Materials Engineering

1. Copper and its alloys
By Asegid Tadesse
Wollega University, Ethiopia

2. Ferrous Nonferrous
 Iron is the principal constituent, such as
steels and cast iron.
 Consumed in large quantities because of
their wide range of mechanical properties,
ease of fabrication and economical to
produce.
 Nonferrous metals and alloys don’t contain
iron as a principal ingredient. But may contain
small percentages.
 High cost due to extraction and production.
 Not magnetic and are usually more resistant to
corrosion than ferrous metals.
 Limitations include:
• Relatively high density (gm/cm3):
• Iron (7.87), steel (7.8)
• Comparable low electrical
conductivity.
• Susceptibility to corrosion in
some environments.
 Preferred over ferrous metals due to:
• Light weight (gm/cm3).
Al (2.7), Mg (1.74), Ti (4.54), Cu (8.96),
Zn (7.13), Ni (8.89), Pb (11.36), Ag (10.49),
Au (19.32).
• Stiffness-strength to weight ratio
• Oxidation resistance
• Corrosion resistance
• Biocompatibility
• Thermal/electrical conductivity
 These metals are “all purpose” alloys  Used for applications, where properties of
ferrous metals are inadequate.
Metal alloys: Metal alloys, by virtue of composition, grouped into two as ferrous and nonferrous.
Introduction

3. Application Examples
Structural Aluminum, beryllium, and titanium
Engineering (light metals) lithium, magnesium, potassium, and sodium
also have.
High thermal and electrical
conductivity
Nickel and lead have widespread
applications as does copper
Coatings, electrical Cadmium, tin, and zinc
Electrical and jewelry. Gold, silver, and platinum, the precious
metals
Refractory metals (those with
melting points above 2000
degrees Celsius)
columbium, titanium, tungsten, vanadium,
and zirconium
Introduction
3
Nonferrous metals: Application

4. Aluminum
Chromium
Copper Lead
Manganese
Nickel Silver
Titanium
Vanadium
Cadmium
Cobalt Gold
Magnesium
Molybdenum
Platinum
Tin
Tungsten
Zinc
Metals Alloys
• Brass (copper + zinc)
• Tin bronze (copper + tin)
• Aluminum bronze ( copper + aluminum)
• Cupro-nickel alloys ( copper + nickel)
• Aluminum alloys
• Magnesium alloys
• Zinc-based die casting alloys
• Tin-lead alloys
Nonferrous metals
Introduction
Classification of nonferrous metals:
 Classified as nonferrous metals and nonferrous alloys.
 Classification of nonferrous alloys is either according to the base metal or
according to some specific characteristics that a group of alloy share.
4

5. Copper and its alloys:
 Produced by a pyrometallurgical (high temperature) process.
 Copper based alloys:
• Have higher densities than steels.
• Have specific strength values typically less than that of aluminum or
magnesium alloys.
• Better resistance to fatigue, creep and wear than the light weight
aluminum and magnesium alloys.
• Many of them have excellent ductility, corrosion resistance, electrical
and thermal conductivity, and most can easily be joined or fabricated
into useful shapes.
• Applications: electrical components (such as wire), pumps, valves,
plumbing parts, may be unusually be used to produce an appropriate
decorative color
Copper and its alloys
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6. Copper and its alloys:
 Unalloyed (pure) copper:
• Pure copper is red.
• It is so soft and ductile. Thus, difficult to machine.
• It has almost unlimited capacity to be cold worked.
• Highly resistance to corrosion in diverse environments such as the
ambient atmosphere, sea water, and some industrial chemicals.
 When alloyed:
• Mechanical and corrosion resistance properties of copper may be
improved by alloying.
• Alloys possess a desired combination of physical properties which
has been utilized in a variety of applications since antiquity.
Copper and its alloys
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7. Copper and its alloys:
 Most copper alloys can’t be hardened or strengthened by heat treating procedures. Thus,
either cold working or solid-solution alloying must be utilized to improve these
mechanical properties.
 Cold working:
• Increase both tensile strength and yield strength.
• For most coppers and copper alloys, tensile strength of hardest cold-worked temper
is approximately twice than that of the annealed temper.
• For the same alloys, the yield strength of the hardest cold worked temper may
be as much as five to six times that of the annealed temper.
 Hot working:
• Is commonly used for alloys that remain ductile above the recrystallization
temperature.
• It permits more extensive changes in shape than cold working, so that a single
operation can replace a sequence of forming and annealing operations
Copper and its alloys
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8. Brass:
 Brass is the most common copper alloys are the brasses for which zinc, a
Substitutional impurity, is the predominant alloying element.
 Zinc additions to copper produce a yellow color.
 Common brasses:
• Yellow, naval, and cartridge brass, muntz metal, and gilding metal.
 Applications:
• Costume jewelry, cartridge castings, automotive radiators,
instruments, electronic packaging and coins.
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9. Bronze:
 Are alloys of copper containing tin and other elements including
aluminum, silicon and nickel. .
 Are somewhat stronger than brasses, yet still have a high degree of
corrosion resistance. Thus, these alloys are used when good tensile
properties are needed in addition to corrosion resistance.
 Magnesium bronze: a high strength alloy containing magnesium as well
as zinc for solid solution strengthening.
 Tin bronzes:
 Often called phosphor bronzes.
 May contain up to 10% Sn and remain single phase.
 The phase diagram predicts the alloy will contain the compound,
Cu3Sn.
Copper and its alloys
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10. Six families of alloys depending on alloying:
 Coppers
• This family is essentially commercially pure copper which contains
less than about 0.7% total impurities.
 Dilute copper alloys
• These copper alloys contain small amounts of various alloying elements
that modify one or more of the basic properties of copper.
 Brasses (copper, zinc, lead)
• Copper-zinc alloys
• Alloy brasses include: copper-lead alloys, copper-zinc alloys with
titanium and aluminum
 Bronzes (copper, tin, silicon, aluminum):
Copper-tin alloys, copper-aluminum alloys, copper-silicon alloys, copper-
beryllium alloys
 Nickel alloys (copper, nickel, tin):
 Copper nickels
• Copperonickel (Cu-Ni) alloys, nickel silver (Cu-Ni-Zn) alloys
Copper and its alloys
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11. Two families of alloys depending on strength:
 Solid solution strengthened alloys:
• Most compatible alloying elements with copper are those that form solid-solution
fields.
• Copper based alloys containing large quantities of alloying elements may remain
single phase.
• These include all elements forming useful alloy families (Zn, Sn, Al, Si).
• Example: copper-zinc, copper-tin, copper-aluminum, and copper-beryllium.
• The mechanical properties increase as the zinc content increases.
• Tin bronze may contain up to 10% Sn and remain single phase.
• Aluminum bronze and silicon bronze alloys containing less than about 9% Al or
less than 3% Si are also single phase.
• These alloys have good forming characteristics and often selected for their good
strength and excellent toughness.
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Mechanical

12. Copper and its alloys
 Age-hardenable alloys:
• Age hardening produces very high strengths, but is limited to
those few copper alloys in which the solubility of the
alloying element decreases sharply with decreasing
temperature.
• The beryllium coppers, zirconium copper, chromium copper,
copper nickel phosphorous alloys and copper nickel silicon
alloys.
• Copper based alloys displaying an age hardening response
include: zirconium-copper, chromium-copper, and beryllium
copper.

13. Beryllium coppers:
 Are the most common heat-treatable copper alloys.
 These alloys possess remarkable combination of properties.
 Tensile strengths are as high as 1400 Mpa and excellent electrical and
corrosion and wear resistance properties when properly lubricated.
 May be cast, hot worked, or cold worked. High strengths are attained
by precipitation-hardening heat treatments.
 Because of the beryllium (1 to2.5 wt%) additions, these alloys are costly.
 Are used for high strength, high stiffness (springs and fine wires), and non-
sparking qualities (for tools to be used near flammable gases and liquids).
 Applications: Jet air craft landing gear bearings and bushings, springs,
surgical and dental instruments.
Copper and its alloys
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14. The Cu-Al phase diagram:
• Copper-aluminum alloys are also called aluminum bronzes.
• It is the α solid solution of aluminum in copper which produces
ductile, cold-working alloys which can be rolled into sheets and
drawn into wires.
• At about 10% Al, duplex alloys consisting of α+β phases are produced
above 5650C.
• Below 5650C, duplex alloys α+γ2 are produced.
• The γ2 phase is a hard intermetallic compound Cu9Al4. thus alloys
containing this phase are unsuitable for cold working, but are
excellent for casting.
• More, reading materials.
Copper and its alloys
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15. The Cu-Al phase diagram
9.4
11.8
15.6
5650C
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16. The Cu-Zn phase diagram:
 The copper-zinc or brass alloys with less than 40% Zn form single-
phase solid solutions of zinc in copper.
 This phase is the α-phase (FCC crystal structure).
 The α-brasses are relatively soft, ductile, and easily cold worked.
 Brass alloys having a higher Zn content contain both α and β’ phases at
room temperature.
 The β’ phase has an ordered BCC crystal structure and is harder and
stronger than the α phase; consequently, α+β’ alloys are generally hot
worked.
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17. The Cu-Zn phase diagram
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18. Lead-copper alloys:
• The lead forms a monotectic reaction with copper and produces tiny
lead spheres as the last liquid to solidify.
• The lead improves machining characteristics.
• Utilization of lead-copper alloys has a major environmental impact.
Thus lead free alloys have been developed.
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19. Copper and its alloys
Composition, property and application: Selected copper alloys
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20. Composition, property and application: Selected copper alloys
Copper and its alloys
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21. Applications:
 Cu (pure form or tough pitch copper):
• Electrical wires and water pipes.
 Cu-30Zn (Brass):
• Zn is the main Substitutional impurities.
• Cartridges, auto-radiator, musical instruments, coins, boiler fittings,
electrical components.
• 70/30 = Cartridge brass (350-600 MPa UTS): Condenser tube, Sheet
fabrication.
• 60/40 = Muntz metal (400-850 MPa): Hot working and casting: Valves,
marine propellers.
• 50/50 = Brazing alloys (small addition of Sn, Mn and Al).
 Cu-10 to 30Sn (Bronze): Sn, Al, Si, Ni.
• Stronger than brasses with high degree of corrosion resistance.
• Bearings, hard wires, and springs (Phosphor bronze).
• Imitation gold (Al Bronze ~ strength of steel).
• Propellers, coinage.
Copper and its alloys

22.  Cu-30Ni (Cupronickel):
• Nickel additions to copper produce a silver color.
• German silver (70/30, 80/20, 75/25) coinage, condenser tube.
• Monel metal (70/30 + small Fe).
• High strength and corrosion resistance.
• Chemical & food processing plants, turbine blades, corrosion
resistance bolts, screws & nails

23. Effect of alloying element on properties of copper :
 The best way to increase the electrical and thermal
conductivity of copper is to decrease the impurity levels.
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24. Effect of temperature on the softening of copper alloys:
Copper and its alloys
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25. Yield and tensile strength of copper, brass and steel:
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26. THANK YOU