Material science: Non-Ferrous metals and alloys

Communication Technologies
August 6, 2017
Material Science: Processing of Metals
August 8, 2017

1. Introduction

2. Aluminium

2.1 Aluminium alloys

a) Duralumin

b) Y-Alloy

c) Magnalium

d) Hindalium

3. Copper

3.1 Alloys of Copper

a) Brass

b) Bronze

4. Other metals

4.1 Lead

4.2 Tin

4.3 Zinc

4.4 Nickel

4.4.1 Alloys of Nickel

a) German silver

b) Monel metal

c) Nichrome

d) Inconel and incoloy

4.5 Magnesium

4.6 Vanadium

4.7 Antimony

4.8 Cadmium

4.9 Bearing Materials

4.10 Titanium alloys

4.11 Refractory metals

4.12 Noble metals

5. FAQs

 

1. Introduction

Non-ferrous metals are those which do not contain significant quantity of iron or iron as base metal. These metals possess low strength at high temperatures, generally suffer from hot shortness[FAD] and have more shrinkage than ferrous metals.

They are utilized in industry due to following advantages:

  • High corrosion resistance
  • Easy to fabricate, i.e., machining, casting, welding, forging and rolling
  • Possess very good thermal and electrical conductivity
  • Attractive colour and low density

But these metal are expensive than ferrous metals as they are not abundantly available

However different materials have distinct characteristics, and are used for specific purposes.

The various non-metals used in industry are: copper, aluminium, tin, lead, zinc, and nickel, etc., and their alloys.

2. Aluminium

Aluminium is white metal which is produced by electrical processes from clayey mineral known as bauxite. However, this aluminium ore bauxite is available in India in plenty and we have a thriving aluminium industry.

Properties:

  • These are characterized by low density, high thermal & electrical conductivities,
  • good corrosion resistant characteristics because of formation of Al2O3 protective layer.
  • As Al has FCC crystal structure, these alloys are ductile even at low temperatures and can be formed easily.
  • However, the great limitation of these alloys is their low melting point (660 ْC), which restricts their use at elevated temperatures.

Applications:

Aerospace: The absolute requirement for light structures, make aluminium and its alloys now more than ever the number one material in the sky.

Automotive: Chassis, bodies, engine blocks, radiators, hubcaps etc. because of its lightweight and corrosion resistance

Marine: Marine transport is increasing its use of aluminium by capitalizing on its two leading qualities: lightness and corrosion resistance. Advanced alloys have enabled the design of high-speed ships, by lightening hulls by 40% to 50% over steel.

Rail: Lighter structures, resistance and durability have made aluminium crucial to rail transport applications.

Packaging: Its lightness saves both on the material and the energy it takes to produce it. It is complete recyclability makes it reusable in the economic cycle.

Energy distribution: Aluminium’s low density combined with its excellent electrical conductivity make it a crucial material in the distribution of electricity.

Sports and leisure: sports equipment (hang gliders, ski poles, golf clubs, off-road bikes, scooters) and leisure products (trailers, camping, diving and mountaineering equipment).

2.1 Alloys of Aluminium

Aluminium may be alloyed with one or more alloying elements such as copper, manganese, magnesium, silicon and nickel.

What is the advantage of  alloy addition?

The addition of small quantities of alloying elements converts the soft and weak aluminium into hard and strong metal, while it retains its light weight.

The main alloys of aluminium are: Duralumin, Y-alloy, Magnalium and Hindalium which are discussed as follows

a) Duralumin

Composition:

  • This is a famous alloy of aluminium containing 4% copper, 0.5% manganese, 0.5% magnesium and a trace of iron with remainder as aluminium is known as duralumin.

Properties:

  • It possesses high strength comparable with mild steel and low specific gravity.
  • However, its corrosion resistance is much lower as compared with pure aluminium.
  • The strength of this alloy increases significantly when heat treated and allowed to age for 3 to 4 weeks, it will be hardened.
  • To improve upon the corrosion resistance of it, a thin film of aluminium is rolled on the duralumin sheets.

Applications:

  • These aluminium rolled sheets are known as Alclad by trade name and are widely used in aircraft industry.
  • Due to lightweight and high strength this alloy may be used in automobile industry.

b) Y-Alloy

It is also known as copper-aluminium alloy.

Composition:

  • The addition of copper to pure aluminium improves its strength and machinability.
  • Y-alloy contains 93% aluminium, 2% copper, 1% nickel and magnesium.

Properties:

  • This alloy is heat treated as well as age hardened just like duralumin.
  • A heat treatment of Y-alloy castings, consisting of quenching in boiling water from 510°C and then aging for 5 days develops very good mechanical characteristics in them.

Applications:

  • Since Y-alloy has better strength at elevated temperature than duralumin therefore it is much used in aircraft cylinder heads and piston.
  • It is also used in strip and sheet form.

c) Magnalium

  • It is produced by melting the aluminium and 2 to 10% magnesium in a vacuum and then cooling it in vacuum or under a pressure of 100 to 200 atmospheres.
  • About 1.75% copper is also added to it.

Applications:

  • Due to its light weight and good mechanical characteristics, it is mainly used for aircraft and automobile components.

d) Hindalium

  • It is an alloy of aluminium and magnesium with small quantity of chromium.
  • It is manufactured as rolled product in 16 gauge mainly used in manufacture of anodized utensils.

3. Copper

The crude form of copper extracted from its ores through series of processes contains 68% purity known as Blister copper. By electrolytic refining process, highly pure (99.9%) copper which is remelted and casted into suitable shapes.

Copper is a corrosion resistant metal of an attractive reddish brown colour.

Properties and Uses:

  • High Thermal Conductivity: Used in heat exchangers, heating vessels and appliances, etc.
  • High Electrical Conductivity: Used as electrical conductor in various shapes and forms for various applications.
  • Good Corrosion Resistance: Used for providing coating on steel prior to nickel and chromium plating
  • High Ductility: Can be easily cold worked, folded and spun. Requires annealing after cold working as it loses its ductility.

3.1 Alloys of Copper

Most copper alloys cannot be hardened or strengthened by heat-treating procedures. consequently, cold working and/or solid-solution alloying must be utilized to improve these mechanical properties.

  • Copper alloys are among the best conductors of heat and electricity and they have good corrosion resistance.

The common types of copper alloys are brasses and bronzes.

a) Brass

All brasses are basically alloys of copper and zinc.

Commercially there are two main varieties of brasses:

  1. Alpha brass:
    • Contains up to 36% Zn and rest copper for cold working.
  2. Alpha-Beta brass:
    • Contains 36 to 45% Zn and remainder is copper for hot working.

Effect of Zinc on Copper:

  • The tensile strength and ductility of brass both increase with increase in content of Zn up to 30% zinc.
  • With further increase in zinc content beyond 30%, the tensile strength continues to increase up to 45% of Zn, but ductility of brasses drops significantly.
  • β- phase is less ductile than α-phase but it is harder and stronger.

There are various types of brasses depending upon proportion of copper and zinc.

  • Fundamentally brass is a binary alloy of copper with as much as 50% zinc.
  • Various classes of brasses such as cartridge brass, Muntz Metal leaded brass, Admiralty brass, naval brass and nickel brass depending upon the proportion of copper and zinc plus third alloying metal are available for various uses.

Applications:

  • Brasses possess very good corrosion resistance and can be easily soldered.
  • Costume jewelry, cartridge casings, automotive radiators, musical instruments, electronic packaging, and coins.

b) Bronze

The alloy of copper and tin are usually termed bronzes.

  • The useful range of composition is 75 to 95% copper and remainder tin.
  • In general, it possesses superior mechanical properties and corrosion resistance to brass.

Properties:

  • The alloy can be easily cold rolled into wire, rods and sheets.
  • With increase in tin content, the strength of this alloy and its corrosion resistance increases. It is then known as hot working bronze.

Applications:

  • Bronze is generally utilized in hydraulic fittings, bearings, bushes, utensils, sheets, rods and many other stamped and drawn products.

The properties of bronzes are modified with different alloying elements as below

Phosphor bronze

When bronze contains phosphorus, it is known as phosphor bronze.

Properties:

  • The composition of the alloy varies according to whether it is to be forged, wrought or cast.

A common type of phosphor bronze has the following composition as per Indian standards.

  • Copper is 93.6%, tin is 9%, and phosphorus is 0.1 to 0.3%.
  • The alloy possesses good wearing qualities and high elasticity.
  • The alloy is resistant to saltwater corrosion.

Applications:

  • Cast phosphor bronze is utilized for production of bearings and gears.
  • Bearings of bronze contain 10% tin and small addition of lead.
  • This is also used in making gears, nuts, for machine lead screws, springs, pump parts, linings and many other such applications.

Gun metal

Composition:

  • Gun metal contains 2% zinc, 10% tin and 88% copper.

Properties:

  • Sometimes very small amount of lead is also added to improve castability and machinability.
  • The presence of zinc improve its fluidity.

Applications:

  • This bronze is used for bearing bushes, glands, pump valves and boiler fittings, etc.

Silicon bronze

Composition:

  • Silicon bronze has an average composition of 3% silicon, 1% manganese and rest copper.

Properties:

  • It possesses good general corrosion resistance of copper with higher strength and toughness.
  • It can be cast rolled, stamped, forged and pressed either hot or cold and can be welded by all the usual methods.

Applications:

  • Silicon bronze is widely utilized for parts of boilers, tanks, stoves or where high strength as well as corrosion resistance is required.

Bell metal

Composition:

  • This alloy contains 20 to 21% tin and rest copper.

Properties:

  • It is hard and resistant to surface wear.
  • It can be readily cast

Applications:

  • generally utilized for casting bells, gongs and utensils, etc.

Manganese Bronze

Composition:

It contains 55 to 60% copper, 40% zinc, with 3.5% manganese.

Properties:

  • This alloy is highly resistant to corrosion.
  • It is stronger and harder than phosphor bronze. It has poor response to cold working but can be easily hot worked.

Applications:

  • It is generally utilized for producing bushes, plungers, feed pumps and rods, etc.
  • Worm gears are frequently made of manganese bronze.

Muntz Metal

Composition:

  • 60% copper and 40% zinc.
  • Sometimes a small quantity of lead is also added.

Properties:

  • This alloy is stronger, harder and more ductile than normal brass.
  • While hot working between 700°C to 750, it responds excellently for process but does not respond to cold working.

Applications:

  • This alloy is utilized for a wide variety of small components of machines, bolts, rods, tubes, electrical equipment as well as ordnance works.
  • It is widely employed in producing such articles which are required to resist wear.

4. Other metals

4.1 Lead

Lead is the heaviest of the common metal. Lead is extracted from its ore known as galena. It is bluish grey in colour and dull lusture which goes very dull on exposure to air.

Properties and Uses:

  • Its specific gravity is 7.1(w.r.to water) and melting point is 360°C.
  • It is resistant to corrosion and many chemicals do not react with it (even acids).
  • It is soft, heavy and malleable, can be easily worked and shaped.
  • Lead is utilized as alloying element in producing solders and plumber’s solders.
  • It is alloyed with brass as well as steel to improve their machinability.
  • It is utilized in manufacturing of water pipes, coating for electrical cables, acid tanks and roof covering etc.

4.2 Tin

It is a brilliant white metal with yellowish tinge. Melting point of tin is 240°C

Properties and Uses:

(1) Tin is malleable and ductile, it can be rolled into very thin sheets.

(2) It is used for tinning of copper and brass utensils and copper wire before its conversion into cables.

(3) It is useful as a protective coating for iron and steel since it does corrode in dry or wet atmosphere.

(4) It is utilized for making important alloys such as fine solder and moisture proof packing with thin tin sheets.

4.3 Zinc

The chief ores of zinc are blende (ZnS) and calamine (ZnCO3).

Zinc is a fairly heavy, bluish-white metal principally utilized in view of its low cost, corrosion resistance and alloying characteristics. Melting point of zinc is 420°C and it boils at 940°C.

Properties and Uses:

  • High corrosion resistance: Widely used as protective coating on iron and steel. Coating may be provided by dip galvanizing or electroplating.
  • High fluidity and low melting point: Most suitable metal for pressure die casting generally in the form of alloy.
  • When rolled into sheets, zinc is utilized for roof covering and for providing a damp proof non-corrosive lining to containers.
  • The galvanized wires, nails, etc. are produced by galvanizing technique and zinc is also used in manufacture of brasses.

4.4 Nickel

About 85% of all nickel production is obtained from sulphide ores.

Properties and Uses:

  • Pure nickel is tough, silver coloured metal, harder than copper having some but less ductility but of about same strength.
  • It is plated on steel to provide a corrosion resistance surface or layer.
  • Widely used as an alloying element with steel. Higher proportions are advantageously added in the production of steel such as monel or inconel.
  • It possesses good resistance to both acids and alkalis regarding corrosion so widely utilized in food processing equipment.

4.4.1 Alloys of Nickel

a) German silver

Composition:

  • The composition of this alloy is 60% Cu, 30% Ni and 10% zinc.

Properties:

  • It displays silvery appearance and is very ductile and malleable.

Applications:

  • It is utilized for electrical contacts, casting of high quality valves, taps and costume jewellery. It is also used in producing electrical wires.

b) Monel metal

Composition:

  • It contains 68% Ni, 30% Cu, 1% iron and remainder small additions of Mn and other elements.

Properties:

  • It is corrosion resistant and possesses good mechanical properties and maintains them at elevated temperatures.

c) Nichrome

  • It is an alloy of nickel and chromium which is utilized as heat resistant electrical wire in electrical appliances such as furnaces, geysers and electric iron, etc.

d) Inconel and incoloy

  • These alloys principally contain, Ni, Cr, Fe, Mo, Ti and very small proportions of carbon.
  • These are used as high temperature alloys. Inconel does not respond to heat treatment.

4.5 Magnesium

Principal ores of magnesium are magnesite, carnallite and dolomite. Magnesium is extracted by electrolytic process.

Properties and Uses:

  • It is the lightest of all metals weighing around two-thirds of aluminium.
  • The tensile strength of cast metal is the same as that of ordinary cast aluminium, i.e., 90 MPa.
  • The tensile strength of rolled annealed magnesium is same as that of good quality cast iron.
  • Magnesium can be easily formed, drawn forged and machined with high accuracy. (5) In powdered form it is likely to burn, in that situation adequate fire protection measures should be strictly observed.
  • It’s castings are pressure tight and achieve good surface finish. Magnesium castings include motor car gearbox, differential housing and portable tools.

4.6 Vanadium

It occurs in conjunction with iron pyrite, free sulphur and carbonaceous matter.

Properties and Uses:

(1) It is silvery white in colour.

(2) Its specific gravity is 5.67.

(3) Its melting point is 1710°C.

(4) When heated to a suitable temperature it can be hammered into any shape or drawn into wires.

(5) It is used in manufacture of alloy steels.

(6) Vanadium forms non-ferrous alloys of copper and aluminium from which excellent castings can be produced.

4.7 Antimony

Chief ore of antimony is stibnite. To a small extent, antimony is obtained as a by-product in refining of other metals such as lead, copper silver and zinc.

Properties and Uses:

  • It is silvery white, hard, highly crystalline and so brittle that it may be readily powdered.
  • Its specific gravity is 6.63 and melting point is 630°C.
  • It is generally used as an alloying element with most of heavy metals.
  • Lead, tin and copper are the metals which are most commonly alloyed with antimony.

4.8 Cadmium

It is obtained commercially as a by-product in the metallurgy of zinc and to some extent of lead.

Properties and Uses:

  • White metal with bluish tinge, capable of taking a high polish.
  • Its specific gravity is 8.67 and melts at 321°C.
  • It is slightly harder than tin but softer than zinc.
  • It is malleable and ductile and can be readily rolled and drawn into wires.

It is chiefly utilized in antifriction alloys for bearings. It is also used as rust proof coating for iron and steel. Components of automobiles and refrigerator such as nuts, bolts and trimmings, locks and wire products are plated with it.

4.9 Bearing Materials

A bearing material should possess the following characteristics:

  • It should possess enough compressive strength to provide adequate load carrying capacity.
  • It should possess good plasticity to negate small variations in alignment and fitting.
  • Its wear resistance should be adequate to maintain a specified fit.
  • The coefficient of friction of the bearing material should be low to avoid excessive heating.

Some significant bearing metals are as follows:

Babbitt’s metal: It is utilized for production of heavy duty bearings. It is white in colour containing 88% tin, 8% antimony and 4% copper. It is a soft material with a low coefficient of thermal expansion.

4.10 Titanium alloys

  • Ti and its alloys are of relatively low density, high strength and have very high melting point.
  • At the same time they are easy to machine and forge.
  • However the major limitation is Ti’s chemical reactivity at high temperatures, which necessitated special techniques to extract. Thus these alloys are expensive.
  • They also possess excellent corrosion resistance in diverse atmospheres, and wear properties.

Applications:

  • Common applications include: space vehicles, airplane structures, surgical implants, and petroleum & chemical industries.

4.11 Refractory metals

  • These are metals of very high melting points. For example: Nb, Mo, W and Ta.
  • They also possess high strength and high elastic modulus.

Applications:

  • Space vehicles, x-ray tubes, welding electrodes, and where there is a need for corrosion resistance.

4.12 Noble metals

  • These are eight altogether: Ag, Au, Pt, Pa, Rh, Ru, Ir and Os.
  • All these possess some common properties such as: expensive, soft and ductile, oxidation resistant.

Ag, Au and Pt are used extensively in jewelry, alloys are Ag and Au are employed as dental restoration materials; Pt is used in chemical reactions as a catalyst and in thermocouples.

5. FAQs

1 Comment

  1. sunny says:

    sir/mam if possible please make a sequential naming of slides.

Leave a Reply

Your email address will not be published. Required fields are marked *