Download - Aluminium Alloys
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Properties of pure elements Al Mg Ti Fe Cu Ni
YS (MPa) (annealed) 10 69 171 50 41 60
UTS (MPa) (annealed) 45 185 240 450 215 310
Density (g cm3) 2.7 1.74 4.54 7.86 8.96 8.9
E (GPa) (annealed) 70 45 111 198 116 207
%Elongation (annealed) 50 4 24 54 40
Unit cell fcc hcp hcp, bcc bcc, fcc fcc fcc
MP (C) 660 650 1670 1538 1081 1455
Aluminium and its Alloys
In properly treated condition alloys of light metal posses favourable
` Specific strength = Strength/weight (UTS/density) ` Specific modulus = Stiffness/weight (E/density)
Alloy UTS/density E/density
HSS 170 27
Duralumin 200 26
Mg alloy 190 25
Ti alloy 280 27
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Valence: +3
Density:
Melting Point:
Thermal Conductivity:
Elastic Modulus:
Coefficient of ThermalExpansion:
Cost:
Electrical Resistivity:
Crystal Structure: FCC
0 250 500
0 250 500
0 20 40
0
0.1 1011 102 103 104
50 100
0 1000 2000 3000
0 10 20 252.70 g/cm3
660C
237 W/mK
69 GPa
23.6 m/mC
2.63 cm
1.30 $/kg
Aluminium (Al)
Al
Al
Al
Al
W Fe Al
Al
Cu Co Au
Fe Ti
Fe W
Fe Ag
Fe W
Fe W
Physical properties of Al.
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Specific values of elastic modulus (GPa)
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Aluminium and its alloysfeatures and uses ` Low strength in pure form
Alloying, heat-treatment, and cold-working can improve strength tremendously
Some alloys can be made even stronger than steel
` Light-weight Aerospace alloys, automotive industry
` Corrosion resistant in air and chemical media (pH 4.58.5) Pure Al readily forms a dense, impervious, passive and continuous surface film of
Al2O3 of thickness 2030 on exposure to oxidizing environment
Molar volume of Al2O3 is about 1.3 times that of Al
Surface layer is therefore under compressive stress and readily heals on damage
Can be anodized to improve corrosion resistanceformation of thicker film of
Al2O3
Construction, buildings, and household utensils
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Power transmission lines, cooking utensils, heat sinks
Thermal conductivity is about 60 % that of copper
Equal volume basis: conductivity of Al 60 % that of Cu Equal weight basis: conductivity of Al 200 % that of Cu
` Highly formable fcc: no ductile-to-brittle transition
Complex-sectioned hollow extrusions
` Low melting point Castings: engines and transmissions of automobiles
` Good reflectivity of heat and light Mirrors, heat reflectors
` Impermeable Aluminium foils (thickness < 1 mm) for packaging
` Non-toxic Beverage cans, food packaging, cooking utensils
` Good thermal and electrical conductivity
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` Easy to recycle Energy (only 5 % compared to production of Al) and resource saving
` Non-magnetic Antennas
` Ease of casting ` Variety of surface finishes
Decorative
Aluminium products ` Cast alloys (23 %) ` Wrought products
Standard and special extruded shapes (23 %)
Forgings, impacts (combined extrusion and forging)
Rod, bar, wire, tube (6 %)
Sheet, plate, foil (40 %)
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Limits of use ` Temperature range of -240 C to +200 C for normal alloys ` Up to 350 C for special alloys ` Up to 480 C for short periods for dispersion strengthened alloys ` Low modulus of elasticity, requires stiffening ` Inferior wear, creep, & fatigue properties compared to steel ` High energy requirement for its extraction from ore ` Oxides can make joining rather difficult
Welding is done in inert gas atmosphere
` Corrosion problems Pitting corrosion
Stress-corrosion cracking in precipitation-hardened alloys
Anodic with respect to many elementssacrificial attack of aluminium alloys when
they are in contact with most other metals in corrosive environment
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Alloying elements in aluminium alloys ` Strength can be improved by alloying followed by some hardening process ` Only nine elements have maximum solid solubility in Al (fcc solid solution) greater
than 1 wt. %
These are: Ag, Cu, Ga, Ge, Li, Mg, Mn, Si, Zn
Ag, Ga, Ge: expensive
Li : processing difficulties, only in special alloys
` Heat-treatable alloys contain elements that dissolve substantially at high temperature and precipitates on cooling (Cu, Mg, Zn)
` Casting alloys contain Si which increases fluidity, not sensitive to hot-cracking, and able to fill mould completely
` Si produces a modest increase in strength by forming fibres and particles during solidification
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Non-heat trea tablewrought alloys
Heat treatablewrought alloys
Non-heat trea tablecasting alloys
Heat treatablecasting alloys
Mg,MgMn
MgSi, ZnMg,CuMg, ZnCuMg
Si,SiMg, SiCu
SiMg,CuTiMg
Al(Work-hardening)
` Work hardening alloys produce a fine dispersion of intermetallic phase (Al-Mn) or remain in solid solution (Al-Mg) imparting strength
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Casting alloys Wrought alloys
Work-hardenablealloys
Age-hardenablealloys
Si
Mg
Zn
Cu
Al
Al Si
Al Mg
Al Si Cu
Al Si Mg
Al Mg Si
Al Cu
Al Zn Mg
Al Fe Si
Al Mg
Al Si
Al Mn
Al Mg Mn
Al Zn
Al Mg Si
Al Cu (Si, Mn)
Al Cu Mg
Al Zn Mg
Al Zn Mg Cu
Al Cu (Mg) Li
Fe
Si
Mn
Mg
Zn
Cu
Li
Al
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Alloy type Four-digit designation
Wrought alloys1XXX
Copper 2XXXManganese 3XXXSilicon 4XXXMagnesium 5XXXMagnesium and silicon 6XXXZinc 7XXX
8XXX
1XXXCopper 2XXXSilicon with added copperand}or magnesium 3XXX
Silicon 4XX.XMagnesium 5XXXZinc 7XX.XTin 8XX.XOthers 9XXX
99 wt.% (min) aluminium
99 wt.% (min) aluminium
Others (Li etc.)
Aluminium Alloy Designations
Note: 6XX.X is unused in casting alloys
Cast alloys
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` Aluminium alloys are classified according to their main alloying elements ` Four-digit classification system of Aluminium Association, USA ` Separate designation systems exist for wrought and cast alloys ` Additionally, a temper designation system is used to define different thermal and
mechanical treatments
` Wrought Alloys:
XXX is a code for specific composition First X denotes modifications of the original alloy Last XX denote distinct compositions (except 1XXX: here XXX denotes purity
level) Prefix X is used to denote an experimental alloy
The first digit (18) indicates the alloy group X is a digit 08
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` Cast Alloys: The first digit (19) indicates the alloy group First two XX before the decimal point is a code for composition Last X denotes if the alloy is an ingot (X0) or not (X=0) Often a letter prefix (excluding I, O, Q, X) is used to denote either an impurity
level or the presence of a secondary-alloying element
` Suffix (-Syy) is added to denote thermal/mechanical treatment given (except for
S=H strain-hardened (wrought products only). Strengthening by strain-hardening, with or without supplementary thermal treatments to produce some reduction in
strength. H is always followed by one or more digits S=O annealed. Wrought products which are annealed to obtain the lowest strength
temper, and to cast products which are annealed to improve ductility and
dimensional stability (Dead soft alloys)
S=F as fabricated. No special control over thermal conditions or strain-hardening is employed
ingots)-Temper designations
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S=T thermally treated. Applies to products which are thermally treated, with or without supplementary strain-hardening, to produce stable tempers (age-
hardened). T is always followed by one or more digits
S=W solution heat-treated. An unstable temper applicable only to alloys which spontaneously age at room temperature after solution heat treatment. This
designation is specific only when the period of natural aging is indicated: for
example, W hr
` Examples: 1060-H18: 99.6Al, 0.35Fe, 0.25Si: Architectural, Cookware
1100-H18: 99.0Al, 1.0(Fe+Si),
1199-O: 99.99Al (super purity Al)
2024-T6: 4.4Cu, 1.5Mg, 0.6Mn, 0.5Fe, 0.05Si: Aircraft, Hardware
3003-H18: 1.2Mn, 0.15Cu, 0.7Fe, 0.6Si: Food, Chemical processing
A443.0: 5.25Si,
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1xxx 99%+ Al2xxx Cu3xxx Mn4xxx Si5xxx Mg6xxx Mg+Si7xxx Zn8xxx Li (etc.)
1: Cold-worked only2: Cold-worked & partially annealed3: Cold-worked & fully annealed
1: Partial solution & natural age ing2: Annealed cast products3: Solution & cold-work4: Solution & natural age ing5: Artificial age ing only6: Solution & artificial age ing7: Solution & stabilis ing8: Solution & cold-work & artificial ageing9: Solution & artificial age ing & cold-work
2: hard4: hard6: hard8: Hard9: Extra hard
Fas fabricated
O annealed(wrought only)
Hcold-worked
Theat-treated
xxx is code for specific composition
main alloying addition
Changes denote minor variants
Changes denote distinct alloys
[except 1xxx: xxx denotes purity leve l]
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Aluminum-alloy temper designation
Letter Description
F As manufactured or fabricated
O Annealed
H Strain hardened (wrought products only) : H1x: Strain hardened only H2x: Strain hardened only and partially annealed to achieved required temper H3x: Strain hardened only and stabilized by low-temperature heat treatment to achieve required
temper H12, H22, H32: Quarter hard, equivalent to about 2025% cold reduction H14, H24, H34: Half hard, equivalent to about 35% cold reduction H16, H26, H36: Three quarter hard, equivalent to about 5055% cold reduction H18, H28, H38: Fully hard, equivalent to about 75% cold reduction
W Solution heat treated
T Thermally treated to produce stable tempers other than F, H, and O. Usually solution heat treated, quenched, and precipitation hardened. T1: Cooled from elevated-temperature shaping process and aged naturally to a substantially
stable condition T2: Cooled from elevated-temperature shaping process, cold worked, and aged naturally to
a substantially stable condition T3: Solution heat treated, cold worked, and aged naturally to a substantially stable condition T4: Solution heat treated and aged naturally to a substantially stable condition T5: Cooled from elevated-temperature shaping process, and then aged artificially T6: Solution heat treated, then aged artificially T7: Solution heat treated, then stabilized (overaged) T8: Solution heat treated, cold worked, then aged artificially T9: Solution heat treated, aged artificially, then cold worked T10: Cooled from an elevated- temperature shaping process, artificially aged, then cold worked
Note: A large number of numeric additions have been introduced to indicate specific variations.
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` Non-heat-treatable alloys can be cold-worked to increase strength ` Most can not be precipitation strengthened ` The 1XXX, 3XXX, 5XXX, and most of the 4XXX wrought alloys are not age-
hardenable
` The heat-treatable aluminum alloys of the 2XXX, 6XXX, and 7XXX groups are age-hardenable
` Thus their use is not for moderate (~200C) or high temperature applications.
Role of important alloying elements in aluminium alloys
` Copper (2XXX) Causes age-hardening in several alloys (wrought and cast) Also imparts solid solution strengthening Up to 4% in wrought alloys and up to 8% in castings; generally along with other
alloying elements
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Generally decreases corrosion resistance Copper containing alloys are prone to intergranular corrosion; mainly due its
presence in micro-constituents (Cr is added to counter it)
In small amounts (0.050.2 %) beneficial for corrosion resistance
Decreases shrinkage and hot shortness in cast alloys Often used in combination with Mg in heat-treatable alloys
` Magnesium (5XXX, 6XXX) 110% Decreases density Used mainly in non-heat treatable grades (3XXX, 5XXX) and heat-treatable
grades containing Cu, Si, and Zn (2XXX, 4XXX, 6XXX, 7XXX)
In several 2XXX grades (e.g. 2024) to accelerate age-hardening, thus response
to heat-treatment is much more pronounced
Causes strength to increase without unduly decreasing the ductility Improves machineability, weldability, ductility Improved corrosion resistance when present in small amounts (esp. in alkaline and
marine environment)
In 3XXX series--to improve work hardening characterstics
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Improves casting qualities: increases fluidity (of Al-Si eutectic), low shrinkage, decreases hot shortness, enhances corrosion resistance, lowers thermal expansion
coefficient, increases thermal conductivity, lowers melting point
In Mg alloys it is added as a secondary alloying element for forming Mg2Si precipitates beneficial for age hardening (6XXX)
Also present in some non-heat treatable 3XXX alloys along with Mn, mainly for strength
` Manganese (3XXX) Added up to ~1.5% in non-heat treatable wrought alloys
Solid solution strengthening + strengthening due to presence of precipitates
Further increase in strength when Mg is present (e.g. 3004: 1.2Mn, 1Mg, 0.2Cu)
Added in small amounts to increase the strength Example: Added to Al-Cu-Mg alloys to form the fine dispersion of Al20Cu2Mn3
Decreases ductility (formation of coarse intermetallic phases such as Al6Mn)
` Silicon (4XXX, 6XXX) Present as an impurity in many grades (along with Fe) or added intentionally 114% (as a primary or secondary alloying element)
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Improves intergranular and stress corrosion resistanceAl6Mn has approximately same standard electrode potential as Al and dissolves Fe and Si
In CP aluminium Mn can be a minor impurity, usually between 5 and 50 ppmdecreases conductivity
` Zinc (7XXX) Up to 10 %, main alloying element in some of the strongest heat treatable Al-
alloys (7075, 7050, and 7049)
Added along with other elements to improve mechanical properties through formation of hard intermediate phases such as MgZn2
Used along with Mg and Cu
` Lithium (8XXX) Most important recent addition Used in high strength and low density alloys, and also in some cryogenic alloys
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Low ductility Textured and therefore anisotropic Added along with Cu and Mg
` Chromium Up to 0.35%, mainly in 5XXX, 6XXX, and 7XXX Added to control recrystallization and grain growth
Cr has slow diffusion rate in Al
Can form finely dispersed intermetallic phases in wrought products that
prevents nucleation and grain growth
In 5XXX series, added to prevent grain growth
In 6XXX and 7XXX, added to delay recrystallization during heat treatment
and hot working
Good finish after anodizing (golden colour)being replaced by Ce Improves corrosion resistance of Cu and Mg containing alloys
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In CP aluminium Cr can be a minor impurity, usually between 5 and 50 ppmdecreases conductivity
` Nickel Improves strength and hardness at elevated temperatures (2XXX, 4XXX)
Decreases corrosion resistance
` Iron Dominant impurity in virtually all commercial alloys, high solubility in molten Al
but solubility is very low in solid state
Present as coarse intermetallic precipitatesreduces fracture toughness and fatigue-crack-initiation and fatigue-crack-propagation resistance
Usually kept below 1%
Reduces coefficient of thermal expansion
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` Lead, Tin, Bismuth, Cadmium Used in free-machining grades of Al alloys (improved machinability by forming soft
low-melting phases)
Example: Al-5.5Cu-0.4Bi-0.4Pb (2011)
` Na, Sr: modifiers (alters eutectic microstructureshape, size, and distribution of precipitates) in cast alloys
Sodium causes hot cracking in 5XXX
` B, Nb, Sc, Ti: added for grain refinement Example: 7020 (Al-4.5Zn-1.2Mg) grain refined with Sc
` Zr: forms fine intermetallic phase that inhibits recovery and recrystallization and thus grain structure (used extensively in 7XXX alloys containing Mg)
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Strain Hardening `
Strain hardening curves for alloys
1100 (99Al), 3003(Al-1.2Mn),
5050(Al-1.4Mg) and 5052 (Al-2.5Mg)
` Note initial rapid rise of YS and decrease in ductility
Aluminium and its Alloys: Strengthening Mechanisms
Particularly useful for non-heat treatble grades
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Alloying increases rate of dislocation production, reduces recovery rate, increases
effectiveness of dislocations as barriers for metal flow
Cu is very effective, but usually kept < 0.3 % in non-heat treatable wrought
alloys to avoid formation of insoluble intermetallic phases
Mg is less effective than Cu, but has high solid solubility in (Al)
Zn has only negligible effect on strain hardening
` Strain hardening behaviour can be influenced by alloying:
Al-4.5% Mg
Al-2.0% Mg
Al-0.5% Mg
High-purity A
l
0.1 0.2 0.5 1 2 5
500
300
200
100
50
Y
i
e
l
d
S
t
r
e
n
g
t
h
(
M
P
a
)
True Strain
Strain-hardening response from cold-rolling high-purity Al and Al containing varying amountsof Mg (wt%). True strain = 1.15 ln (initial thickness/nal thickness).
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` Strain hardening characteristic changes with temperature
` Strain hardening ability decreases as the temperature increases due to dynamic recovery and recrystallization
m) (T should be < 0.3 T
Example: Cryorolling of 1100-O
As much as 40% improvement inwork hardening, but ductility issignificantly reduced
cross-slip difficult at low T
recovery and recrystallization can occur
effectiveness of strain hardening disappears at temperatures where dynamic
low temperatures - strain hardening rate higher than at room temperarture
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` For significant s-s-s misfit and RT solubility must be highsolid solubility of Mg and Zn in (Al) is about 2 wt.%, where as most other elements solubility is less than
` The atomic radius comparison between Al and common alloying elements can be
` Mg additions (r = 0.018 nm) have a greater strengthening effect than additions of Si (r = 0.024 nm), Cu (r = 0.016 nm), Ti (r = 0.004 nm) and Zn (r = 0.005
nm).
5
4
3
2
1
00 1 2 3 4 5 6
Mg
Cu
SiZn
wt. %
used as a guide to potency of s-s-s
Solid Solution Strengthening (s-s-s) in Aluminium Alloys
` Particularly useful for non-heat treatable grades
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` Grain refinement improves not only strength, but also the toughness of many alloys.
` Ductility is not significantly reduced by grain refinement ` In Al alloys grain refinement is achieved by
fast cooling (lots of nucleation due to high T)
adding grain refining elements (e.g. B, Ti, etc.)
cold working (e.g. cryorolling), recovery, recrystallization electromagnetic stirring or ultrasonic vibrations during solidification
Grain Boundary Strengthening
Max. age hardening: critical dispersion of GP zones or intermediate precipitates or both
Peak strength is associated with critical particle size and distributionsufficient
precipitation, but not too large in size
`Age Hardening
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Higher the ageing temperature faster the ageing processdue to faster diffusion Peak strength is reached fast, thereafter strength decreases due to overageing
Caution: High ageing temperature degree of super saturation reduced, amount of precipitation reduced, and strength lowered
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120
100
80
60
0.01 0.1 1 10 100 103
Aging Time (days)
H
a
r
d
n
e
s
s
(
V
H
N
)
130C
190C
GP2
GP2
GP1
Hardness versus aging time in a binary Al4 wt% Cu alloy solutionized, quenched, and agedMaximum hardness occurs on both curves when a mixed GP2+
microstructure is present.
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` The strongest aluminium alloys (2XXX, 6XXX and 7XXX) are produced by age hardening
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Related phenomena during age hardening ` Overaging at grain boundaries
Nucleation of precipitates can happen either homogenously or by heterogeneously
Preferred sites for heterogeneous nucleation are grain boundaries and dislocations
At these sites overaging occurs (by Ostwald ripening) much before the matrix
has fully aged
` Recrystallization of the matrix during aging treatment ` Widmansttten structure formation
A structure characterised by a geometric pattern resulting from the formation of
a new phase (plate or needle-shaped) on certain crystallographic planes in the
parent phase
The orientation of the lattice in the new phase is related to the orientation of the
lattice in the parent phase
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grai
n bo
unda
ry
PFZ in an Al-Ge alloy
Regions adjacent to the grain boundaries which are denuded of precipitates or zones
All alloys involving refined dispersions of a second phase tend to produce PFZs
` Formation of precipitation-free zones (PFZ)
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1. depletion of excess vacancy concentration
in these regions next to the boundaries
precipitation)
Vacancy concentrations are influenced by
the presence of a grain boundary because
the boundary acts as a sink for vacancies
Far from the boundary, the vacancy
concentration will be the equilibrium
value for the solutionizing temperature
and near the boundary, the concentration
will be that for the aging temperature
When the vacancy concentration drops in
the vicinity of the boundary, it reduces
below the critical concentration for GPZ
formation
Two contributing factors for formation of PFZs
Critical vacancyconcentration for GPzone formation
Solute concentration
Actual vacancy concentration
PFZ
(recall that vacancies are essential for
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The solute concentration usually
decreases by an amount which is
considerably less than that corresponding
to the vacancy concentration
The rate of quenching also affects the
PFZ width because during a slow quench,
there is more time for the vacancies to
diffuse to boundaries and be annihilated
2. depletion of solute near to the boundary because of diffusion of solute to the
boundary where large particles are formed
Usually the solute profile at a boundary is not as pronounced as the vacancy
concentration
This is not the case when particles precipitate at boundaries because of
heterogeneous nucleation, depleting solute from the surrounding matrix, and grow
by Ostwald ripening because of fast diffusion down the boundaries
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Critical concentrations forG P zone formation:
solutevacancies
Profile of soluteconcentration
V acancyconcentration
Precipitate particle
PFZ
PFZ in Al-4Zn-3Mg aged at 150 C for 24 h PFZ in Al-Zn-Mg-Cu alloy
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Wide PFZs are undesirable because they adversely affect the mechanical an
corrosion properties of the alloy
PFZ may be reduced by: alloying with trace elements
lower ageing temperature
faster quench rates
Reduced pfz size when 0.3%Ag is added to Al-4Zn-3Mg alloy
(aged at 150C for 24 hrs) - compare with previous micrograph
Here Ag raises the GP zone solvus temperature
The pfz size is drastically reduced by the raising of the GP solvus
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` 2024: Al-4.4Cu-1.5Mg-0.6Mn Superseded 2017 (Duralumin: Al-4.4Cu-0.8Si-0.5Mg-0.8Mn) Uses: High strength fabricated or machined items in aircraft industries, general
engineering, machinery, military equipment, truck wheels. Screw machine products.Structural applications. Rivets (e.g. in aircraft structural).
Characteristic Properties: Heat treatable alloy. Very good machiningcharacteristics. High strength alloy. High fatigue strength. Poor weldabilityelectron beam welding preferred. Corrosion resistance only with cladding or otherprotection. Natural ageing.
After solutionizing rivet is kept under refrigeration (to prevent aging and loss ofductility)
Riveting (cold work) causes strain-induced aging
The strength-aging time plot of these alloys must be known very accurately inorder to service the part (replacement of rivet) before loss of strength occursthrough over-aging
The flight schedule of the airplane is part of the maintenance program as the agingrate is reduced during flight in low temperature air
Available in O(YS 75 MPa), T3(YS 340 MPa), T4(YS 330 MPa), and T8(YS 450MPa) tempers
T3 and T4 tempers are usually stable after natural ageing of ~1 week
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` 3004: Al-1.3Mn-1.1Mg Extra Mg in 3004 makes it stronger (YS 75 MPa for 3004-O, 295 MPa for 3004-
Forming characteristics most suitable for beverage can body Aluminium beverage cans are fabricated from two parts:
the can body, generally made from 3004 (or 3104) sheet, and
3104 is sold in the H19 hard rolled temper After manufacture, the can body and can end are transported to a filling plant
the can end, typically made using 5182 due to its higher strength
using a folded seam and a small amount of a sealing compound where the beverage is put into the can and the two components are attached
H19) than 3003
` 4032: Al-12.2Si-1Mg-0.9Cu-0.9Ni Heat treatable
Excellent elevated temperature properties due to Ni
4032-T6: YS 317 MPa, UTS 380 MPa (at 25C)
UTS 270 MPa (at 270C)
Corrosion resistance is not good (due to presence of Cu and Ni)
Products: Forged pistons in IC engines
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` 5182: Al-4.5Mg-0.3Mn (Packaging: container ends, can stock. Motor vehicles: automotive body panels and reinforcement members, brackets and parts.)
5182 alloy was designed for manufacturing of beverage can easy-opening ends
which require maximum strength to ensure minimum thickness and lowest cost. It
is also used for formed parts in automotive bodies but stretcher-strain marks which
can occur on forming mean that it is restricted to inner panels, brackets and
supports which are not visible in the final structure
5182-O (YS 135 MPa), 5182-H18 (YS 310 MPa)
` 6082: Al-0.9Mg-1Si-0.7Mn (Heavy duty structures in rail coaches, truck frames, ship building, offshore, bridges, military bridges, bicycles, boilermaking. Machinery:
platforms, flanges, hydraulic systems, mining equipment, pylons and towers,
motorboats. Nuclear technology. Masts and beams for ship building. Tubes forscaffolding, framework for tents and halls, piping, tubing Screw machine products.
Rivets.)
Not suitable for complex shapes
6082-O (YS 60 MPa), 6082-T6 (YS 310 MPa)
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` 7075: Al-5.6Zn-2.5Mg-1.6Cu-0.23Cr-0.3Mn (Aircraft and military highly stressed structural components. Rolling stock for machine parts and tools (for rubber and
plastics). Ski poles, tennis rackets, screws and bolts, nuts. Rivets. Nuclear
applications.)
Heat treatable very high strength alloy with a strength slightly lower than 7010.
Very high fatigue strength. Joining preferably by rivets, adhesives or screws.
Corrosion protection is recommended also in outdoor atmosphere.
Care to be taken when selecting temper (and other thermal treatment) for balance
of properties. May be clad with 7072 for better protection against stress corrosion
cracking.
7075-O (YS 105 MPa), 7075-T651 (YS 503MPa), 7075-T73 (YS 420 MPa)
` 7475: Al-5.7Zn-2.2Mg-1.6Cu-0.22Cr-0.06Mn Lower impurity specification than 7075, better resistance to stress corrosion
cracking
7475-T651 (YS 510MPa)
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