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Berisi tentang aluminium dan paduannya

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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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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)

  • 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)

  • 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)

  • 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)

  • 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

  • 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

  • Al-Cu Phase Diagram

    ASM; Aluminum and Aluminum Alloys; page 547

  • 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)

  • 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

  • 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

  • PRECIPITATION HARDENING (Cont)

    The effect of aging temperature and time on the yield strength of Al-4% Cu

  • Schematic Aging Curve at A Particular Temperature

    for A Precipitation - Hardenable Alloy

    Smith; Principles of Materials Science & Engineering; page 528

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • Main Aluminum Alloy and Composite Application

    in the Fokker 100

    Wanhill; Damage Tolerance Engineering Property Evaluations; NLR-TP 941774; page 23

  • Jacobs; Engineering Materials Technology; page 288

  • 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

  • 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

  • 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.

  • 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)

  • How to Improve Resistance to

    SCC

    Control of heat treatment:

    Use T73 temper

    Use RRA

  • T73 Heat Treatment

  • RRA Heat Treatment

  • 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