paduan aluminum
DESCRIPTION
Berisi tentang aluminium dan paduannyaTRANSCRIPT
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Paduan Aluminum
Pendahuluan
Sifat-sifat Paduan Aluminum
Klasifikasi dan Penamaan Paduan Aluminum
Perlakuan Panas Paduan Aluminum
Pemakaian pada Struktur Pesawat
Masalah Stress Corrosion Cracking pada paduan 7XXX
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1.Pendahuluan
Alasan paduan Aluminum masih banyak dipakai pada pesawat penumpang
komersial, namun semakin berkurang
pada pesawat tempur
Sifat-sifat paduan Aluminum yang menyebabkan dipakai pada struktur
pesawat menggantikan kayu
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2. Sifat-sifat Paduan Aluminum
1. Low specific gravity (lightweight)
Mg Al Ti Fe
sg (gr/cm3) 1.8 2.7 4.5 7.8
2. Can reach sufficiently high strength
Some alloys have ultimate strength of 700 MPa
3. Good corrosion resistance
4. Good electrical conductor
5. Good heat conductor
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Designation System
Wrought Aluminum and Aluminum Alloy
Aluminum, 99.00% 1xxx
Aluminum alloys grouped
by major alloying elements :
Copper 2xxx
Manganese 3xxx
Silicon 4xxx
Magnesium 5xxx
Magnesium and Silicon 6xxx
Zinc 7xxx
Other elements 8xxx
Cast Aluminum and Aluminum Alloy
Aluminum, 99.00% 1xx.x
Aluminum alloys grouped by major
alloying element(s) :
Copper 2xx.x
Silicon + Copper & or Magnesium 3xxx
Silicon 4xxx
Magnesium 5xxx
Zinc 7xxx
Other elements 8xxx
3. Klasifikasi dan Penamaan
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3. Klasifikasi dan Penamaan
Alloy Group Major alloying
element u (MPa) Designation
Commercially pure
aluminum
- 90 - 170 1xxx
Non-heat treatable
with age hardening
Mn
Mg
100 - 200
200 - 300
3xxx
5xxx
Heat treatable with
age hardening
Cu
Mg + Si
Zn
400 500 250 350 520 - 650
2xxx
6xxx
7xxx
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Wrought Aluminum Alloy
First digit major alloying element(s)
Second digit indicates alloy modification :
- zero means original alloy
- integer one to nine, assigned consequentially indicate
modification of the original alloy
Third and forth digit : identify different alloy
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Example of Wrought Aluminum Alloy Designation
2 0 1 4
alloy identification
original alloy
Cu major alloying element
Application
Heavy duty forgings, and extrusions for aircraft fittings, wheels
Truck frame and tankage
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2 0 2 4
alloy identification
original alloy modified alloy
Cu major alloying element
2 1 2 4
2 2 2 4
2 3 2 4
Application
2024 used in aircraft structure requiring high fatigue strength
differ with the original
alloy in Si and Fe content
(higher purity) higher
fracture toughness
Example of Wrought Aluminum Alloy Designation (cont)
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2 2 1 9
alloy identification
modified alloy
Cu major alloying element
Application
For cryogenic and elevated temperature (supersonic aircraft skin)
Weldable welded space booster oxidizer and fuel tank
Example of Wrought Aluminum Alloy Designation (cont)
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7 0 50
alloy identification
original alloy
Zn major alloying element
Application
Plate, extrusions, hard and die forgings in aircraft structural parts
Application requiring high strength, high resistance to exfoliation
corrosion, stress corrosion cracking, high fracture toughness and
high resistance
Example of Wrought Aluminum Alloy Designation (cont)
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7 0 75
alloy identification
original alloy modified alloy
Zn major alloying element
7 1 7 5
7 4 7 5
Application
7075 used in aircraft structural parts requiring very high strength
7175 forgings requiring high strength
7475 sheet and plate (fuselage or wing) for high strength and high
fracture toughness
differ with the original
alloy in Si and Fe content
(higher purity)
Example of Wrought Aluminum Alloy Designation (cont)
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Typical Composition of Some Aluminum Alloys
Al - Zn 7050 2.3 2.3 0.12 0.15 6.2 0.1 0.04
1.6 2.5 5.6 0.3 0.23
1.6 2.5 5.6 0.1 0.23
1.5 2.3 5.7 0.06 0.22
Alloy System Designation Cu Mg Si Fe Zn Mn Cr
Al - Cu 2014 4.4 0.5 0.8 0.7 0.25 0.8 0.1
4.4 1.5 0.25 0.6 0.1
4.4 1.5 0.35 0.6 0.1
4.1 1.5 0.25 0.6 0.1
2024
2124
2224
0.5 0.5
0.2 0.3
0.12 0.15
7075
7175
7475
0.4 0.5
0.15 0.2
0.1 0.12
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PRECIPITATION HARDENING
In dispersion strengthened alloy more than one phase must be present
Matrix is a phase with larger amount, the other phase (smaller amount is
precipitate)
Consideration for effective precipitation hardening
4. Perlakuan Panas
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Al-Cu Phase Diagram
ASM; Aluminum and Aluminum Alloys; page 547
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Without special heating cycle precipitation will not result in
appreciable strengthening
Al - Cu phase diagram and the microstructures that may develop during cooling
PRECIPITATION HARDENING (Cont)
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Precipitation Hardening produces uniform dispersion of a fine,
hard coherent precipitate in a softer, more ductile matrix.
Three steps in precipitation hardening :
1. Solution treatment : heating above
solvus dissolve in . For Al-
Cu it is carried out between 500oC -
548oC
2. Quench : The alloy which only
consist of phase is quenched,
is not formed. Existing phase is
super saturated solid solution
(sss)
3. Age : supersaturated is heated
below solvus atoms diffuse at
short distance at numerous
nucleation sited fine
intermediate phases is formed
and dispersed in the matrix
Precipitation Hardening of Al-4% Cu
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Precipitation Hardening of Al-4% Cu
Microstructures :
1. Supersaturated solid solution
2. GP1 zone Cu segregate in
disks with thickness 0.4 - 0.6
nm, diameter a few atom
3. GP2 larger than GP1, thickness
1 - 4 nm, diameter 10 - 100 nm
4. equilibrium phase with
composition Cu Al2
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PRECIPITATION HARDENING (Cont)
The effect of aging temperature and time on the yield strength of Al-4% Cu
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Schematic Aging Curve at A Particular Temperature
for A Precipitation - Hardenable Alloy
Smith; Principles of Materials Science & Engineering; page 528
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PRECIPITATION HARDENING (Cont)
Although is formed and distributed in the matrix , it does not
disrupt the surrounding structure because it is not coherent with
the matrix
Non-coherent precipitate Coherent precipitate
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System for Heat-Treatable Alloys
T3 and T4 : solution heat treatment, quench, naturally
aged
T6, T7, T8, and T9 : solution treatment, quench, artificially aged
T1, T2, T5, T10 : cooled from elevated temperature shaping
process
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T3 and T4 (Natural Aging)
T3 : Solution heat-treated, cold worked, and naturally aged
to a substantially stable condition: Applies to products that are cold worked to improve strength after solution heat treatment, or
in which the effect of cold work in flattening or straightening is
recognized in mechanical property limits.
T4 : Solution heat treated and naturally aged to a
substantially stable condition : Applies to products that are not cold worked after solution heat treatment, or in which the effect
of cold work in flattening or straightening may not recognized in
mechanical property limits
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T6, T7, T8, and T9 (Artificial Aging)
T6 : Solution heat treated and then artificially aged: Applies to products that are not cold worked after solution heat treatment, or
in which the effect of cold work in flattening or straightening may
not be recognized in mechanical property limits
T7 : Solution heat treated and stabilized: Applies to products that are stabilized after solution heat treatment to carry them beyond
the point of maximum strength to provide control of some special
characteristic
T8 : Solution heat treated, cold worked and then artificially
aged, : Applies to products that are cold worked to improve strength, or in which the effect of cold work in flattening or
straightening is recognized in mechanical property limits
T9 : Solution heat treated, artificially aged, and then cold
worked: Applies to products that are cold worked to improve strength
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T1, T2, T5, T10 (Cooled from Elevated-Temperature
Shaping Process)
T1 : Cooled from an elevated-temperature shaping process
and naturally aged to a substantially stable condition:Applies to products that are not cold worked after cooling from an
elevated-temperature shaping process, or in which the effect of cold
work in flattening or straightening may not be recognized in
mechanical property limits
T2 : Cooled from an elevated-temperature shaping process,
cold worked, and naturally aged to a substantially
stable condition: Applies to products that are cold worked to improve strength after cooling from an elevated-temperature shaping
process, or in which the effect of wold work in flattening or
straightening is recognized in mechanical property limits
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T5 : Cooled from an elevated-temperature shaping process
and then artificially aged: Applies to products that are not cold worked after cooling from an elevated-temperature shaping
process, or in which the effect of cold work in flattening or
straightening may not be recognized in mechanical property limits
T10 : Cooled from an elevated-temperature shaping process,
cold worked, and then artificially aged: Applies to products that are cold worked to improve strength, or in which the
effect of cold work in flattening or straightening is recognized in
mechanical property limits
T1, T2, T5, T10 (Cooled from Elevated-Temperature
Shaping Process) - cont
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Temper with natural aging : T1, T2, T3, T4
Temper with artificial aging : T5, T6, T7, T8, T9, T10
Temper with Natural & Artificial Aging
Temper with Cold Work & Without Cold Work
Temper with cold work: T2, T3, T8, T9, T10
Temper without cold work : T1, T4, T5, T6, T7
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5. Pemakaian Pada Struktur Pesawat
Aluminum 2XXX 2024-T3 untuk bagian yang memerlukan ketahanan lelah tinggi
Aluminum 7XXX 7075-T6 untuk bagian yang memerlukan kekuatan tinggi
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Main Aluminum Alloy and Composite Application
in the Fokker 100
Wanhill; Damage Tolerance Engineering Property Evaluations; NLR-TP 941774; page 23
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Jacobs; Engineering Materials Technology; page 288
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Stress Corrosion Cracking
A form of intergranular corrosion resulting from the combined action of applied tensile stress and a corrosive
environment; both factors are necessary
This type of corrosion is associated with cracking which propagate in the direction perpendicular to the stress
Residual stress is introduced in 7XXX alloy during quenching in cold water quench
Cracks may turn at relatively low stress levels, significantly below the tensile strength
Masalah SCC pada paduan 7XXX
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Heat-treatable by Age Hardening Alloy
Series 7xxx (Cont)
A modification of 7075 is the 7175 and 7475 with lower
content of Fe & Si, has high KIC above
However, quenching stresses in T6 contributed to SCC, to
overcome this problem the alloy is given T73 or T76
mMPa50
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Non Heat-treatable by Age Hardening Alloy
Polmear, Light Alloys Metallurgy of the Light Metals, Second Edition, fig. 3.26, pp. 100.
Stress-corrosion cracks in a cold-water
quenched Al-Zn-Mg-Cu alloy forging.
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Non Heat-treatable by Age Hardening Alloy
Polmear, Light Alloys Metallurgy of the Light Metals, Second Edition, fig. 3.28, pp. 102.
Die-forged 7075-T73 integral centre engine support and
vertical stabilizer spar for McDonnell-Douglas DC-10
aircraft. Four similar forgings are used in each aircraft
(from Hunsicker, H.Y., Rosenhain Centenary Conference
on the Contribution of Physical Metallurgy to Engineering
Practice, The Royal Society, London, 1976)
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How to Improve Resistance to
SCC
Control of heat treatment:
Use T73 temper
Use RRA
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T73 Heat Treatment
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RRA Heat Treatment
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RRA Heat Treatment
Apply T6 treatment: solution treatment at 465C,
cold water quench, age at 120C
Heat for a short time (e.g 5 minutes) at 200-280C, water
quench
Re-age 24 h at 120C