Alloy steels contain alloying elements added to carbon steel to improve properties. Low alloy steels contain up to 8% alloying elements while high alloy steels contain more than 8%. Alloying elements like manganese, chromium, nickel, and molybdenum increase strength and hardness. Tool steels are specially formulated carbon and alloy steels selected for hardness, heat resistance, and ability to hold an edge at high temperatures. Common types include water hardening W grades, and cold working grades O and A which can be oil or air hardened respectively.

1. Ferrous and Non Ferrous metals
Limitations of plain carbon steels
 Cannot be strengthened above 690 MN/m2 without loss of
ductility and impact resistance.
 The depth of hardening is limited.
 Must be quenched very rapidly to obtain a fully martenstic
structure, leading to the possibility of quench distortion and
cracking.
 Have poor impact resistance at low temperatures.
 Alloy steels containing a number of alloying elements have
been developed to overcome these deficiencies.

2. ALLOY STEELS
A homogeneous mixture or solid solution of two or more
metals, the atoms of one replacing or occupying interstitial
positions between the atoms of the other.
The principal alloying elements used are :
Manganese (Mn), nickel (Ni), chromium (Cr), molybdenum(Mo),
tungsten (W), vanadium (V), cobalt (Co), silicon (Si), boron (B),
copper (Cu), titanium (Ti) and niobium (Nb).
 Low Alloy steel (Alloying elements<=8%)
 High Alloy steel (Alloying elements>8%)

3. Effect of alloying elements
Carbon
 Carbon is the primary hardening element in steel.
 Hardness and tensile strength increases as carbon content increases.
 Ductility and weld-ability decreases with increasing carbon.
Manganese
 Beneficial to surface quality especially in resulfurized steels.
 Manganese contributes to strength and hardness, but less than
carbon.
 The increase in strength is dependent upon the carbon content.
 Increasing the manganese content decreases ductility and weldability,
but less than carbon.

4. Phosphorus
 Increases strength and hardness and decreases ductility and notch
impact toughness of steel.
 Higher phosphorus is specified in low-carbon free-machining steels
to improve machinability.
Sulphur
 Decreases ductility and notch impact toughness especially in the
transverse direction.
 Weldability decreases with increasing sulphur content. Sulphur is
found primarily in the form of sulfide inclusions.
 The only exception is free-machining steels, where sulphur is
added to improve machinability.

5. Silicon
 Is one of the principal deoxidizers used in steelmaking.
 Silicon is less effective than manganese in increasing as-rolled
strength and hardness.
 Increases magnetic properties
Copper
 Is beneficial to atmospheric corrosion resistance when present in
amounts exceeding 0.20.
 Copper (0.10% to 0.50%) in significant amounts is detrimental to
hot-working steels.
 Copper negatively affects forge welding, but does not seriously
affect arc or oxyacetylene welding.
 Copper can be detrimental to surface quality.

6. Lead
 Is virtually insoluble in liquid or solid steel.
 Lead is sometimes added to carbon and alloy steels by means of
mechanical dispersion during pouring to improve the machinability.
Boron
 Is added to improve hardenability.
 Boron-treated steels are produced to a range of 0.0005 to 0.003%.
 Improves machinablity and cold forming capacity
Chromium
 Is commonly added to steel to increase corrosion resistance and
oxidation resistance
 Also increases the hardenability, and improves high-temperature
strength.

7. Nickel
 Is a ferrite strengthener.
 Nickel does not form carbides in steel.
 It remains in solution in ferrite, strengthening and toughening the
ferrite phase.
 Nickel increases the hardenability and impact strength of steels.
Molybdenum
 Increases the hardenability of steel.
 Molybdenum may produce secondary hardening during the
tempering of quenched steels.
 It enhances the creep strength of low-alloy steels at elevated
temperatures
Aluminum
 Is widely used as a deoxidizer.
 Aluminum can control austenite grain growth in reheated steels and
is therefore added to control grain size.
 Aluminum is the most effective alloy in controlling grain growth
prior to quenching.

8. Titanium, zirconium, and vanadium
 Are also valuable grain growth inhibitors, but there carbides are
difficult to dissolve into solution in austenite.
 Vanadium increases the yield strength and the tensile strength of
carbon steel.

9. High strength low alloy steels (HSLA)
 Not hardened by heat treatments
 Yield strength (289-482) Mpa , tensile strength (414 – 621) Mpa.
 Microstructure will be in the form of ferrite-pearlite
 Low carbon content (less than 0.2 %) , 1.0 % Mn and less than 0.5% of
other alloying elements
 Provides increased strength to weight ratio.
 Especially preferable for thinner sections.
 Superior in weldablity, formablity, toughness & strength compared to plain
carbon steels.
 They can be annealed, normalized, or stress relieved.
Applications
 Trucks, construction equipment, off-highway vehicles, mining
equipment and other heavy-duty vehicles use HSLA sheets or plates
for chassis components, buckets, all type Structural works.
 Applications such as offshore oil and gas rigs, single-pole power-
Transmission towers, railroad cars, and ship construction.

10. High alloy steels
Stainless steel
 In metallurgy stainless is defined as an iron-carbon alloy with a
minimum of 11.5 wt% chromium content.
 Stainless steels are High alloy steels and have superior corrosion
resistance because they contain relatively large amount of chromium
Selecting a Stainless Steel
 Corrosion resistance
 Magnetic properties
 Resistance to oxidation and sulfidation
 Ambient strength
 Ductility
 Resistance to abrasion and erosion
 Toughness
 Elevated temperature strength
 Cryogenic strength
 Thermal conductivity
 Electrical resistivity etc

11. Types of Stainless steel
 Austenitic grades
 Ferrite grades
 Martensitic
 Precipitation-hardening martensitic stainless steels
 Duplex stainless steels
Austenitic grades –Features
 Compostion:0.15% carbon;16% -26%Chromium ,nickel-8-24 %
Magnese-15%
 Retain austenitic structure
 Austenitic steels have Face Centered Cubic structure.
 Non magnetic in the annealed condition and can be hardened
only by cold working.
 Possess excellent cryogenic properties and high temperature
strength.

12. Ferritic grades
 Highly corrosion-resistant, but less durable than austenitic grades.
 Compostion-less than 0.2%carbon and 16 – 20 % chromium and
very little nickel, molybdenum; some, aluminum or titanium.
 Common ferritic grades include 18Cr-2Mo, 26Cr-1Mo, 29Cr-4Mo,
and 29Cr-4Mo-2Ni.
 Ferritic grades are chromium containing alloys with bcc crystal
structure
 The ferritic alloys are Ferro magnetic
 They can have good ductility and formablity, but high temperature
strength are relatively poor compared to austenitic grades

13. Martensitic grades
 Compostion:1.2% carbon;12% -18 %Chromium
 Martensitic stainless steels are not as corrosion-resistant as the other two
classes
 Extremely strong and tough, as well as highly machinable.
 Heat treatable.
 Body centered cubic crystal structure in the hardened condition.
 Resistant to corrosion only in the mild environment
 Excess carbides present to increase wear resistance or to maintain
cutting edges
Precipitation –hardening martenstic stainless steels
 Precipitation hardening stainless steels are chromium-nickel alloys.
 PH most common grade;17%chromium 4%nickel.
 Precipitation hardened to get higher strengths than the other martensitic
grades
 Precipitation-hardening stainless steels may be either austenitic or
martensitic in the annealed condition.

14. Duplex stainless steels
 Duplex stainless steels are a mixture of BCC ferrite and FCC
austenite crystal structures.
 The percentage in each phase is a dependent on the composition and
heat treatment(mostly 40 – 60 %).
 Most Duplex stainless steels are intended to contain around equal
amounts of ferrite and austenite phases in the annealed condition.
 The primary alloying elements are chromium and nickel.
 Duplex stainless steels generally have similar corrosion resistance to
austenitic alloys.
 Duplex stainless steels also generally have greater tensile and yield
strengths, but poorer toughness than austenitic stainless steels.
Stainless steel grades
200 Series—austenitic chromium-nickel-manganese alloys
300 Series—austenitic chromium-nickel alloys
400 Series—ferritic and martensitic chromium alloys
500 Series—heat-resisting chromium alloys
600 Series—martensitic precipitation hardening alloys

16. Tool steels
 Tool steel refers to a variety of carbon and alloy steels that are
particularly well-suited to be made into tools .
 Tool steels contain more alloying elements than normal alloy steels.
 Hardness, resistance to abrasion, ability to hold a cutting edge,
and/or their resistance to deformation at elevated temperatures are
the major features.

17. Types of tool steels

18. Defining property AISI grade Significant
characteristics
Water-hardening W
Cold-working
O Oil-hardening
A Air-hardening; medium alloy
D High carbon; high chromium
Shock resisting S Tungsten base
High speed
T Tungsten base
M Molybdenum base
Hot-working H
H1-H19: chromium base
H20-H39: tungsten base
H40-H59: molybdenum base
Plastic mold P
Special purpose
L Low alloy
F Carbon tungsten

19. Water-hardening grades
 W-grade tool steel is water quenched tool .
 W-grade steel is essentially high carbon
 This type of tool steel is the most commonly used tool steel because
of its low cost compared to other tool steels.
 They work well for small parts and applications where high
temperatures are not encountered; above 150 °C (300 °F) it begins to
soften to a noticeable degree.
 Hardenability is low so W-grade tool steels must be quenched in
water. These steels are rather brittle.
Typical applications for various carbon compositions are:
 0.60—0.75% carbon: machine parts, chisels, setscrews
 0.76—0.90% carbon: forging dies, hammers, and sledges.
 0.91—1.10% carbon: drills, cutters, and shear blades.
 1.11—1.30% carbon: small drills, lathe tools, razor blades

20. Cold-working grades
Grade-O refers to oil hardening and grade-A refers to air hardening.
 The toughness of O-grade and A-grade tool steels are increased by
alloying with silicon, Manganese, Silicon, Chromium.
 These tool steels are used on larger parts
 More alloying elements are used in these steels, as compared to
water-hardening grades.
 These alloys increase the steels' hardenability, and thus require a less
severe quenching process. These steels are also less likely to crack.
 D-grade tool steels contain between 10% and 18% chromium and
carbon from 1.50- 2.35 %. These steels retain their hardness up to a
temperature of 425 °C (800 °F). Common applications for these
grade of tool steel is forging dies, die-casting die blocks, and
drawing dies.

21. Shock resisting grades
 S-grade tool steel are designed to resist shock at both low and high
temperatures.
 A low carbon content is required for the necessary toughness
(approximately 0.5% carbon).
High speed grades
 T-grade and M-grade tool steels are used for cutting tools where
strength and hardness must be retained at temperatures up to or
exceeding 760 °C (1400 °F).
 M-grade tool steels were developed to reduce the amount of tungsten
and chromium required.
 T (also known as 18-4-1) is a common T-grade alloy. Its composition
is 0.7% carbon, 18% tungsten, 4% chromium, and 1% vanadium.

22. Hot-working grades
 H-grade tool steels were developed for strength and hardness during
prolonged exposure to elevated temperatures.
 All of these tool steels use a substantial amount of carbide forming
alloys.
 H1 to H19 are based on a chromium content of 5%;
 H20 to H39 are based on a tungsten content of 9 to 18% and a
chromium content of 3 to 4%;
 H40 to H59 are molybdenum based.
Special purpose grades
 P-grade tool steel is short for plastic mold steels. They are designed to
meet the requirements of zinc die casting and plastic injection molding
dies.
 L-grade tool steel is short for low alloy special purpose tool steel. L6 is
extremely tough.
 F-grade tool steel is water hardened by substantially more wear resistant
than W-grade tool steel.

23.  Maraging Steels
 Maraging steel is essentially free of carbon, which distinguishes it from
most other types of steel. The result is a steel which Possesses high
strength and toughness.
 A special class of low carbon ultra-high strength steels which derive
their strength not from carbon but from precipitation of inter-metallic
compounds.
 Maraging steels are carbon free iron-nickel alloys with additions of
cobalt, molybdenum, titanium and aluminium.
 Cobalt is added in percentages up to 12% to accelerate the precipitation
reactions.
 The term maraging is derived from the strengthening mechanism,
which is transforming the alloy to martensite with subsequent age
hardening .
Applications
 Aerospace, e.g. undercarriage parts and wing fitting, Tooling &
machinery, e.g. extrusion press rams and mandrels in tube production,
gears and fasteners.
 They are suited to engine component applications such as crankshafts,

24. Non ferrous alloys
The more common non-ferrous materials are the following
metallic elements and their alloys:
 Copper
 Aluminium
 Magnesium
 Lead
 Nickel
 Tin
 Zinc
 Cobalt etc.

25. COPPER
The main grades of raw copper used for cast copper base alloys are
 High conductivity copper (electrolytic) having min 99.9% Cu. The
oxygen content may be of the order 0.40%, Pb and Fe less than 0.005% Ag
0002% and Bi less than 0.001%. Electrolytic copper is used for electrical
purposes.
 Deoxidized copper having min 99.85% Cu, less than 0.05%As, 003% Fe
and 0.003% Bi. Other elements may be of the 0.05% P 0.01% Pb, 0.10% Ni,
0.003% and 0.005% Ag and Sb respectively.
 Arsenical deoxidized copper having 0.4% As, 0.04% P and remaining
copper. It is used for welded vessels and tanks.
 Arsenical touch pitch copper containing 0.4% As, 0.065% oxygen,0.002%
Pb, 0.15% Ni 0.006% Ag, 0.01% Sb and less than 0.005% BI, less than
0.020% Fe and remaining copper.
 Oxygen free copper contains 0.005% Pb, 0.001% Ni, 0.001% Ag
and less than 0.0005% and 0.001 % Fe and Bi respectively. It is melted and
cast in non-oxidising atmosphere

26. Properties and applications of Copper :
Properties
 Excellent resistance to corrosion.
 Non-magnetic properties.
 Easy to work, it is ductile and malleable.
 Moderate to high hardness and strength.
 High thermal and electrical conductivity. .
 It can be easily polished, plated and possesses a pleasing appearance.
 Resistance to fatigue, abrasion and corrosion.
 It can be soldered, brazed or welded.
 Very good machinability. .
 Ease of forming alloys with other elements like Zn, Sn, AI, Pb, Si, Ni,
etc.
Applications
 (i ) Electrical parts,
 (ii) Heat exchangers,
 (iii) Screw machine products,
 (iv) For making various copper alloys, such as brass and bronze,

27. Copper Alloys
 High strength and corrosion resistance, a combination desirable for
marine applications.
 Possess excellent corrosion resistance, electrical and thermal
conductivities and formability.
 High wearing properties, hardness.
 Some copper alloys are selected for decorative applications because
of appearance.
 Elements such as aluminium, zinc, tin, beryllium, nickel, silicon, lead
etc., form alloys with copper.
Classification of Copper alloys :
High copper alloys - contains 96.0 to 99.3% copper.
 Possess enhanced mechanical properties due to the addition of small
amounts of alloying elements such as chromium, zirconium,
beryllium and cadmium. A few typical high copper alloys are:
 (i) Cu,1% Cd (ii) Cu, 0.8% Cr (iii) Cu, 0.12-0.30% Zr
(iv) Cu, 1.5-2.0% Be
 Used for electrical and electronic components resistance welding
electrodes, wire conductors, diaphragms .

28. BRASSES
 Brasses contain zinc as the principle alloying element.
Brasses are subdivided into three groups;
 (i) Cu-Zn alloys,
 (ii) Cu-Pb-Zn alloys or leaded brasses, and
 (iii) Cu-Zn-Sn alloys or tin brasses.
 Zinc in the brass increases ductility along with strength.
 Brass has high resistance to corrosion and is easily machinable also acts as
good bearing material.
 Brass possesses greater strength than copper, however, it has lower thermal
and electrical conductivity.
Various types of brasses are discussed below:
 (1) Gilding metal
 Range from 5% to 15% Zn( balance Cu) and possess shades of colour from
the red of copper to a brassy yellow.
 They are supplied mainly in the form of sheet strip and wire for jewellery
and many other decorative purposes.
 Like copper, gilding metal is hardened and strengthened by cold work.
 Gilding metal is used making coins, medals, tokens, fuse caps etc.

29. (2) Cartridge brass -contains 70% Cu and 30% Zn.
 In the fully annealed condition it has a tensile strength of over 300 N/mm2.
 Greater % elongation and tensile strength
 cold deformation in presses and by spinning or other means,
 Used for cupped articles like the caps of electric lamp bulbs, door furniture
etc.
 Cartridge brass work hardens when deformed in the cold, and
must be annealed if many successive operations are to be performed.
(3) Admiralty brass
 Admiralty brass contains Cu 71%, Zn 28%, and Sn 1%.
 The small amount of tin added to brass improves its resistance to certain
types of corrosion.
 Used exacting conditions of marine condensers.
 widely used for the tubes and other parts of condensers cooled by fresh
water and for many other purposes.
 For such applications, the modern alloy contains about 0.04%. Arsenic,
which improves resistance to a penetrative form of corrosion known as
dezincification.

30. (4) Aluminium brass -contains 76% Cu, 22% Zn and 2% Al ,a little arsenic is
added to inhibit dezincification.
 In contact with sea water, a protective film builds up on the
surface of this alloy in the early stages of corrosion and prevents
further attack.
 Moreover, if the film is damaged, by the abrasive action of sand particles,
for instance, it is self-healing.
(5) Basis brass -contains copper 61.5-64%, the remainder being zinc.
 Basis brass is used for press work where a relatively cheap material is
required,
 The main commercial forms are sheet, strip and wire.
(6) Muntz metal or yellow metal - contains 60% of copper and 40% of Zn
 Essentially a hot working material.
 It is manufactured in the form of hot rolled plate, and hot rolled rod or
extruded sections in a great variety of shapes and sizes.
 Yellow metal is frequently used as a brazing alloy for steel.
 Other applications of muntz metal are as: Ship sheathing ,Perforated metal
,Valve stems ,Condenser tubes ,Architectural work etc.

31. (7)Leaded 60 : 40 brass - is the chief material fed to automatic lathe and
similar machines, usually in the form of extruded bar .
 Lead is added to Cu-Zn alloy to promote machinability,
 The lead content ranges from about 0:5% to as much as 3.5%.
 60:40 brass, tends to improve the weldability, ductility and impact strength.
 used for: Keys , Lock-parts, Gears, Clock parts, Valve parts ,Pipe unions.
(8) Nava1 brass -contains Cu 60%, Zn 39.25% and Sn 0.75%.
 The purpose of tin is to Improve the resistance to corrosion.
 Used for structural applications and for forgings, especially in cases where
contact with sea water
 Naval brass is obtainable as hot-rolled plate particularly for
marine condenser plates, and in the form of extruded rod for the
production of machined or hot forged components.
 Other applications of naval brass are: Propeller shafts ,Valve stems ,Pump
impellers etc.
(9) Admiralty brass -contains 71 % Cu, 28% Zn, and 1% Sn.
 It is used for decorative and architectural applications, screw machine
products, heat exchanger components, pump impellers

32. BRONZE
 Bronze is basically an alloy of copper, tin and elements other than nickel or zinc .
 Bronze possesses superior mechanical properties and corrosion resistance than
brass.
 Bronze is comparatively hard and it resists surface wear.
 Bronze can be shaped or rolled into wire, rod and sheets.
Types of bronzes
(i) Phosphor Bronze -deoxidized with phosphorus during the refining process and
hence are known as phosphor bronze.
 The amount of phosphorus may range from a trace to about 0.35% or even higher in
some special grades.
 In amounts greater than 1.0% phosphorus causes excessive brittleness
 A phosphor bronze containing approximately 4% each of tin, lead and zinc has
excellent free-cutting characteristics.
 Standard Phosphor bronze for bearing applications contains 90% Cu, 10% Sn (min),
and 0.5% P (min).
 It has a tensile strength of 220-280 N/mm2
 Phosphor bronze for gears contains 88% Cu, 12% Sn, 0.3% (max) Zn, 0.50% (max)
Pb and 0.15% (min) P.
 It has a tensile strength of 220-310 N/mm2. This alloy is also utilised for general
bearings, where its rigidity is of advantage.

33.  Leaded phosphor bronze contains 87% Cu, 7.5% Sn, 2.0% (max) Zn, 3.5% Pb, 0.3%
(min) P and 1.0% (max) Ni.
 It has a tensile strength of 250 N/mm2
 This material is satisfactory for many bearing applications.
Properties of phosphor bronze
 (a) has high strength and toughness
 (b) is resistant to corrosion
 (c) has good load bearing capacity, and
 (d) has low coefficient of friction.
Applications
 (a) bearing applications
 (b) making pump parts, linings, springs, diaphragms, gears, clutch discs, bellows etc.
(ii) Aluminium bronzes – contains Cu -89-91,% Al, 6-8% ,Fe 1.5 -3.5% , Sn 0.35 % Mn
1%(max)
Properties of Aluminium bronzes :
Good strength ,High corrosion resistance ,Good heat resistance ,Good cold working
properties, etc,
Used in-Bearings, Valve seats ,Gears ,Propellers ,Slide valves, Cams ,Imitation jewellery,
Pump parts etc.
(iii) Silicon bronzes – contains Si 1-4%, Fe 0.5-1.0% ,Mn 0.25-1.25% ,and balance Cu
 Lead when added as 0.5% improves machinability.
Used in: Bearings ,Roll mill sleepers, Screwdown nuts ,Boiler parts ,Die cast parts etc.

34. GUN METAL
 Gun metal is an alloy of copper, tin and zinc.
 Zinc cleans the metal and increases its fluidity.
 A small amount of lead may be added to improve cast ability and machinability.
Types
Admirality gun metal contains 10% Sn, 2% Zn, 1.5% max Ni and balance Cu.
 It has tensile strength of 260-340 N/mm2.
 It is used for pumps, valves and miscellaneous castings.
Leaded gun metal contains 7% Sn, 2.25% Zn, 0.3% Pb, 5.5 and balance copper.
It has a tensile strength of 430-480 N/rr.m2.
Nickel gun metal contains 5% Sn, 5% Zn, 5% Pb, 2.0% max Ni.
It has a tensile strength of 200-270 N/mm2.
This is among the most widely used grades, particularly where high pressure is
required.
In general gun metal is used for
Bearings ,Steam pipe fittings ,Hydraulic valves and gears, etc

35. Cupronickel or copper-nickel
 Is an alloy of copper that contains nickel and strengthening elements, such
as iron and manganese.
 Cupronickel is highly resistant to corrosion in seawater.
 It is used for piping, heat exchangers and condensers in seawater systems as
well as marine hardware, and sometimes for the propellers, crankshafts etc.
 A more familiar common use is in silver-coloured modern circulation
coins. A typical mix is 75% copper, 25% nickel, and a trace amount of
manganese.
 It is used in thermocouples, and the 55% copper/45% nickel alloy
constantan is used to make resistors, thermocouples, and rheostats
 Monel metal is a nickel-copper alloy, containing minimum 63% nickel and
31.5 percent copper, with small amounts of iron, manganese, carbon, and
silicon.
 Stronger than pure nickel,
 Monel alloys are resistant to corrosion by many agents, including rapidly
flowing seawater. They can be fabricated readily by hot- and cold-working,
machining, and welding.

36. BEARING MATERIALS
 Bearings support moving parts, such as shafts and spindles, of a machine or
mechanism.
 Bearings may be classified as
 RoIling contact (i.e., Ball and roller) bearings.
 Plain bearings.
Copper-based alloys
 Bronze covers a large number of copper alloys with varying percentages of
Sn, Zn and Pb.
 Bronze is one of the oldest known bearing materials.
 Typical compositions of bearing bronze arc:
 Cu-80% ,Sn -10% ,Pb -10%
 Cu-85% ,Sn -15%
 Bronze (10 to 14% tin remainder copper) is used in the machine and engine
industry for bearing bushes made from thin walled drawn tubes.
 Copper-based alloys are employed for making bearings required to resist
heavier pressures such as in railways.

37. Babbitt metal
 Babbitt metal is most commonly used as a thin surface
layer in a complex, multi-metal structure
 Babbitt metal is characterized by its resistance to galling.
 Babbitt metal is soft and easily damaged
 Its structure is made up of small hard crystals dispersed in
a softer metal, which makes it a metal matrix composite.
 As the bearing wears, the softer metal erodes creating
paths for lubricant between the hard high spots that
provide the actual bearing surface.
 When tin is used as the softer metal, friction causes the
tin to melt and function as a lubricant, protecting the
bearing from wear when other lubricants are absent.

38. ALUMINIUM AND ITS ALLOYS
 Aluminium is a silvery white metal and it has the following characteristics:
 (i) It is a light metal, with a density about a third that of steel or brass.
 (ii) Aluminium is a very good conductor of electricity.
 (iii)Aluminium has a higher resistance to corrosion than other metals, but film of
oxide may forms on its surface.
 (iv) Aluminium is a good conductor of heat.
 (v) Aluminium is very ductile.
 . (vi) Aluminium is non-magnetic.
 (vii) Melting point of pure aluminium is about 6500C
 Although pure aluminium is not particularly strong, it forms strength alloys with
other metals such as CU, Cr, Ni, Fe, Zn, Mn, Si and Mg.
 (i) Some of these aluminium alloys are more than 4 times strong as the same weight
of mild steel.
 (ii) They are malleable and ductile.
 (iii)They exhibit toughness and become stronger at temperaturebelow the ordinary
atmospheric range.
 (iv)They do not work well at temperatures of the order of 300-4OOOC.
 (v) Aluminium and its alloys can be (a) Cast (b) Forged (c) Welded (d) Extruded (e)
Rolled, etc.

39. Uses of AI and Al-alloys
 (i) Transportation industry-structural frame-work, engine parts, trim
and decorative features, hardware, doors, window frames, tanks,
furnishing and fittings,trains, trucks, buses, automobile cars and
aeroplanes use many component parts made up of aluminium alloys.
 (ii) Overhead conductors and heat exchanger parts.
 (iii) In food industry, aluminium alloys find applications as food
preparation equipments(pans, etc.), refrigeration, storage containers,
bakery equipment, shipping containers, etc.
 (iv) In architectural field, aluminium alloys find uses such as window
farmes, doors hardware, roofing, coping sills, railings, fasteners,
lighting fixture solar shading, grills, etc.
 (v) Cryogenic applications.
 (vi) As heavy duty structures such as travelling cranes, hoists,
conveyor supports, bridges, etc.
 (vii) In process industries, parts made up of aluminium and its alloys
are used to handle organic chemicals, petrochemicals and drugs.
Tanks, pipes, heat exchangers, gratings, smoke-stacks, precipitators,
centrifugal valves, fittings, etc. are produced from aluminium alloys.

40.  Types of aluminium alloys Aluminium alloys
 Al-Mn
 Al-Mg
 Al-Mg-Mn
 Al-Mg-Si
 Al-CU-Mg
 Al-Cu-Si
 Al-CU-Mg-Pb
 Al-Mg-Si-Pb
 Al-Zn-Mg-Cu
Aluminium alloys can be classified as follows:
(a) Wrought alloys
(b) Cast alloys
(c) Heat-treatable alloys
(d) Non-heat-treatable alloys.

41. CERAMICS
 Ceramics are inorganic non metallic materials which are formed by
the action of heat. The most important of these were the traditional
clays, made into pottery, bricks, tiles and the like, along with
cements and glass.
Mechanical properties
 Ceramic materials are usually ionic or covalent bonded materials,
and can be crystalline or amorphous.
 Has less tensile strength
 High hardness due to brittility
 High compressive strength
 Poor toughness
 wear-resistant
 thermal insulators
 electrical insulators
 nonmagnetic
 oxidation resistant
 prone to thermal shock and
 chemically stable.

42. Classification of ceramics
 Ceramics can also be classified into
 Oxides : Alumina, zirconia .
 Non-oxides: Carbides, borides, nitrides, silicides .
Carbides
 It is a compound of carbon with a less electronegative element. For
example Fe3C (cementite), is formed in steels to improve their
properties.
 Examples
 Calcium carbide ,Silicon carbide (SiC), Tungsten carbide, Cementite
,Boron carbide, Tantalum carbide ,Titanium carbide ,Silicon carbide
Silicon carbide (SiC) (carbarundum)
 It is a compound of silicon and carbon bonded together to
form ceramics.

43. Properties of carbides
 High strength
 Low thermal expansion
 High thermal conductivity
 High hardness
 High elastic modulus
 Excellent thermal shock resistance
 Superior chemical inertness

44. Applications of SiC
 Fixed and moving turbine components
 Suction box covers
 Seals, bearings
 Ball valve parts
 Hot gas flow liners
 Heat exchangers
 Semiconductor process equipment
 Abrasives
 Disc brake
 Diesel particulate filter
 Cutting tools
 Coarse to fine grit sandpapers

45. Aluminum Oxide, (Al2O3) Alumina
 Aluminium oxide is of aluminium with the chemical formula Al2O3.
Being very hard, it is used as an abrasive. Having a high melting
point, it is used as a refractory material.
Key Properties
 Hard, wear-resistant
 Excellent dielectric properties
 Resists strong acid and alkali attack at elevated temperatures
 Good thermal conductivity
 Excellent size and shape capability
 High strength and stiffness
 Aluminium oxide is an electrical insulator
 But has a relatively high thermal conductivity (40 W/m K).
 In its most commonly occurring crystalline form, called corundum or
α-aluminium oxide
 As a component in cutting tools.[3]

46. Applications
 Gas laser tubes
 Wear pads
 Seal rings
 High temperature electrical insulators
 High voltage insulators
 Furnace liner tubes
 Thread and wire guides
 Electronic substrates
 Abrasion resistant tube and elbow liners
 Laboratory instrument tubes and sample holders
 Instrumentation parts for thermal property test machines
 Grinding media
 Over 90% of which is used in the manufacture of aluminium metal.
 Health and medical applications include it as a material in hip replacements,
 It is widely used as a coarse or fine abrasive, including as a much less expensive
substitute for industrial diamond.
 Many types of sandpaper use aluminium oxide crystals.
 Aluminium oxide is widely used in the fabrication of superconducting devices,

47. Partially stabilized Zirconia (PSZ) (ZrO2)
Tensile strength higher than alumina
Toughness and fracture toughness is better than other ceramics
High elavated temperature strength
Applications of ZrO2
 Precision ball valve balls and seats
 High density ball and pebble mill grinding media
 Rollers and guides for metal tube forming
 Thread and wire guides
 Hot metal extrusion dies
 Deep well down-hole valves and seats
 Powder compacting dies
 Marine pump seals and shaft guides
 Oxygen sensors
 High temperature induction furnace susceptors
 Fuel cell membranes
 Electric furnace heaters over 2000°C in oxidizing atmospheres

48. NITRIDES
 Nitride is a compound of nitrogen with a less electronegative element.
 Silicon nitride (Si3N4) is a hard, solid substance, that can be obtained by
direct reaction between silicon and nitrogen .
 For machining of steel, it is usually coated by titanium nitride .
 Cubic boron nitride is used in grinding wheel in the form of abrasive.
APPLICATIONS
The largest market for silicon nitride components is in reciprocating (diesel and
spark ignited) engines for combustion components and wear parts.
 glow plugs for faster start-up
 Precombustion chambers
 turbocharger
 exhaust gas control valve for increased acceleration.
 fixtures in induction heating and resistance welding exploit the
electrical insulation, wear resistance, low thermal conductivity and
thermal shock resistance of the material.
 Nozzles, thermocouple sheats and melting crucibles for handling
molten aluminium, zinc, tin and lead alloys.
 Arc welding nozzles for high strength, electrical resistance and thermal
shock resistance of the material.

49. Sialon
 It is a silicon nitride ceramic with a small percentage of aluminum oxide
added.
 It is highly thermal shock resistant, strong, and is not wet or corroded by
aluminum, brass, bronze, and other common industrial metals.
Properties
 Excellent thermal shock resistance
 Not wetted or corroded by nonferrous metals
 High strength
 Good fracture toughness
 Good high temperature strength
 Low thermal expansion
 Good oxidation resistance
 Retain tensile strength upto 1400OC
Application
 Thermocouple protection tubes for nonferrous metal melting
 Machining nickel based alloys
 Immersion heater and burner tubes
 Degassing and injector tubes in nonferrous metals
 Metal feed tubes in aluminum die casting
 Welding and brazing fixtures and pins

50. COMPOSITE MATERIALS
 Composite is a mixture of two or more distinct constituent or phases
 Both constituents have to be present in reasonable property ,say 5%.
 The constituent that is continuous and is often but not always
,present in the greater quantity in the composite is termed as matrix.
 The second constituent is referred to as the reinforcing phase or
reinforcement as it reinforces the mechanical properties of matrix.
The reinforcement is harder, stronger and stiffer than matrix in most
causes.
Functions of Matrix Material:
 It takes the load and transfers it to the reinforcement.
 It binds or holds the reinforcement and protects the same from
mechanical or chemical damage that might occur by abrasion of their
surface (in particular with fibers).
 It also separates the individual fibers and prevents brittle cracks from
passing completely across the section of the composite.
Functions of Reinforcing Material:
 The major load on the composite is carried by the reinforcing phase.

51. Advantages of composite materials
 High strength to weight ratio
 High stiffness
 Low density
 High young’s modulus & tensile strength
 Increase in the toughness
Types of composites
 Metal Matrix composites
 Ceramic Matrix composites
 Polymer Matrix composites
Metal Matrix composites(MMC)
 Matrix - Aluminium, Copper, Nickel based alloys, Iron etc
 Reinforcement – Carbon, Silicon Carbide(SiC),Aluminium
oxide(Al2O3), Tungsten carbide etc.

52. Applications of Al/SiC MMC:
Automotive -Reciprocating and static engine components, braking
systems
Aerospace -Struts, undercarriage, guided weapons, satellites
Rail Engineering -Engine and braking components
Military -Gun barrel overwraps, missiles (aerofoils and fins, bodies
and blast pipes),military , diesel components.
Electronic -Substrates and packaging, thermal management,
racking, power sources and storage
Marine -Propellers, impellers, pressurized hulls, marine diesel
components
Industrial -Reciprocating and high speed machinery, precision
equipment
Sport/Leisure -Rackets, cycles and frames, motor racing, golf clubs

53. Ceramic Matrix composites(CMC):
 In case of CMC ceramic materials are used as matrix. Some of the ceramic
materials used are
 Silicon carbide
 Alumina
 Glass ceramics
 Carbon
Advantages:
 Co efficient of thermal expansion of ceramics is low
 Thermal and electrical conductivity is less than MMC
 CMC can withstand high temperature and can provide high strength than
MMC
Disadvantages:
 CMC can withstand very high temperature only if the
reinforcement is a high temperature withstanding material
 After processing the thermal stress in MMC can be relieved
from plastic deformation , whereas it is not possible in CMC

54.  Types of CMCs:
 Alumina matrix composites
 SiC whisker reinforced CMC-Used for cutting tools and
manufacturing industries
 Zirconia toughened alumina
 Glass ceramic matrix composites
 Carbon-carbon composites
Applications of CMCs:
Applications:
 Aerospace -After burners, brakes, heat shields, nozzles
 Automobile - Brakes
 Manufacturing- Thermal insulation, cutting tools, wire
drawing dies
 Medical - Fixation plates

55. POLYMER MATRIX COMPOSITES:
Types of polymers:
 Thermosets
 Thermo plastics-Crystalline and Non-crystalline
 Rubber
Advantages:
 Low strength
 Low strength than MMC & CMC
 Low fracture toughness
Disadvantage:
 Low working temperature
 Low coefficient of thermal expansion
 Dimensional instability
Commercial PMCs:
 Fibre reinforced epoxies
 Carbon-fiber reinforced plastic or CFRP
 Glass-fiber reinforced plastic or GFRP (also GRP).
 Aramid fibre reinforced plastic

56. Applications:
 Industrial -Solar collectors, Electrostatic precipitation plates, Fan
blades, Water tanks
 Recreational - Television antennas, Snow mobiles
 Construction -Seating, bath tabs, roof sections, bus shelters
 Aerospace -Wing ribs, helicopter blades, landing gears, cockpit hatch
covers, escape doors
 Automobile -Crash members, leaf springs, car bodies
 Electrical -Panels, housings, switch gear
 Chemical -Pipes, tanks, pressure vessels, hoppers, valves, pumps