Aluminium Alloy - A201Contents Organised by

Ilyas HussainPG Student

R. Vaira VigneshResearch Scholar

Contents• Introduction• Classification of Al alloys• Composition of A201• Microstructure• Properties (Physical, Mechanical and Thermal properties)• Heat treatment processes• Ageing curve• Precipitation sequence• Advantages• Applications• References

Introduction• Aluminium alloys have been the primary material for the structural parts of aircraft because of

their well known performance, well established design methods, manufacturing and reliable

inspection techniques.

• Although the increased use of composite materials reduced the role of aluminium up to some

extent, high strength aluminium alloys A201 remain important in airframe construction.

• Aluminium is a relatively low cost, light weight metal that can be heat treated (T6 and T7 specific

to A201) and loaded to relatively high level of stresses (Fatigue strength is high in T7 HT).

• It is one of the most easily produced of the high performance materials, which results in lower

manufacturing and maintenance costs.

Classification of Cast Al alloys• The Aluminum Association (AA) has adopted a nomenclature for Cast alloys as follows.

• In the AA system, the second two digits reveal the minimum percentage of Al.

• In Axyy.z, x corresponds to the alloy series; yy corresponds to arbitrary number assigned to the

alloy composition in that series; z takes a value of 0 or 1, denoting casting and ingot respectively.

• A201

• 1xx.x series are minimum 99% Al

• 2xx.x series Cu

• 3xx.x series Si, Cu and / or Mg

• 4xx.x series Si

• 5xx.x series Mg

• 7xx.x series Zn

• 8xx.x series Sn

• 9xx.x other elements

Composition of A201Element Composition (wt. %)

Al 92.6 - 95.1

Cu 4.0 - 5.0

Fe <= 0.10

Mg 0.15 - 0.35

Mn 0.20 - 0.40

Other, each <= 0.030

Other, total <= 0.10

Si <= 0.050

Ag 0.40 - 1.0

Ti 0.15 - 0.35

Microstructure (Before and after HT)• A201 in as-cast condition has a continuous Cu-rich segregation zone identified as CuAl2 (θ) and it

has appeared at the grain boundaries of the α-Al matrix.

• A201 contains 1.9 vol% of the grain boundary segregation.

• T6 HT results in dissolution of the Cu-segregated phase.

• However, a small amount of this phase remained even after the solution treatments.

Microstructure (Before and after HT)

A201 (as Cast condition) A201 (T6 HT)

α-Al

CuAl2

T6

HEAT

TREATED

Mechanical Properties Value Comments

Hardnes Brinell 135 500 kg load, 10 mm ball

Tensile Strength, Ultimate 485 Mpa

Tensile Strength, Yield 435 MPa@Strain 0.200 %

Elongation at Break 7.0 % In 50 mm

Modulus of Elasticity 71.0 GPa In Tension; elastic modulus in compression is typically about 2% higher for aluminum alloys.

Poissons Ratio 0.33

Machinability 90 % 0-100 Scale (100=best)

Shear Modulus 23.0 GPa

Shear Strength 290 MPa Typical for 201.0 - heat treatment unknown

Charpy Impact 10.0 J ±5 J; V-notch

T7

HEAT

TREATED

Mechanical Properties Value Comments

Tensile Strength, Ultimate >= 414 MPa

Tensile Strength, Yield >= 345 MPa@Strain 0.200 %

Elongation at Break >= 3.0 % In 50 mm

Modulus of Elasticity 71.0 GPa In Tension; elastic modulus in compression is typically about 2% higher for Al alloys.

Poissons Ratio 0.33

Fatigue Strength 98.0 MPa@Cycles 5.00e+8 R.R. Moore test, completely reversed bending

130 MPa@Cycles 600000 R.R. Moore test, completely reversed bending

Machinability 90 % 0-100 Scale (100=best)

Shear Modulus 23.0 GPa

Heat treatment (HT) & Temper designation• F - As fabricated• H - Strain hardened (cold worked) with or

without thermal treatment• H1 - Strain hardened without thermal treatment• H2 - Strain hardened and partially annealed• H3 - Strain hardened and stabilized by low

temperature heating• O - Full soft (annealed)• W - Solution heat treated only• T Heat treated to produce stable tempers

• T1 - Cooled from hot working and naturally aged (at room temperature)

• T2 - Cooled from hot working, cold-worked, and naturally aged

• T3 - Solution heat treated and cold worked• T4 - Solution heat treated and naturally aged• T5 - Cooled from hot working and artificially

aged (at elevated temperature)• T6 - Solution heat treated and artificially

aged• T7 - Solution heat treated and stabilized• T8 - Solution heat treated, cold worked, and

artificially aged• T9 - Solution heat treated, artificially aged, and

cold worked• T10 - Cooled from hot working, cold-worked,

and artificially aged

T6 & T7 HT processT6 -

Processing Properties

Temperature Procedure / Period

Solution Temperature 510 - 516 °C

for 2 hr followed by

526 – 532 °C for 14-20 hr and a water quench

Aging Temperature 22.2 °C for 12-24 hr

(Artificially aged) 152 - 157 °C for 20 hr

T7 - Processing Properties

Temperature Procedure / Period

Solution Temperature 510 - 516 °C

for 2 hr followed by

980-990°F for 14-20 hr and a water quench

Aging Temperature 22.2 °C for 12-24 hr

Stabilised

Purpose of HT• Solution heat treating, quenching and ageing are basic heat

treatments for Al alloys. • The proper selection of these heat treatments can achieve

optimum combination of strength and ductility of the material. • Solution treatment is the heating of an alloy to a suitable

temperature, holding it at that temperature long enough to cause one or more constituents to enter into a solid solution and then cooling it rapidly enough to hold these constituents in solution.

• The purpose of solution heat treatment is to put the maximum practical amount of hardening solutes such as Cu, Mg and Si into solid solution of Al – matrix

• The purpose of quenching is to preserve the solid solution formed at the solution heat treating temperature by rapidly cooling to some lower temperature, usually near room temperature

• The purpose of ageing is to increase strength and resistance to corrosion by forming Guinier-Preston (GP) zones and precipitating second-phase particles from solid solution obtained from quenching

Ageing Curve for A201 (Cu – 4.5%)

50 days (approx.)

20 hours(approx.)

Al – Cu Phase diagram

Precipitation Sequence• Immediately after quenching to room temperature the only contribution to strengthening (that is,

resistance to the movement of dislocations) comes from the solid solution: Cu atoms at the Al sites which resist the movement of dislocations.

• However, as the GP zones form, the elastic stresses associated with the coherent GP zones resists the movement of dislocations contributing to hardness.

• As the aging time increases, the coherent θ’’ phases that form, due to the misfit strains that they produce, manage to resist the movement of dislocations and hence lead to further hardening.

• Finally the formation of semi coherent θ’ can also increase the strength• Over ageing

• However, in the case of both θ’ and θ’’ and if the particles are coarser or the volume fractions of these phases are smaller it leads to a decrease in hardness since the dislocations can bow between the precipitates and hence move in the matrix contributing the plastic deformation.

• Higher Temperature• At the higher temperature the peak hardness (the highest hardness that is achieved before over

aging) is lower. This is because the lower driving force at the higher temperature for the formation of the phase leads to a coarsely dispersed phase with lower volume fractions.

Precipitation Sequence• GP zones -> θ’’ -> θ’ -> θ (stable)

Sl GP Zone θ’’ θ’ θ

Size80 Å diameter3 – 6 Å thickness

300 Å diameter20 Å thickness

1000 Å -

Shape

Disk Tetragonala=b=4 Åc=7.8Å

Tetragonala=b=4.04Åc=5.8Å

Tetragonala=b=6.06Åc=4.87Å

Distribution

Homogeneous in Al matrix

Fairly uniform in the Al matrix in coherent interface between precipitate and matrix

Heterogeneous formation in helical dislocation and cell walls

Heterogeneous nucleation in the grain boundaries

Ageing Curve

Advantages

Applications• Aircraft frames• Cylinder Heads• Pistons• Gear housings• Motor cycle engine parts• Structural parts exposed to elevated temperatures (Best combination

of high Strength and Fracture toughness) [1]

References1. ASM International 2004 - Aluminium Alloy Castings: Properties, Processes and Applications by John Gilbert Kaufman

2. The Role of Alloy Composition and T7 Heat Treatment in Enhancing Thermal Conductivity of Aluminum High Pressure Die castings DOI: 10.1007/s11661-012-1443-7

3. Rheological characterization of A201 Aluminum alloy DOI: 10.1016/S1003-6326(09)60351-4

4. Thixo forming A201 aluminium alloy: is there a future in aerospace applications, La Metallurgia Italiana - n. 7-8/2012

5. Aluminium Alloy – Temper Designations, Aalco®

6. OPTIMISATION OF THE SOLUTION HEAT TREATMENT OF RHEOPROCESSED Al-Cu-Mg (Ag) ALLOYS A206 AND A201, Light Metals Technology (LMT2009)

7. Thermo physical properties of A201, A319, and A356 aluminium casting alloys, DOI:10.1068/htjr052

8. The viscosity of aluminium and its alloys—A review of data and models, PROCEEDINGS OF THE 2003 INTERNATIONAL SYMPOSIUM ON LIQUID METALS, JOURNAL OF MATERIALS SCIENCE 39 (2004) 7221 – 7228

9. The Influence of Ageing Time and Temperature on the Structure and Properties of Heat Treated A201.0 Aluminum Alloy, International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277-3878, Volume-3 Issue-3, July 2014

10. Oscillating Cup Viscosity Measurements of Aluminum Alloys: A201, A319 and A3561, International Journal of Thermo physics, Vol. 23, No. 4, July 2002

11. www.matweb.com – Materials properties and data