alloy

The entire crown of the Chrysler Building in New York is clad with "Enduro KA-2" metal, a stainless steel alloy developed in Germany

A combination of a metal with one or more other metals or non-metals, such as carbon or phosphorus. An alloy may be a compound of the metals, a solid solution of them, a heterogeneous mixture, or any combination of these. The resultant physical properties differ from those of the components. Alloys are general harder and stronger, and have lower melting points, than their constituent elements. Combinations with the lowest melting point are called eutectic mixtures. In the table of alloys below, 26 elements are involved.

Alloys are useful because their properties can be adjusted as desired by varying the proportions of the constituents. Very few metals are used today in a pure state. Alloys are formed by mixing their molten components. The structures of alloys consisting mainly of one component may be substitutional or interstitial, depending on the relative sizes of the atoms. The study of alloy structures in general is complex.

The commonest alloys are the different forms of steel, which all contain a large proportion of iron and small amounts of carbon and other elements. Brass and bronze, two well-known and ancient metals, are alloys of copper, while pewter is an alloy of tin and lead. The very light but strong alloys used in aircraft construction are frequently alloys of aluminum and magnesium. Solders contain tin with lead and bismuth; type metal is an alloy of lead, tin, and some antimony. Among familiar alloys are those used in coins: modern "silver" coinage in most countries is an alloy of nickel and copper. Special alloys are used for such purposes as die-casting, dentistry, high-temperature applications, and for making thermocouples, magnets, and low-expansion materials.

A selection of alloys
Name	Composition expressed as percentages	Properties and uses
alnico	Fe 60, Ni 20, Al 10, Co 10	permanent magnet
Babbitt metal	Sn (predominates), Sb, Cu (+Pb)	used for bearings, anti-friction metal
brass	Cu with 20–35 Zn	decorative
bronze	Cu with 5–8 Sn	primitive tools, coinage
carboloy	W₂C₂ with 10 Cu	very hard alloy, grinding tools
cast iron	impure Fe, C up to 4½ with Mn, P, Si, and S traces	decorative work, weights
cupronickel	Cu 80, Ni 20 (coinage 25-75)	coinage
delta metal	Cu 55–60, Zn c. 40, Fe 2–4	bearings, marine propellers
dow metal	Al, Mg	aircraft and car parts
dental alloy	Ag, Cu, Zn, Sn	tooth fillings
duralim	Al 93–95½, Cu 3½–5½, Mn ½–¾, Mg ½–¾	aircraft frames
Dutch metal	Cu with 30–35 Zn	bronze in gold leaf form
E-alloy	Al 78, Zn 20, Cu 2; Al 96, Zn 2, Cu 2	castings
electrum	Au with 15–45 Ag	coins (ancient times)
Frary metal	Pb 97, Ba 2, Ca 1	bearings
German metal	Cu 56–65, Zn 24–28, Ni 7–20	metal fittings, metal ware (often electroplated)
gun metal	Cu 88, Sn 8–10, Zn 2–4	ordnance
hiduminium	Al with small Cu, Ni, Mg, Si additions	aircraft parts
illium	complex of Co, Cr, Fe, Mn, Mb, Ni, and W	acid resistant
Jae metal	Ni 70, Cu 30	shunts on magnetic instruments
Lipowitz's alloy	Bi 50, Pb 27, Sn 13, Cd 10	very low melting point (60°C)
magnolia metal	Pb 80, Sb 15, Sn 5	medium duty bearings
monel metal	Ni 68, Cu 29½, Fe 1¼,	resistant to steam corrosion
Muntz metal, yellow metal	Cu 60, Zn 40	resistant to seawater corrosion
nichrome	Ni 60, Fe 20, Cr 20	filament wires
nickel silver	Cu 55–63, Ni 10–30, Zn 7–35	electroplated articles, hence E.P.N.S.
pewter	Sn 80, Pb 20, traces of Sb	modern pewter Pb replaced by Sb with some Cu and Bi
permalloy	Ni 77.5, Fe 22.5 (sometimes with traces of Co, Cr, Cu, and Mo)	magnetic properties, transformers, submarine cable parts
phosphorbronze	Cu 90, Sn 9½, P ½28	castings, bearings, and rsilient strip
pinchbeck	Cu 89–93, Zn 7–11	imitation gold, jewellery
"silver" alloy	Hg–Sn amalgam	"silver" backing for mirrors
solder	Sn½, Pb 33½	plumbing
speculum	Cu 60–70, Sn 30–40	high polish surfaces, plating
stainless steel	Fe 78–86, Cr 12–20, Ni 2	corrosion resistant culinary, sterile vessels, decorative
steel	essentially Fe with C ½–1½ with special purpose additices of Cr, Mn, Mb, Ni, Si, Al, Cu, Co, Ti, W, V	multifarious
stellite	Co 43, Cr 43, W 14 et al.	surgical and other cutting tools
tombac	Cu 71–90, Zn 10–29	cartridge cases
type metal	Pb 80–86, Sb 11–20, Sn 3–11	lino-, mono-, and stereotype fonts
white gold	Au with Ni	platinum substitute
Woods metal	Bi 50, Pb 25, Sn 12½, Cd 12½	low melting point, fire sprinklers
X-40	Co 55, Cr 25, Ni 9, W 7, C ½, Fe ½, traces of Mn, Si	non-creep at high temperatures, gas turbine rotor blades
Y-alloy	Al 93, Cu 4, Ni 2, Mn 1

Related categories

• INDUSTRIAL CHEMISTRY
• INORGANIC CHEMISTRY

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