An alloy may be defined as coherent metallic mass produced by the intimate association of two or more metals. In some cases also the introduction of non-metals such as carbon, silicon, phosphorus, boron, sulphur and even nitrogen or oxygen may produce marked effects. It is important that thousands of combinations resulting in useful alloys are possible.

Important non-ferrous alloys are discussed below:

1. Copper Alloys:

The copper alloys can be divided into two principal classes:

I. Brasses and


II. Bronzes.

The ‘brasses’ are primarily alloys of copper and zinc and “bronzes’ of copper and tin, but there are numerous modifications of them produced by the addition of smaller amounts of other elements.

In addition there are cupro-nickels, containing principally copper and nickel, and nickel silvers (German silvers) in which zinc of brass is partially replaced by nickel.

I. Brasses:


With range of composition from 5 to 45 percent of zinc, the brasses are among the most useful alloys. They possess excellent mechanical properties, and are corrosion resistant and are readily machinable.

Modified Brasses:

The mechanical properties or corrosion resistance of the brasses is in some cases greatly improved by the introduction of relatively small quantities of one or more other metals.

Some of the more common of these are given below:


1. Manganese Brass:

The alloy referred to under this head is generally spoken of as manganese bronze, but it is in reality a brass since the main constituents are copper and zinc. The composition varies considerably, but the following percentages may be regarded as typical; copper = 60%; zinc = 38 to 42%; tin = 0.5 to 1.5%; iron = 0.5 to 1.5%; manganese 0 to 0.5% and sometimes a little aluminium. The manganese is generally added in the form of ferromanganese; this accounts for the presence of iron, which in itself has important effects.


(i) It is exceedingly tough.


(ii) It has high resistance even in sea water.

(iii) It is very active in reducing the oxides of other metals, an action that is highly useful.

(iv) In addition to its action as deoxidiser, manganese hardens and strengthens the alloy.

(v) In cast form, the tensile strength of the manganese brass lies in the neighbourhood of 500 MN/m2 and this is somewhat improved by working, as by rolling and forging.



It is used for pump rods, hydraulic rams, valves and cylinders, tubes, propellers, nuts, bolts etc.

2. Iron Brass:

One of the most widely used alloys of this type is known as delta metal, its composition is- Cu = 60%, Zn = 37%, Fe = 3% (also some quantity of Ni or Mn).


(i) It is hard, strong and tough.

(ii) It is easily cast.

(iii) Its tensile strength is about two-fifths greater than brass of similar composition with the iron omitted.

(iv) It resists corrosion.


It is used for mild steel if corrosion is to be resisted.

3. Tin Brass:

Tin is one of the most useful metals added to brass. It increases the hardness and tensile strength but amount employed should not exceed about 2%, because with higher amounts the ductility begins to decrease. Its composition is Cu = 60%, Zn = 39%, Zn = 1%. It is also some time called naval brass since it is used in naval construction.


(i) It has high strength and hardness.

(ii) It has excellent corrosion resistance property.

(iii) Its tenacity is high and has good working qualities.

4. Lead Brass:

In brass that is intended for filing or turning, 1 to 2% of lead is employed to prevent fouling of tools and to cause the turnings to break more readily; this prevents logging of automatic machines. Lead increases the softness of the brass.

It is sometimes added to the brass that is to be worked, but care should be taken to add but a small amount, because it reduces the ductility and strength. Only about 3% will alloy with the brass; if more than this is added it has a tendency to liquate. On this account ‘leaded’ brasses should be chilled quickly when cast.

5. Aluminium Brass:

The amount of aluminium added to brass does not usually exceed 3%. It raises the tensile strength but decreases the ductility. The product has a deep golden colour and resists corrosion better than ordinary brass. It casts well and may be forged or rolled.

II. Bronzes:

These are essentially alloys of copper and tin.

The effect of composition on physical properties is given below:

1. The tensile strength of bronze increases gradually with the amount of tin, reaching a maximum with about 20% of tin, but as the tin increases beyond this amount the tensile strength very rapidly decreases.

2. Bronze is most ductile when it contains about 5% of tin, with this amount it may be rolled satisfactorily at red heat. Bronze is used chiefly for casting.

3. As the amount of tin increases above 5%, the ductility gradually lessens and practically disappears with about 20% of tin; since ductility is co-ordinate with toughness, these alloys are very brittle. They are also very hard.

4. The most useful of bronzes are those that contain from 8 to 11% of tin, since the maximum combined strength and toughness are secured with about these amounts. Bronze containing tin within these limits was formerly, known as gun metal, since because of this strength it was used for making guns, but now steel has entirely replaced it for this purpose. At the present time, the term gun metal is very loosely used and cannot be said to have definite significance.

5. As cast the alloy containing 9% of the tin has a tensile strength of about 215 MN/m2.

6. The bronze containing 4 to 8% tin is called ‘coinage bronze’ and used for making coins and metals.

7. The copper-tin series of alloys containing 15 to 25% of tin is known as ‘bell metal’. Such alloys are very hard and brittle, but are sonorous and are employed, therefore, in making bells.

8. By alloying 2 parts copper with 1 of tin, a very hard, brittle white alloy is produced called ‘spectrum metal’. When highly polished it serves excellently for mirrors and reflectors.

1. Modified Bronzes:

The zinc bronzes usually contain- Cu = 88%, Sn = 8 to 10% and Zn = 4 to 2%.

The presence of the zinc in the bronzes has the following effects:

I. It increases the fluidity of the melted metal and in this way tends to prevent gas flaws in the casting.

II. It also increases the strength and ductility.

III. The specific gravity when cast in sand is about 8.58; the melting point is about 980°C.

2. Phosphor Bronze:

It is certain, however, that whatever good qualities the bronzes might have, they are greatly increased by the addition of phosphorus. The tensile strength, the elasticity and the resistance to fatigue are enormously increased; so much so that it may also be considered as an entirely new alloy.

Phosphorus is best added to bronze in the form of phosphorus copper, a hard brittle substance of white fracture, containing about 8% phosphorus. Upon being added to molten bronze nearly all of the phosphorus oxidizes and escapes, so that most phosphorus bronzes contain no more than a few tenths of 1%. The crystalline structure of two bronzes, one with and the other without phosphorus, as shown by microscope, seems to be the same in both cases. Phosphor bronze is then essentially a deoxidized bronze.

Although phosphorus produces very beneficial results through its activity as deoxidising agent, if there is much of it left in the alloy, it may be decided determent.

Phosphor bronze of proper composition can be forged, drawn, cold rolled and cast. It seems to resist corrosion better than ordinary bronze, especially by sea water, so that it is much used for propeller blades.

On account of its toughness, elasticity and strength it may serve as a substitute for steel as in the manufacture of corrosion-resistant mine cables, ship sheathing, valve parts, springs etc.

3. Silicon Bronzes:

These are copper alloys having 4% of silicon and upto 1% of manganese with small amounts of tin, zinc, iron and aluminium. These are obviously not bronzes since tin is very small. They are available in the market under various trade names. These always have strength of soft steel and at the same time are corrosion resistant. They are used in screws, belts, tubings, pumps etc.

4. Aluminium Bronze:

Its composition is- Cu = 88%; A1 = 8%; Fe = 3%; Sn = 0.5%. Thus it is primarily a copper- aluminium alloy.


(i) This alloy has a high strength.

(ii) It has marked resistance to corrosion.

(iii) Its melting point is about 1040°C.

(iv) Somewhat difficult to cast due to oxidation.

(v) Castings of metal are sound and not liable to segregation, but the aluminium used must be free from impurity, a small quantity of which is found to produce a very marked deterioration.

(vi) The commercial aluminium bronzes are practically non-magnetic, but certain complex bronzes containing appreciable proportions of iron are magnetic.


1. Aluminium bronze is at present most satisfactory copper alloy for die casting, since it causes less corrosion of dies than brass.

2. It is used in making hot stampings although it is not easy to work in this respect as brass or manganese.

3. It is also used in marine work, bearing metal in locomotive.


A disadvantage of aluminium bronze is that it usually develops surface of high electrical resistance when used for current carrying purposes; these films tend to give rise to high electrical resistance and render jointing a matter of difficulty.

5. Beryllium Copper:

This alloy is also sometimes called beryllium bronzes. It contain 2 to 3% of beryllium.


(i) It has a high yield point and high fatigue limit.

(ii) It has excellent cold and hot resistance.

(iii) These alloys can also be heat treated.

(iv) It has Brinell hardness 340 when heated to 800°C and then hardened by subsequent precipitation treatment.


1. It is used for springs, heavy duty electrical switches, cams and bushings.

2. Being non-sparking, it is utilized for making chisels and hammers under conditions where spark might cause an explosion.

6. Copper-Nickel Alloys:

These are copper base alloys.

Addition of nickel to copper improves mechanical properties and resistance to corrosion.

‘Manganin’, a resistance wire with a very low temperature co-efficient of resistance, consists of 80% of copper, 5 percent of nickel and 15% of manganese.

Nickel silvers or German silvers are ternary alloys of copper containing from 5 to 45% of zinc and from 5 to 30% of nickel. They have fair strength, good plasticity and low thermal conductivity. They are used extensively as the base metal on which silver is plated for table ware and for high grade plumbing hardware. They are used for electrical wares and numerous fittings.

2. Aluminium Alloys:

The principal elements which are alloyed with pure aluminium to improve its tensile strength and hardness are copper, silicon, manganese, zinc, magnesium and nickel. One element may be used alone but often two, three or four additions are made to the base metal to produce a metal having specific physical properties.

Copper (for instance) is the main hardening element added while the addition of a small percentage of magnesium to an aluminium copper alloy still further improves the hardness and strength after heat treatment. Strength may also be improved by addition of small quantities of manganese and nickel to a copper-aluminium alloy,

Silicon, is next in importance to copper as a main alloying element, since in combination with magnesium it forms a hard compound known as magnesium silicide which is largely responsible for the hardness obtained on the treatment.

Manganese acts as a strengthening agent and prevents the formation of a course crystalline structure during heat treatment.

Some of the important aluminium alloys are:

1. Duralumin:


Al = 94%, Cu = 4%, Mg, Mn, Si, Fe = 0.5% each.


(i) It can be cast, forged and stamped.

(ii) It has high tensile strength.

(iii) It possesses high electrical conductance.

(iv) It hardens spontaneously when exposed to room temperature.

(v) The alloy is soft enough for a workable period after it has been quenched.

(vi) The temperature employed for the solution heat treatment of the alloy is the lowest that is applicable to any commercial light alloy.

(vii) Specific gravity = 2.8, specific heat = 0.214.

(viii) Melting point = 650°C.

(ix) Brinell hardness- Annealed = 60, age hardened = 100.


1. It is widely used for sheets, tubes, forgings, rivets, nuts, bolts and similar parts.

2. Used in making cables.

3. It is also extensively used for air planes and other machines where weight is a deciding factor.

4. It is also employed in surgical and orthopaedic work and for non-magnetic and other instrument parts.

Heat Treatment:

Annealing is carried out at 360-400°C and the metal is cooled in air. It is then ductile and can be cold worked. Normalising is carried out at a temperature of 490°C plus or minus 10 degrees. After normalising the metal is quenched in clean cold water.

A salt bath is used for heat treatment generally consisting of 50% silver nitrate, with 50% potassium nitrate. For built up fittings a muffle furnace is sometimes used.

2. Y-Alloy:


Al = 92.5%; Cu = 4%; Ni = 2%; Mg = 1.5%.


(i) Its strength at 200°C is better than aluminium.

(ii) It retains its high strength and hardness at high temperature.

(iii) It can be easily cast and hot worked.


1. It is extensively ‘used for such components as piston cylinder heads and crankcases of internal combustion engines.

2. It is also used for die casting, pump rods and in sparking chisel in place of steel.

Heat Treatment and Age Hardening:

The heat treatment range of Y-alloy is 5000°C – 5200°C; this is higher than for aluminium.

It has been found that muffle furnace is best medium for heat treating Y-alloy. The period of treatment at 500°C – 520°C required to bring about solution of age-hardening constituents depends on the fineness of grain and distribution of constituents.

For chilled cast bars, 2.5 cm diameter, about 6 hours are required. For coarser grain material a longer period becomes necessary, whilst for large castings 24 hours or more may be required. In all cases the period of treatment at 500°C – 520°C (solution treatment) must be regulated in relation to the micro-structure. Treatment at the temperature 500°C to 520°C is followed by quenching in boiling water. After quenching, age hardening at room temperature, substantially completes in 5 days.

Age hardening can be accelerated by retaining the alloy immersed in the water at boiling temperature after quenching. Under these conditions age hardening is substantially complete in from 1/2 hour for the wrought to 2 hours for the cast alloy.

By subjecting normally heat-treated material, cast or wrought, to temperatures between 150°C to 250°C the tensile strength and hardness are substantially increased, but the ductility is diminished. Above 250°C permanent softening results.


Y-alloy is annealed in the wrought state by heating it to 350°C to 400°C and allowing it to cool in the air.

3. Hindalium:

Hindalium is an alloy of aluminium, magnesium, manganese, chromium and silicon etc., and is the trade name of the aluminium alloy produced by Hindustan Aluminium Corporation Ltd., Renukoot Distt. Mirzapur (U.P).

It is manufactured as a rolled product (16 gauge) mainly for anodized utensile manufacture. During processing special care is taken to maintain the necessary mechanical and surface characteristics.

Hindalium utensils possess the following advantages:

1. Strong and hard.

2. Cannot be easily scratched.

3. Can take fine finish.

4. Do not absorb much heat and thus save fuel while cooking.

5. Can be easily cleaned.

6. Do not react with the food acids.

7. Low cost (about one-third of stainless steel).

4. Magnelium:

It is an alloy of aluminium, magnesium, copper, nickel and tin etc.

Typical composition of magnelium is:

Al = 85 to 95%

Cu = 0 to 25%

Mg = 1 to 5.5%

Ni = 0 to 1.2%

Sn = 0 to 3%

Fe = 0 to 0.9%

Mn = 0 to 0.03%

Si = 0.2 to 0.6%.


(i) Light weight.

(ii) Tensile strength—annealed state- 200 N/mm2; cold worked state : 280 N/mm2

(iii) Elongation-annealed state : 30%; cold worked state : 7%

(iv) Alloy is brittle.

(v) Castability poor.

(vi) Machinability good.

(vii) Can be welded.


Mostly used in the aircraft and automobile industries.

Some of parts made from magnelium are:

Gearbox housings, vehicle door handles, luggage racks, coffee-grinder parts and ornamental fixtures.

3. Mangnesium Alloys:


Magnesium alloys contain 3 to 10% aluminium, 1 to 3.5% zinc and 0.4% manganese.

Dow metal (an alloy of magnesium) contains 91% magnesium and 9% aluminium.

Electron Metal (a trade name of magnesium) base alloy contains 4% zinc and small percentages of copper, iron and silicon.


(i) The tensile strength of magnesium alloys is not high, averaging between 90 and 180 MN/m2. This can be improved to 220-260 MN/m2 when the alloys is in sheet form, and to 290-350 MN/m2 when forged or extruded.

(ii) Resistance to shock is increased by heat treatment after casting- heating to temperature between 330°C and 4150°C, followed by cooling in air.

(iii) Owing to the fierceness with which magnesium burns, a certain fire risk is bound to exist when machining the alloy.

(iv) On exposure to the atmosphere, magnesium alloys develop a dark oxide film which resists corrosion. To afford increased protection, and to provide a suitable base for paint or varnish, it is usual to subject the parts to chrome pickling process.

(v) Their weight is only two thirds that of aluminium and a quarter of that of steel.

(vi) Magnesium alloys (Dow metal) can be forged, welded and drawn in wires.


Alloys of aluminium and magnesium are called light alloys.

4. Nickel Alloys:

The important nickel alloys are- Iconol, Monel metal, NIchrome Brightray allo, Manganese nickel.

1. Iconol:


Ni = 75%, Cr = 15%, Fe = 9%


(i) It can be cast, forged, rolled and cold drawn.

(ii) It can be forged at 1000-1300°C but is brittle between 650°C and 950°C.

(iii) It has high corrosion resistance at ordinary and high temperature. Its tensile strength is 500 MN/m2 and brinell hardness 160.

(iv) Melting point = 1395°C; specific gravity = 8.55.

(v) Brinell hardness is about 160.

(vi) It can be soft soldered as the ordinary tin smiths solder using a neutral zinc chloride solution as a flux.

(vii) It can be welded by the oxyacetylene and metallic arc methods without difficulty.


1. It is used for making springs which have to stand high temperatures and are exposed to corrosion.

2. It is also used for exhaust manifolds (manifold is the main pipe which carries the explosive mixture from the carburetor to the cylinders of an internal combustion engine) of aircraft engines.

2. Monel Metal:


Monel metal can said to be two-thirds nickel, one third copper with small percentage of the elements iron, silicon, manganese and carbon. A number of different grades are- “K” Monel metal contains 66% nickel, 29% copper and 2.75% aluminium. “A” Monel metal contains 67% nickel and has no aluminium. This is a free machining alloy of slightly lower strength than the “K” type. Several grades contain manganese upto about 2%.


(i) Monel metal is superior to brass or bronze in resisting corrosion and in retaining its strength at high temperatures.

(ii) It is magnetic at ordinary temperatures when rolled, becoming nonmagnetic on heating to 100-150° C and regaining its magnetism on cooling.

(iii) Its mechanical properties are improved by cold working.

(iv) Addition of elements like aluminium and beryllium makes the alloy amenable to heat treatment.

(v) It can be welded but requires a very technique owing to its peculiar flow properties. It must be hammered after the deposition of each bead, to disperse the internal stresses set up in cooling.

(vi) It does not corrode under atmospheric conditions, even in air conditions of industrial centres.

(vii) It is only slightly attacked by acetic, citric and tartaric acids.


1. Owing to its excellent corrosion resistance properties, it is widely used for parts of water-pumps, propellers, domestic water storage tanks and parts subjected to high temperatures, such as internal combustion engines, valve seatings particularly in light alloy cylinder-heads.

2. It is also used for making turbine blades and chemical food handling plant.

3. Nichrome:


Ni = 60%, Cr = 15% and Fe = 20%


(i) It is practically non-corrosive.

(ii) It can withstand high temperatures without oxidation.

(iii) Alloyed with cast iron, it increases resistance of the latter to corrosion and heat as well as to wear.


It is used in making electrical resistance wire for electric furnaces and heating elements.

5. Brightray Alloys:

These are nickel-chromium alloys. They are highly heat resistant. Brightray contains Ni = 80%, Cr = 20%. It can be used for temperature upto 1150°C. Brightray H contains a small percentage of aluminium and can be used upto 1250°C.

6. Bearing or Antifriction Alloys:

A bearing alloy should have the following characteristics:

1. Good wearing quality.

2. Low co-efficient of friction.

3. High thermal conductivity.

4. High melting point.

5. Good casting qualities.

6. Ability to withstand continuous bearing pressure and impact.

7. Ability to work satisfactorily at the rubbing speed at which it is required to run.

8. Low shrinkage after casting.

9. Desired plasticity under the load it is called upon to bear.

10. Economy in cost.

11. Non-corrosive property.

Bearing Bronzes:

The description of typical bearing bronzes is given below:

1. Hard Bearing Bronze:


Cu = 85%. Sn = 15%


(i) Its tensile strength is 220 MN/m2.

(ii) It has Brinell hardness 100.

(iii) Elongation in 5 cm length is 2%.


It is used for heavy compressive loads, locomotive slide valves, bearings for turntables etc.

2. Phosphor Bronze:


Cu = 89%; Sn = 11%.


(i) Tensile strength is 280 MN/m2

(ii) It has Brinell hardness 100.

(iii) Elongation in 5 cm length is 4%.


It is widely employed for heavy loading.

3. Admiralty Gun Metal:


Cu = 88%, Sn = 10%, Pb = 2%


(i) Tensile strength is 270 MN/m2.

(ii) Brinell hardness is 65.

(iii) Elongation in 5 cm length is 4%.


It is used for general casting purposes, specially to resist marine corrosion, suitable for bearing when lubrication is good.

4. Lead Bronze:


Cu = 80%, Sn = 10%, Pb = 10%.


(i) Tensile strength is 230 MN/m2

(ii) Brinell hardness is 65.

(iii) Elongation in 5 cm length is 15%.


It has good antifriction properties and is used where lubrication is doubtful.

5. White Metals:

These metals are copper-lead alloys and are generally employed for heavy duty bearings.

6. Babbit Metal:

It is a white metal bearing alloy. The term now covers a range of alloys of similar characteristics but varying composition.

The exact composition of Babbit metal is not known, although it contained the following constituents in approximately the following proportions- Tin = 89.2%; copper = 3.8%; antimony = 7.0%.

A metal of this composition possesses excellent antifriction properties, but is expensive owing to high tin content.

A cheaper Babbit which is suitable for bearings subjected to moderate pressure is made up as follows- Tin = 59.5% minimum; copper = 2.25 to 3.75%; antimony = 9.5 to 11.5%;, lead = 26% maximum; iron = 0.08% maximum; bismuth = 0.08% maximum.

Babbit metal possesses a number of advantages as a bearing metal which are-

1. Soft enough to allow high-spots to be smoothed down in use.

2. It possesses sufficient mechanical strength for normal uses.

3. It is easy to cast and to scrap to a good lift.

4. Should a bearing overheat, the Babbit lining will melt and prevent the bearing from seizing up.

The performance of the metal is dependent upon the way in which it is manufactured, whether from ingots, melted and poured into pockets in the bearing concerned, or cast in position by centrifugal action derived from a special machine designed to minimise blow-hole formation.

7. Cadmium Silver Bearing Alloy:

It contains- Cadmium = 97.6%, copper = 1.9%, and silver = 0.5%. These bearings are used for loads upto 14.5 MN/m2.

8. Beryllium Capper Bearing:

It contains 97.5% copper and 2.25% beryllium.

It has been used as a hard bearing metal in place of phosphor bronze, its wear resistance being five times that of phosphor bronze.

Beryllium copper possesses a film forming and self-lubricating property which makes it more suitable as a bearing metal.

9. Graphite Bearing Metals:

A type of bearing metal sometimes known as spongy bearing bronze has resulted from investigations into the effect of graphite upon certain alloys. These metals contain graphite uniformly distributed throughout their composition, and when used for bearings they are therefore, self-lubricating.

Such bearings are applicable to non-accessible slow running machinery, both marine and stationary.


Porous bearings are produced by powder metallurgy. Powders of copper, tin and graphite are sintered, and then passed through a sizing die to the correct dimensions. The metal, thus produced is of a porous nature capable of holding upto one-third of its volume of oil. A pressure on the bearing surface, or a temperature rise, will cause the oil to exude, so that lubrication is ensured continuously and automatically where it is needed.