitinol to undergo deformation at one temperature, then recover its original, undeformed shape upon heating above its “transformation temperature”. Superelasticity occurs at a narrow temperature range just above its transformation temperature; in this case, no heating is necessary to cause the undeformed shape to recover, and the material exhibits enormous elasticity, some 10-30 times that of ordinary metal.