characterisation of aa 2198 t851 and aa2139 t3 aluminium ... · aa 2198 t851 and aa2139 t3...

Institute of Materials ResearchMaterials Mechanics and Joining

Solid – State Joining Processes (WMP)GKSS Forschungszentrum Geesthacht

June 2008

Vinícius Toledo Saccon

Characterisation ofAA 2198 T851 and AA2139 T3 Aluminium

Alloy Joined by Friction Stir Welding

Contents

1- Introduction

2- Material

3- Outline

4- Methodology to Produce

the Joints

1- Introduction

2- Material

3- Outline

4- Methodology to Produce

the Joints

5- Process Parameters Study

•Alloy AA2198

•Alloy AA2139

6- Characterization

•Alloy AA2198

• Alloy AA2139

7- Summary and Conclusion


•Alloy AA2198

•Alloy AA2139

6- Characterization

•Alloy AA2198

• Alloy AA2139

7- Summary and Conclusion

1- Introduction

Microstructure and mechanical properties of age hardening alloys are altered by the localised thermal cycle and hot deformation during FSW.

Motivation:• Solid state joining / high potential for structural applications• Weight savings of about 1kg/m compared with riveting.

ObjectiveUnderstand the metallurgical phenomena controlling the microstructure evolution and resulting mechanical properties associated to the friction stir weld process and temper condition.

2- MaterialAA2198 Alloy (Al-Mg-Cu-Li Alloy):

- 1% lithium added to aluminum offers nearly 3% in density advantage (Weight

reduction to compared of common aluminum alloys; increase the elastic modulus

of Al in 6%)

- High mechanical properties at cryogenic temperatures.

- The increase of mechanical properties is due: δ’ (Al3Li), T1 (Al2CuLi) and S‘

(Al2CuMg) phases dispersed. There is also the formation of δ’ - PFZ, δ (AlLi) and

b‘ (Al3Zr).

AA 8090 Al-Li alloy is being used in Airbus A340Aircraft panel welded by Friction stir Welding

2- MaterialAA2139 Alloy (Al-Mg-Cu-Ag alloy):- Good combination of strength, fracture toughness (mainly for AA2139 T8) and fatigue resistance ;- Main precipitates : Ω and θ`(strengthening effect )Addition of small amounts of Ag to Al–Cu–Mg alloy:- Stimulates strengthening (metastable phase, Ω, on 111 planes); - Ideally, Ag additions can promote precipitation along intragranular slip planes that decrease the amount of grain boundary precipitation;- Precipitate morphology remains relatively stable at moderately high temperatures (about 200°C).

Al-Mg-Cu-Ag is a new high strength alloy used in aircraft industries.

Al-Mg-Cu-Ag is a potential combination to develop new alloys to aerospace industries.

3- Outline

4- Methodology to Produce the JointsJoint ConfigurationSimilar-butt joint3.5mm plate thickness

ShoulderPin

Welding Speed

Down force

Rotation Speed

FSW parameters for deeper analysis

Fixed:- Tool Angle (0,5°)- Down force (9,5kN)- Pin and shoulder

Tool DescriptionPin diameter: 5 mm Three FlatsShoulder diameter: 15 mm Scroll

Parameters Analysed:- Welding Speed and Rotation Speed

AA2198 T851 AA2139 T3

250 min/mm – 600RPM


AA2198 T3


Fixed parameter: Rotation Speed: 1200 RPM

334°C

293°C

259°C


>90°

40°

50°

-Peak Temperature [°C]- Bending Test [°]

WP RPM mm/min

1,2 1200 1000

1,8 1800 1000

2,4 2400 1000


AA2198 T851


266°C270°C

275°C

Fixed parameter: Welding speed: 1000mm/min


342°C

285°C

247°C



20°

>90°


600mm/min –250 RPM

WP RPM mm/min

1,2 1200 1000

2,4 600 250

3 3000 1000


AA2139 T3



383°C

328°C

286°C


286°C

341°C 383°C

50°

40°>90°


600mm/min –250 RPM

WP RPM mm/min

1,6 1200 750

2,4 600 250

4,8 1200 250


AA2139 T8



379°C

321°C

336°C258°C


335°C 379°C

>90°>90°

10°


WP RPM mm/min

1,2 1200 1000

2,4 600 250

4,8 1200 250

6- Characterization

AA2198 T851

6- CharacterizationAA 2198 T851 Base Material AnalysisPremilinar analysis

AA2198: Elongated grains were found due the previous material processing beforethe artifical aging (OM). Second phase was found dispersed in Al matrix (SEM).

Transversal view (OM) Transversal view (SEM)

6- CharacterizationAA 2198 T851 Base Material AnalysisChemical qualitative analysis particles (SEM)δ ’ (Al3Li) found

δ ’ (Al3Li)

6- CharacterizationMetallurgical CharacterizationOM Macro and Microstructural Characterization250 mm/min and 600 RPM AA2198 T851

No defect formation

Advancing Side Retreating Side

6- CharacterizationAA 2198 T851 600-250 SEM Analysis

Transition Zone (Tmaz) Stir Zone

Intragranular precipitation disperses in Al matrix, resulting good mechanical properties.

6- CharacterizationAA 2198 T851 Base Material Analysis 1000mm/min and 3000 RPMUndesirable Precipitation - Loss of Mechanical Properties(SEM)

Sir zone

Presence of second phase in boundary grain

6- CharacterizationMechanical CharacterizationMicrohardness 250 mm/min - 600 RPM AA2198 T851

Hv0,2 = 77%Hv0,2 BM

6- CharacterizationMechanical CharacterizationMicroflat Test in Different Temperature250 mm/min - 600 RPM AA2198 T851

R0,2 100°C = 69% R0,2 25°CR0,2 200°C = 65% R0,2 25°C

6- CharacterizationMechanical CharacterizationMicroflat Profile Analysis 250 mm/min - 600 RPM AA2198 T851

Superplasticity! SZ withfine and equiaxed grains

6- CharacterizationMechanical CharacterizationComparative Tensile Test AA2198 T851

6- Characterization

AA2139 T3

6- CharacterizationAA 2139 T3 Base Material AnalysisPremilinar analysis

AA2139: Lower texture provide by previous material processing and probably inferior anisotropy when is compared with AA2198 T851

6- CharacterizationAA 2139 T3 Base Material Analysis

6- CharacterizationMetallurgical CharacterizationOM Macro and Microstructural Characterization250 mm/min and 600 RPM AA2139 T3

No defect formation

Advancing Side Retreating Side

6- Characterization

Coarsening and dissolution of the particles

Hv0,2 = 88% Hv0,2 BM

6- CharacterizationMechanical Characterization

6- CharacterizationMechanical Characterization:Microflat Profile Room Temperature 250-600 AA2139 T3

6- CharacterizationMechanical Characterization:Comparative Tensile Test 250-600 AA2139 T3 and Base Material

R0,2 Weld = 77% R0,2 BM

7- Summary and ConclusionsAA2198

Process Parameters Study:• In general 2198 T3 and T8 joints have shown that the welding speed is inversely proporcional to the stir zone final area and peak temperature;• Area of the stir zone is not significantly affected by rotation speed variation.Characterization Base Material AA2198 T851: • Base material shows high anisotropy degree (yield and tensile strength in longitudinal direction were about 70% larger than the transversal direction);• Microflat tensile testing at high temperature show relatively low properties degradation at 100°C (R0,2=69%R0,2BM) and 200°C (R0,2=65%R0,2BM).Characterization AA2198 T851 600RPM – 250 mm/min: • Intragranular precipitation in the stir zone and TMAZ;• Microhardness in stir zone is about 77% of the base material values;• Tensile tests have shown high strength (about 95% of the BMT), but low ductility if compared with base material (about 10% of the BMT).

7- Summary and ConclusionsAA2139

Process Parameters Study:• Inversely proportional behaviour between welding speed and area of the stir zone was observed for 2139 T3 and T8 joints, however in T8, over 500 mm/min no significant variation of the stir zone areas can be identified;• Low welding speeds usually result in bigger area of the stir zone for all alloys / temper conditions and generally good bending results.Characterization of Base Material AA2139 T3:• Low texture provided by fabrication, where grains are not significantly elongated;• Intra and intergranular precipitation;• Microflat tensile testing at high temperature exhibit a low variation of the tensile properties at 100°C and 200°C (around 95% of the BM), but at 300°C, significant tensile properties degradation was observed.Characterization of AA2139 T3 600RPM – 250mm/min:• Low softening effect was observed in the stir zone (circa 88% of BM hardness), and it could be attributed to the coarsening and dissolution of precipitates;• Tensile and microflat tensile tests have shown a high joint performance, moreover, fracture was observed in the base material.

Thank you for attention!!!

characterisation of aa 2198 t851 and aa2139 t3 aluminium ... · aa 2198 t851 and aa2139 t3...

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