aluminium alloys

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

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.

Specific values of elastic modulus (GPa)

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

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

` 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 %)

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

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

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

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

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

` 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

` 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

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,

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]

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.

` 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

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

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)

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

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

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

` 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)

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

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).

annadanamsreekarHighlight






` 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


` 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



` 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




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

`

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.


` The strongest aluminium alloys (2XXX, 6XXX and 7XXX) are produced by age hardening


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

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)

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





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



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

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




` 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

` 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

` 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)

` 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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aluminium alloys

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conductivity of al

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