Cópia de Al alloys and Mg alloys

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Aluminium alloys and magnesium alloys
Al alloys:
Wrought Al alloys
Cast Al alloys
Precipitation hardening
Mg alloys:
Mg-Al-base alloys
Zr-containing alloys
Cast Mg alloys
Die casting
Al: 
atomic number 13
Atomic mass 26.982
Crystal structure fcc, a = 0.4041 nm
Melting poing 660ºC
Boiling point 2520 ºC
Density (r) 2.70 g/cm3
Elastic modulus E = 70GPa
Specific modulus E/r = 26
Applications:
Building and construction
Containers and packaging
Transportations
Electrical conductors
Machinery and equipment
Aluminium is the most abundant metallic 
element in the earth
O 45.2% Fe 5.8%
Si 27.2% Ca 5.06%
Al 8% Mg 2.77%
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major alloying element(s)
1xx.x pure Al
2xx.x Cu
3xx.x Si (Cu and/or Mg)
4xx.x Si
5xx.x Mg
7xx.x Zn
8xx.x Sn
9xx.x other element
Alloy designation - International alloy designation system (IADS)
Wrought Al alloys: Cast Al alloys
High purity Al: very low yield strength ~ 10 MPa, need to be alloyed
Al alloys
1. Wrought alloys (85%)
Non-heat-treatable Al alloys
High-purity Al alloys (1xxx series)
Al-Mn and Al-Mn-Mg alloys (3xxx series)
Al-Mg alloys (5xxxx series)
Heat-treatable alloys (respond to strengthening by heat treatment)
Al-Cu alloys (2xxxx series)
Al-Cu-Mg alloys (2xxxx series)
Al-Mg-Si alloys (6xxxx series)
Al-Zn-Mg and Al-Zn-Mg-Cu alloys (7xxxx series)
2. Cast alloys
Al-Si alloys
Al-Cu alloys
Al-Mg alloys
Al-Zn-Mg alloys 
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Wrought alloy productions:
Rolled plate (>6 mm in thickness)
Sheet (0.15 – 6 mm)
Foil (< 0.15 mm)
Extrusions
Tube
Rod bar and wire
• Internal wing structure on Boeing 767
• Aluminum is strengthened with precipitates formed
by alloying.
Adapted from Fig. 
11.26, Callister 7e.
(Fig. 11.26 is 
courtesy of G.H. 
Narayanan and A.G. 
Miller, Boeing 
Commercial Airplane 
Company.)
1.5mm
Precipitation Strengthening
Adapted from chapter-
opening photograph, 
Chapter 11, Callister 5e. 
(courtesy of G.H. 
Narayanan and A.G. 
Miller, Boeing Commercial 
Airplane Company.)
(p402 11.9)
•alloy 7150-T651 (6.2 Zn, 
2.3Cu, 2.3Mg, 0.12Zr, the 
balance Al)
•transition phase h’ and 
equilibrium phase h
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Al-Cu alloys
1. The maximum solubility of Cu in Al: 5.65 wt% at 548ºC
2. Eutectic reaction: L fi a (Al) + q (CuAl2)
3. Alloy of interest: Al-4.5wt% Cu
Slow cooling from 550ºC to RT
Coarse precipitates form at grain boundaries in an Al-Cu(4.5%) alloy when 
slowly cooled from the single phase a region to the two-phase (a+CuAl2) 
region. The isolated precipitates do little to affect alloy hardness. 
a+q
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Precipitation hardening (age-hardening)
By quenching and then reheating an Al-4.5Cu alloy, a fine dispersion of 
precipitates forms within the a grain. These precipitates are effective in 
hindering dislocation motion and, consequently, increasing alloy hardness 
(and strength). This process is known as precipitation hardening, or age 
hardening
a+q
overaging
Peak hardness
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GP zone
Coherent interface
1. GP (Guinier-Preston) zone formed at low 
temperature, 130ºC
2. transition phase q’’, 130ºC for long time, or < 
180ºC
3. equilibrium phase q (CuAl2), formed at T> 
190 ºC
(a) A supersaturated a solid solution, (Cu: substitutional atoms) (b) A transition 
q’’ precipitate phase, (c) the equilibrium q phase within the a-matrix phase.
f11_27_pg406
The precipitation hardening 
characteristics of a 2014 Al alloy
(0.9% Si, 4.4% Cu, 0.8% Mn, 
0.5%Mg) 
(a) Yield strength, 
(b) ductility (%EL)
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q’’ precipitates formed in a cast Al alloy. TEM. (a) bright field; 
(b) dark field I; (c) Dark field II
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How can age-hardening happen?
1. There is a decrease in solid solubility of the alloying 
element with decreasing temperature (see phase diagram).
2. The fine dispersed microstructure can be created during 
ageing
How to perform an age-hardening treatment
1. Solution treatment
Heated to a single-phase region, e.g. the a (Al) region 
2. Quenching
rapid cooled to room temperature to form a supersaturated solid 
solution (SSSS*)
3. Aging
Decomposition of the SSSS - to form the fine precipitates
SSSS * - an unstable condition and easy to form metastable phases to 
lower the energy of the system
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Age-hardening mechanisms
Interaction of (001) glide dislocation with b1’
precipitates. Mg-8Zn-1.5RE. TEM. [0001]Mg
beam direction.Needle-shaped precipitates in a Mg alloy
• dislocation by- passing
Sheared g’ particles in Ni-19Cr-6Al 
aged 540h at 750ºC and deformed 2%
• dislocation cutting or 
shearing of precipitates
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7075-T73: Al-5.6Zn-2.5Mg-1.6Cu, 
Die-forged
Y.S = 430 MPa, T.S = 500MPa, 
Elongation = 13
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Al casting alloys
Cast processes
Sand casting
Permanent mould casting (gravity die casting)
Die casting
Why cast
Low melting temperature, 660º-450ºC (Mg-Al alloys)
Negligible solubility for all gases (except H2)
Good surface finish
Good castability
Good fluidity
Good feeding ability
The major problem
The relatively high shrinkage (3.5-8.5%)
•Al-Si-based cast alloys 3xxx.x
•Maximum solubility of Si in Al: 1.65 wt% at 577ºC
•Eutectic type, eutectic composition: 12.7% Si
Hypoeutectic alloy, Si<12.7%
hypereutectic alloy, Si content >12.7%
• a(Al) - Si phases
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•A390, Al-17Si-4Cu-0.55Mg
•coarse eutectic fi low ductility
•Modification: to refine the eutectic structure
•By adding sodium salts (0.005-0.015%), or phosphorus, or strontium (Sr) (0.03-0.05%)
Si phase
Thin walled cast Al-Si alloy automotive transmission casing.
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Aluminum beverage can in various stages of production including:
drawing, dome forming, trimming, cleaning, decorating, and neck and 
flange forming.
Mg 
atomic number 12
Atomic mass 24.305
Crystal structure hcp, a = 0.32094 nm, c = 0.52107 nm
Melting poing 650ºC
Boiling point 1090 ºC
Density (r) 1.736 g/cm3
Elastic modulus E = 45GPa
Specific modulus E/r = 26
1m3 of sea water contains 1.3 kg magnesium
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• Lowest density (~1.8 g/cm3) of all metallic constructional materials
• High specific strength
• Good castability, suitable for high pressure die-casting
• Good machinability
• High thermal conductivity
• High dimensional stability
• Good electromagnetic shielding property
• High damping characteristics
• 100% recyclability
Applications:
•Transport industry
• Portable electronics
• Telecommunication
The advantages of magnesium alloys
Designation of various Mg alloys
A Al
M Mn
W Y
E rare earth (Ce, La, Nd, etc.)
Q Ag
S Si
K Zr
Z Zn
Y Sb (antimony)
L Li
H Th (thorium)
e.g.
AZ91: Mg-9Al-1Zn
AM60: Mg-6Al-0.3Mn
AE42: Mg-4Al-2RE
AS21: Mg-2Al-1Si
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Cylinder head cover
Hand break leverer-Porsche
Intake manifold-Daimler Chrysler
Intake manifold -Daimler Chrysler
Automotive Applications
Key lock housing
Door-Lupo
Oil pan housing
Oil pan-Honda
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Cock pit component.General Motors
Steering wheel-Ford
Steering wheel-Lupo
Transmission housing
Instrument panel-General Motors
Radiator support 1
Radiator support 2
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Chainsaw-Stihl
Handycam-Sony
laptop
Phone frame-Ericsson
Non Automotive Applications
Prunning shears
Speaker parts
stirrups
Video camera-Sony
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Suitcase frame
Cold chamber process Hot chamber process
High pressure die-casting
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The disadvantages of magnesium alloys:
• Low elastic modulus
• Limited cold workability and toughness (hcp structure)
• Limited creep resistance at elevated temperatures (Tm = 650°C)
• High degree of shrinkage on solidification (high thermal expansion)
• High chemical reactivity (free 3s2 valence electron structure)
• In some applications limited corrosion resistance (electrode potential v = -2.31 V)
Focus:
• To improve high temperatureperformance
• To improve corrosion resistance
Mg-Al-based alloys
• AZ91 (125°C)
• AM alloys - AM60, AM50, AM20
• AS21 (150°C)
• AE42 (150° -175°C)
• Mg-Al-Ca (up to 200°C)
Cast Magnesium Alloys and their applicable temperatures
Y-containing alloys
• EZ alloys (Mg-RE-Zn-Zr) up to 200°C
• QE alloys (Mg-Ag-RE-Zr) (200° -250°C)
• WE alloys (Mg-Y-RE-Zr) (250° -300°C)
• Mg-Sc-Mn-X (300°C)
HZ22 (Mg-Th-Zn-Zr), applicable up to 350°C, but radioactivity problem
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AM50
AZ91
Die-casting of the Mg-Al-based alloys
Die cast AZ91 and AM alloys
5 mm
3 mm
3 mm
AM50, as cast. SEM/SEI. AZ91, as cast. 
5 mm
Cooling rate during solidification: 100-1000ºC/Sec.
Non-equilibrium solidification causes a coring effect in the Mg-Al solid 
solution