Alloys
An alloy is a mixture of two or more metals fused together in molten state. Metals when melted tend to dissolve in one another forming alloys. The various properties of a metal like malleability, ductility, strength, hardness, resistance to corrosion and appearance can be improved by mixing with other metals. Alloys have properties different from its constituents.
Al - Alloy
property / Reason for alloying
Uses
Duralumin (Al, Mg, Mn, Cu)
Light, strong, resistant to corrosion
Aircraft, tools, pressure cooker
Magnalium (Al, Mg)
Light, hard, tough, corrosion resistant
Aircrafts, scientific instruments
Copper Alloys
Cu
Zn
Sn
Pb
Ni
Brass
60-80%
40-20%
-
-
-
Bronze
80%
2%
18%
-
-
Gun metal
90%
-
10%
-
-
German
-
-
-
-
-
Silver
50%
30%
-
-
20%
Bell metal
80%
-
20%
-
-
Cu - Alloy
Property / Reason for alloying
Uses
Brass
Lustrous, easily cast, Alloy is Malleable, ductile, harder than Cu
Electrical fittings. Medals, hardware
Bronze
Hard, brittle, takes up polish
Statues, medals, coins
Bell metal
Hard, brittle, sonorous Alloy is more sonorous than Cu or Sn
Bells, gongs
Gun metal
Hard, brittle, easily cast
Barrels, cannon
German silver
Hard, silvery, takes up polish
Decorative articles
Steel Alloys
Steel - Alloy
Property / Reason for alloying
uses
Stainless steel (Fe, C, Ni, Cr)
Lustrous, resistant to corrosion, high tensile strength
Alloy: Acquires brilliant silvery shine on alloying with Ni, Cr
Utensils, cutlery, automobile parts
Nickel Steel (Fe, C, Ni)
Hard, corrosion resistant, elastic Light, hard, tough, corrosion resistant
Cables, aircraft parts and propeller shafts
Tungsten steel
Very hard Corrosion resistant
Alloy: Acquires hardness on alloying with tungsten (W)
High speed machine parts
Alloying of Gold
From the first discoveries of gold in ancient times, its beauty and the ease with which it could be worked inspired craftsmen to create it into ornaments, not just for adornment, but as symbols of wealth and power Pure gold is used in those parts of the world where jewellery is purchased as much for in- vestment as it is for adornment, but it tends to be vulnerable to scratching. Elsewhere, it is usually mixed, or alloyed, with other metals. Not only do they harden it, but influence the colour; white shades are-achieved by alloying gold with silver, nickel or palladium; red alloys contain mainly copper. A harder alloy is made by adding nickel or a tiny percentage of titanium.
The.proportion of gold in jewellery is measured on the carat (or karat) scale. The word carat comes from the carob seed, which was originally used to balance scales in Oriental bazaars. Pure gold is designated 24 carat, which compares with the "fineness" by which bar gold is defined.
Pure Gold alloys
Caratage
Fineness
% Gold
24
1000
100
22
916.7
91.67
18
750
75
14
583.3
58.3
10
416.7
41.67
9
375
37.5
The most widely used alloys for jewellery in Europe are 18 and 14 carat, although 9 carat is popular in Britain. Portugal has a unique designation of 19.2 carats. In the United States 14 carat predominates, with some 10 carat. In the Middle East, India and South East Asia, jewellery is traditionally 22 carat (sometimes even 23 carat). In China, Hong Kong and some other parts of Asia, "chuk kam" or pure goldjewellery of990 fineness (almost 24 carat) is popular. In many countries the law requires that every item of gold jewellery is clearly stamped with its caratage. This is often controlled through hallmarking, a system which originated in London at Goldsmiths' Hall in the 14th century. Today it is compulsory in such countries as Britain, France, the Netherlands, Morocco, Egypt, and Bahrain. Where there is no compulsory marking manufacturers themselves usually stamp the jewellery both with their own individual identifying mark and the caratage or fineness.
Some common alloys and what we use them for
There are zillions of different alloys used for zillions of different purposes. We've listed 20 of the rriore common (or otherwise interesting) ones in the table below. There are lots of different variations on most alloys and the precise mixture can vary widely, so the percentage figures you see quoted in different books will often not agree exactly.
Alloy
Components
Typical uses
Alnico
Iron (50%+), aluminum (8-12%), nickel (15-25%), cobalt (5-40%), plus other metals such as copper and titanium.
Magnets in loudspeakers and pickups in electric guitars.
Amalgam
Mercury (45-55%), plus silver, tin, copper, and zinc.
Dental fillings.
Babbitt metal ("white metal")
Tin (90%), antimony (7-15%), copper (4-10%).
Friction-reducing coating in machine bearings.
Brass
Copper (65-90%), zinc (10-35%).
Door locks and bolts, brass musical instruments, central heating pipes.
Bronze
Copper (78-95%), tin (5-22%), plus manganese, phosphorus, aluminum, or silicon.
Decorative statues, musical
Cast iron
Iron (96-98%), carbon (2-4%), plus silicon.
Metal structures such as bridges and heavy-duty cookware.
Cupro-nickel (copper nickel)
Copper (75%), nickel (25%), plus small amounts of manganese.
Coins.
Duralumin
Aluminum (94%), copper (4.5-5%), magnesium (0.5-1.5%).
Automobile and aircraft body parts, military equipment.
Gunmetal
Copper (80-90%), tin (3-10%), zinc (2-3%), and phosphorus.
Guns, decorative items.
Magnox
Magnesium, aluminum.
Nuclear reactors.
Nichrome
Nickel (80%), chromium (20%).
Firework ignition devices, heating elements in electrical appliances.
Nitinol
Nickel (50-55%), titanium (45-50%).
Shape memorey alloy used in medical items, spectacle frames that spring back to shape, and temperature switches.
Pewter
Tin (80-99%) with copper, lead, and antimony.
Ornaments, used to make tableware before glass became more common.
Solder
Tin (50-70%), lead (30-50%), copper, antimony, and other metals.
Connecting electrical components into cirecuits.
Steel (general )
Iron (80-98%), carbon (0.2-2%), plus other metals such as chromium, manganese, and vanadium.
Metal structures, car and airplane part, and many other uses.
Steel (stainless)
Iron (50%+), chromium (1030%), plus smaller amounts of carbon, nickel, manganese, molybdenum, and other metals.
Jewelry, medical tools, tableware.
Stellite
Cobalt (67%), chromium (28%), tungsten (4%), nickel (1%).
Coating for cutting tools such as saw teeth, lathes, and chainsaws.
Sterling silver
Silver (92.5%), copper (7.5%).
Cutlery,jewelry, medical tools,
musical instruments.
White gold (18 carat)
Gold (75%), palladium (17%), silver (4%), copper (4%)
Jewelry.
Wood's metal
Bismuth (50%), lead (26.7), tin (13.3%), cadmium (10%).
Solder, melting element in fire sprinkler systems.
Other Metal Alloys
Nickel silver
is a metal alloy of copper with nickel and often but not always zinc. It is named for its silvery appearance, but contains no elemental silver unless plated. Other common names for this alloy are German silver, paktong, new silver and alpacca (or alpaca).
Monel
Monel (or monel metal) is a trademarked name for a range of corrosion-resistant bright metal alloys containing typically 67 percent nickel, 30 percent copper, and trace proportions of iron, manganese, and other elements. It is not a synonym for Nickel Silver and should not be confused with it. Monel is more expensive than Nickel Silver because of the high proportion of nickel and its more specialist applications.
Gun Metal
An alloy in the bronze family, used especially where resistance to wear and corrosion is desired. Clasically, an alloy of Cu 88 %, Sn 10%, Zn 2%, traditionally used for making cannon and other industrial products. Also used loosely to describe other dark-grey cast metals such as found in toys, badges, buckles etc.
Pinchbeck
Pinchbeck is a yellow metal alloy in the brass family. Invented by Christopher Pinchbeck in the 18th century, it was claimed to be a secret recipe, but is generally believed to be 83% copper and 17% zinc. This ratio optimises the gold matching colour of the alloy. Commonly known as "poor man's gold". It and similar alloys were widely used in costume jewellery, and as the metal substrate for fire gilding and (from 1840) gilt electroplating. Now included under the generic name "Gilding Metal".
Spelter
Spelter is an alternative name for the metal zinc, especially when used in decorative arts manufacture and casting. Spelter castings were often patinated to imitate more valuable bronze.
Tutania
Tutania is an alloy of copper, antimony, zinc and tin patented in 1770 by William Tutin whose Birmingham firm (Tutin and Haycroft) used it in commercial production of housewares.
Cupro-Nickel
A silvery-coloured binary alloy of copper and nickel. Widely used for minting coinage. It is also called copper-nickel, especially in US usage. In the UK it has been used since 1947 for "silver" coins, usually in an alloy ofCu 75%, Ni 25%. The alloy in the current 20p coin of the UK is Cu 84%, Ni 16%.
Bronze
Any of various alloys of copper with tin and often zinc. Widely used for minting coinage. In the UK bronze coinage (the copper-coloured coins of 1860-1992) the alloy was Cu 95.5%, Sn 3%, Zn 1.5%
Nickel Brass
Any of various brass coloured aIIoys of copper with zinc and a small component of nickel. Widely used for minting coinage. In the UK's nickel brass coinage (the twelve-sided threepenny piece) the alloy was Cu 79%, Zn 20%, Ni 1%.
Britannia Metal
Britannia metal is another name for pewter in its modem lead-free formulation, usually 91% tin, 7.5%antimony, 1.5% copper.