List of Metals and their Alloys | Material Engineering

Here is a list of metals and their alloys.

An alloy is a substance that has metallic properties and is composed of two or more chemical elements, of which, at least one is a metal. Basically, alloying is done to give strength to metal as the alloying element occupies interstitial space, which create compressive and tensile strength depending on the position of alloying element leads to strengthen the metal.

Alloy may be homogeneous or mixture. Alloy having single phase is called homogeneous alloy. If it is mixture, it will have combinations of several phases and it is termed as heterogeneous alloy.

Purpose of Alloying:

(i) Increase in hardenability.

(ii) Improve strength at ordinary temperature.

(iii) Improve mechanical properties at high or low temperature.

(iv) Improves toughness, wear resistance, corrosion resistance and magnetic properties.

1. Copper and Its Alloys:

Copper has many applications, both as pure metal and an alloy base metal. It is malleable and ductile metal and can be easily rolled, drawn or forged. The tensile strength and hardness of copper can be improved by cold working although the ductility is reduced. Conversely, the annealing can improve the ductility at the expense of the tensile strength and hardness. The importance of copper is due mainly to its very high coefficient of electrical conductivity.

It has very good thermal conductivity and corrosion resistance. The impurities present in copper can have serious effects upon the properties of the metal. The electrical conductivity is reduced by 25% due to the presence of 0.04% phosphorus. Addition of 0.5% lead or tellurium imparts free-cutting properties to copper. Hydrogen is soluble in solid copper. Addition of 1% Cd improves the strength when used in telephone wires, but has minimal effect on the electrical conductivity.

Copper is rapidly attacked by sulphuric acid, hydrochloric acid, nitric acid, ammonia, sodium hydroxide, potassium hydroxide and amines. Copper can be safely used with sulphurous acid (in paper industry), neutral salts, e.g., sodium chloride, hydrocarbons, alcohols, acetic acid aldehydes, ketones, ethers, lactic and tannic acid. Upto 0.5% arsenic added to copper to use in locomotive.

Alloys of Copper:

I. BRASS:

Alloy of Cu & Zn having high corrosion resistance and good machinability. It acts, as good bearing material. Brass may joined by soft soldering using tin based solders with an antimony content below 5% with decrease in Zn content, risk of cracking drawing timing and soldering reduced.

Example of Brass (With Composition and Application):

i. Muntz Metal (60% Cu + 40% Zn):

It has high tensile strength, suitable for hot working by rolling, stamping, extruding

Used in pump parts, marine fittings, valves.

ii. Cartridge Brass (70% Cu + 30% Zn):

Useful for cold working.

Used for tubes sheets and cold press work.

iii. Admiralty Brass (70% Cu + 29% Zn + 1% Sn):

High corrosion and abrasion resistance. Used in condenser tubes and marine work.

iv. Red Brass (5% to 20% Zn alloys):

Freedom from seasonal cracking. Used in rivets, pipe end connections etc.

v. Delta Metal (55% Cu + 41% Zn + 2% Pb + 2% Fe):

Used in marine engines, screw propeller, chemical, hydraulic and mining plants.

Brass also used in manufacturing of evaporators in sugar industries due to corrosion resistance and heat conductivity. Conductivity of brass is lesser than Cu.

II. Bronze:

It is a Cu – Sn alloy. Tin varies from 2 – 12%. These are “harder” than brass.

Bronze is formed by “casting”, brass is formed by “working”.

i. Phosphor Bronze (94.8% Cu + 5% Sn + 0.2% P):

Used in springs, welding Rods, diaphragms, fuse clips. Bellows, clutch discs.

ii. Gun Metal (83% Cu + 10%, Sn + 2% Zn):

High corrosion resistance.

Used in marine work, valves, water fittings.

iii. Engineers Bronze (88% Cu + 10% + 2% Zn):

Steam fittings, Engine parts and hydraulic machinery.

iv. Aluminium Bronze (85% Cu + 4% Fe +11% Al):

Used in Bearings, gears, worms, busing, valve seats, pickling hooks.

2. Aluminium and Its Alloys:

Aluminum cannot be purified by blowing air through it, as in the case of iron. This treatment would oxidise the aluminum and leave behind the impurities. Therefore the ore must be purified before being electrolysed and this involves an expensive chemical process. Aluminum has a great affinity for oxygen, its corrosion-resistance is relatively, high.

This is due to the dense impervious film of oxide which forms on the surface of the metal and protects it from further oxidation. The high affinity of aluminum for oxygen also makes it useful as de-oxidant in steels and also in the thermite process of welding.

Aluminum used as a metallurgical material are its low relative density and its high affinity for oxygen.

Since its relative density is only about one-third that of steel, or of a copper-base alloy, it is used, when alloyed with small amounts of other elements, for castings in aero, automobile and constructional engineering.

Alloying and heat-treatment can produce alloys of aluminum which are stronger than steel, so that the use of aluminum alloys is further extended to stress-bearing members in both aero-engine and airframe. Pure aluminum is relatively soft and weak (it has a tensile strength of about 90 N/mm² in the annealed condition), so that for most other engineering purposes it is used in the alloyed condition.

Alloys of Aluminum:

One of the chief-defects to which aluminum alloys are prone to porosity due to gases dissolved during the melting process.

Molten aluminum will dissolve considerable amounts of hydrogen if, for any reason, this is present in the furnace atmosphere. When the metal is cast and starts to solidify the solubility of hydrogen diminishes almost to zero, so that tiny bubbles of gas are formed in the partly solid metal. These cannot escape and give rise to “pinhole” porosity.

The defect is eliminated by treating the molten metal before casting with a suitable flux, or by bubbling nitrogen or chlorine through the melt. As a substitute for chlorine, which is a poisonous gas, tablets of the organic compound hexachlorophene can be used.

Aluminum alloys are used in both the cast and wrought conditions. Mechanical properties of them, both cast and wrought, can be improved by the process known as “precipitation-hardening”.

Duralumin:

It has high machinability.

It is strong as steel but has 1/3^rd of its weight so it is used to fabricate parts of aircrafts and automobiles.

It can be heat treated to increase its strength upto 4300 Kg/cm².

New generation Al – Li alloys are used in aircraft and aerospace industries in cryogenic tank structures.

These materials have relatively low density, high specific modules and excellent fatigue and low temperature toughness.

3. Nickel and Its Alloys:

It is crystalline, non-ferrous, ferromagnetic metal of silvery-white colour.

Its hardness matches and compared with the hardness of soft steel but ductility is less than that. The thermal conductivity and electrical conductivity are poor as compared to copper.

It possesses excellent corrosion resistant against many alkalis and acids. Nickel can be easily joined and hot or cold worked.

It can be used for both anode and cathodes.

Nickel is often used as a cladding on mild steel (NiCad), providing both strength and corrosion resistance.

It is capable of high quality polishing, thereby provides luster to the products on which it is polished.

It is reasonably malleable and can also be rolled provided the carbon content is in small amount (upto 0.5% or less)

It is resistant to acidic attacks, but dissolves readily in nitric acid.

Its melting point and specific gravity are 1453°C and 8.9 respectively.

Nickel Alloys:

i. Hastelloy:

These are Nickel and Molybdenum alloys with Fe, Cr, Cu, Al present in certain proportion.

These are high strength and high temperature alloys with a very high creep resistance.

ii. Monel Hetal (63% Ni + 30% Cu + Fe + Mn + Si + C):

It is not affected by sea water or atmosphere.

It is highly resistant to the corroding effect of alkalis and acids.

It is used in evaporators (chemical plants), pump impellers for corrosive liquids, pickling plants and drying plants.

Monel metal filter cloth is used extensively, paints and varnishes are made of Monel metal.

iii. K-Monel Metal:

When (Al) is added to monel metal the utility of K – monel is that it can be made hard by heat treatment retaining corrosive resisting properties of monel metal.

It can be either hot rolled or cold worked.

It used in valves and seats in pumps, valves and seats of air bottles used for diesel engines.

Blades, used in paper making industry, impulse blades for steam turbines, radio instruments due to its non-magnetic nature.

iv. German Silver (65% Cu + 25% Zn + 10% Ni):

It is very resistant to corrosion used in rivets, screws, fasteners, nameplates, hollow wares etc.

v. Nickel-Fe Alloys:

As nickel content increases in iron, magnetic properties decreases and reduce to almost negligible at Ni (28 – 30%). The coefficient of expansion of alloys is practically zero at Ni (25 – 35%), this property used for making precision instruments.

vi. Invar:

Very low coefficient of thermal expansion or may be zero, so it issued in provision equipment. Thus used in clock pendulums, measuring tapes and thermostats.

vi. Nichrome (Ni + Cr) alloy (80% Ni + 20% Cr):

Resistance to oxidation increases by the addition of chromium.

Also as the Cr content increases electrical resistance of the alloy increases. At 20% Cr the alloy has electrical resistant 11 times that of ordinary nickel.

It is used in making heating element, coils for furnaces sheet and cast plates for furnace bottom, thermocouple sheets.

viii. Inconel (80% Ni + 14% Cr + 6% Fe):

High mechanical properties coupled with corrosion and heat resisting properties. It is highly resistant to oxidation upto 900° C.

It can be welded, brazed, solderd, pressed etc. tensile strength may reach upto 1400 MPa.

It is used in manufacturing of machinery for food processing industries, especially milk and milk products, electronic parts, gas turbine parts, heat treating Equipment etc.

4. Super Alloys:

It is also known as heat resistant or high temperature alloys.

Major applications are gas turbines and jet engines, rocket engines, nuclear, petrochemical industries. For such an application mechanical antiquity is critical.

In this regard density is important. Consideration because the centrifugal stresses are diminished in rotating member when density reduced.

These material are classified on the basis of dominant metal in alloy.

These alloys are resistant to creep and thermal corrosion.

Most super alloys have maximum service temperature of about 1000° C.

There are 3 types of super alloys:

(a) Iron Base Super alloys: contain (32% – 67% Fe + 15% – 22% Cr + 9 – 38% Ni)

(b) Cobalt Base Super alloys: (35 – 65% Co) + (upto 35% Ni) + (19 – 30% Cr). These alloy specially retain their strength at high temperature due to cobalt.

(c) Nickel Base Super alloys: Most common type proportion of Nickel varies from (38 – 76%) + (< 27% Cr) + (< 20% Co).

5. Tin Alloys:

1. Solder:

These are three types:

2. Bearing Materials – Babbitt Metals:

Tin Based Babbitt: 90% Sn + 4.5% Cr + 5% Antimony + 0.5% Pb

Lead Based Babbitt: 84% Pb + 6% Sn + 0.5% Cu + 9.5% Antimony.

These Babbitt metals are bearing materials that are used as cast liners with bronze or steel backing. Babbitt is preferred to bronze for high speeds and fluctuating loads.

These have excellent conformability and embedabillity.

Tin based Babbitt have better corrosion resistance as compared to lead based Babbitt.

For low speed operations under high pressures bronzes are preferred upto 20% tin lead is added to bronze where lubrication is poor.

Aluminium bronze is another good material for bearing (Ni-Cd) compound acts as a hardening agent.

Latest is the metal flouro-plastic material where a thin porous bronze layer (0.3mm) is filled with a mixture of flouro plastic and molybdenum disulphide. This is an antifriction material.

6. Refractory Metals:

Metals with extremely high melting point. They are Niobium, Mo, W, Ta. Melting point rang from (2500 – 3400°). (W) has highest m.p of 3410° C.

These have high strength and hardness at very high temperature.

Used as alloying elements to steel for improving various properties.

Mo-alloy are used in extrusion dies, space vehicles, incandescent light filaments, x- ray tubes. W-alloys are in making welding electrodes. Tantalum alloys are immune to chemical attack in all environments below 150° C.

7. Zinc and Its Alloys:

Pure zinc is relatively soft and weak and is brittle at room temperature. It is therefore difficult to cold work, but can be easily rolled into sheets at temperatures between 100°C and 150°C.

In this form, it is used for battery cases and roofing and provides corrosion resistance due to the formation of a dense protective surface layer. Zinc is also used for sacrificial anodes to protect ship’s hulls and buried pipes.

A major use of zinc is in providing a coating, known as galvanising, for corrosion protection on ferrous materials.

Zinc Alloys:

The low melting point of zinc-based alloys makes them an excellent material for die-casting purposes, and so they can be cast in relatively inexpensive dies.

A small amount of aluminium on diffusing into solid solution with Zn lowers the melting temperature. Alloys used for die casting usually contain 4% Al, 1% to 2% Cu and the balance is zinc, producing a reasonably strong material.

8. Ferrous Alloys:

I. Carbon Steel:

Iron-carbon alloy that may contain appreciable amount of alloying elements. Carbon content is normally less than 1%. Plain carbon steels are alloys of iron and carbon where carbon does not exceed 1%, Manganese does not exceed 1.65% and copper and silicon does not exceed 0.60%.

They are classified as:

i. Low Carbon Steels:

Carbon content is generally less than 0.25%, and these are unresponsive to heat treatment intended to form martensite and strengthening is accomplished by cold working.

Microstructure consists of ferrite and pearlite constituents. These are soft, weak but ductile and tough and are least expensive to produce. They have wealdability better than all steel due to low Carbon Percentage.

Usages:

i. Automobile body structural shape such as I-beams, channels and angle irons etc.

i. Tin cans

ii. Medium Carbon Steels:

Carbon content between 0.25%C-0.65%C. These alloys can be heat treated by quenching and then tempering to improve mechanical properties. Microstructure is generally tempered martensite. These have low harden abilities and can be heat treated in only very thin section with very rapid quenching rate. These are stronger than low carbon steel but less ductile and tough.

Usages:

i. Railways wheels and trucks

ii. Gears

iii. Machine point

iv. Crankshaft

Designation:

Plain carbon steels initial digits start with (1 and 0). Last two digits gives carbon percentage.

For alloy steels initial digits are other than (1 and 0). Unified Numbering system (UNS) is used for indexing both ferrous and nonferrous alloys. It consists of a letter prefix followed by a 5 digit. Letter indicates family of metals to which alloy belongs. For medium carbon steels it is (G), for tool steel it is (T).

iii. High Carbon Steel:

Carbon content between (0.6%C-1.5%C). These are hardest and strongest, but ductility and toughness is lowest than plain carbon steel. These are most suitable for hardening.

These are wear resistant and capable of holding sharp cutting edge tool. Die steels are high carbon steels.

II. Low Alloy Steels:

Steels containing total alloy content upto 5% are called low alloy steels.

Categories of various low alloy steels are:

i. These are almost always used in a hardened and tempered condition

ii. The tools and dies steel are high carbon alloys usually containing chromic vanadium, tunguston and molybdenum.

III. Stainless Steels (or Corrosion Resistant Steels):

These are highly resistant to corrosion in variety of environments. Predominant alloying element is chromium, whose content of minimum 11% is required. These steels have good ductility and toughness at low temperature and high strength at elevated temperature. Chromium gives high corrosion resistance and because of this property, it is called as stainless steel.