Mechanical and metallurgical properties and forces of immersed friction stir welding of aa6061 t6
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Mechanical and Metallurgical Properties and Forces of Immersed Friction Stir Welding of AA6061-T6. Thomas Bloodworth Vanderbilt University. Overview. Introduction Theory and Objective VWAL Test Bed Experimental Setup Materials Testing Results and Conclusions Future Work. Introduction.

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Mechanical and metallurgical properties and forces of immersed friction stir welding of aa6061 t6 l.jpg
Mechanical and Metallurgical Properties and Forces of Immersed Friction Stir Welding of AA6061-T6

Thomas Bloodworth

Vanderbilt University

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Overview l.jpg
Overview Immersed Friction Stir Welding of AA6061-T6

  • Introduction

  • Theory and Objective

  • VWAL Test Bed

  • Experimental Setup

  • Materials Testing

  • Results and Conclusions

  • Future Work

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Introduction l.jpg
Introduction Immersed Friction Stir Welding of AA6061-T6

  • Friction Stir Welding (FSW)

  • Frictional heat with sufficient axial (z) force plasticizes weld-piece (Thomas et al)

  • Advantageous to conventional welding techniques

  • Welds maintain up to 95% of UTS compared to parent material

Schematic of the FSW Process (Record JH, 2005)

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Introduction4 l.jpg
Introduction Immersed Friction Stir Welding of AA6061-T6

  • Light weight materials used in production (e.g. Aluminum)

  • FSW is used primarily to weld Aluminum Alloys (AA)

  • Process currently becoming more prevalent:

    • Aerospace (e.g. Boeing, Airbus)

    • Automotive (e.g. Audi)

    • Marine (SFSW / IFSW)

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Objective l.jpg
Objective Immersed Friction Stir Welding of AA6061-T6

  • Submerged / Immersed FSW (SFSW / IFSW)

  • Joining of the weld piece completely submerged in a fluid (i.e. water)

  • Greater heat dissipation reduces grain size in the weld nugget (Hofmann and Vecchio)

    • Increases material hardness

    • Theoretically increases tensile strength

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Objective6 l.jpg
Objective Immersed Friction Stir Welding of AA6061-T6

  • Hofmann and Vecchio show decrease in grain size by an order of magnitude

  • Increase in weld quality in SFSW may lead to prevalent use in underwater repair and/or construction (Arbegast et al)

    • Friction Stir Spot Welds (FSSW)

    • Repair of faulty MIG welds (TWI)

  • Process must be quantitatively verified and understood before reliable uses may be attained

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Slide7 l.jpg

VWAL Test Bed Immersed Friction Stir Welding of AA6061-T6

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


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VWAL Capabilities Immersed Friction Stir Welding of AA6061-T6

  • VUWAL Test Bed: Milwaukee #2K Universal Milling Machine utilizing a Kearney and Treker Heavy Duty Vertical Head Attachment modified to accommodate high spindle speeds.

  • 4 – axis position controlled automation

  • Experimental force and torque data recorded using a Kistler 4 – axis dynamometer (RCD) Type 9124 B

  • Rotational Speeds: 0 – 4000 rpm

  • Travel Speeds: 0 – 30 ipm

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Vwal test bed l.jpg
VWAL Test Bed Immersed Friction Stir Welding of AA6061-T6

  • Anvil modified for a submerged welding environment

  • Water initially at room temperature

  • Equivalent welds run in air and water for mechanical comparison (i.e. Tensile testing, Cross Sectioning)

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Experimental setup l.jpg
Experimental Setup Immersed Friction Stir Welding of AA6061-T6

  • Optimal dry welds run 2000 rpm, 16 ipm

  • Submerged welds speeds: 2000 – 3000 rpm, travel speeds 10 – 20 ipm

  • Weld samples

    • AA 6061-T6: 3 x 8 x ¼” (butt weld configuration)

  • Tool

    • 01PH Steel (Rockwell C38)

    • 5/8” non – profiled shoulder

    • ¼” – 20 tpi LH tool pin (probe) of length .235”

  • Clockwise rotation

  • Single pass welding

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Experimental procedure l.jpg
Experimental Procedure Immersed Friction Stir Welding of AA6061-T6

  • Shoulder plunge and lead angle: .004” , 20

  • Fine adjustments in plunge depth have been noted to create significant changes in force data as well as excess flash buildup

  • Therefore, significant care and effort was put forth to ensure constant plunge depth of .004”

    • Vertical encoder accurate to 10 microns

  • Tool creeps into material from the side and run at constant velocity off the weld sample

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Materials testing l.jpg
Materials Testing Immersed Friction Stir Welding of AA6061-T6

  • Tensile testing done using standards set using the AWS handbook

  • Samples milled for tensile testing

  • Tensile specimens were milled for each weld run

    • Nominal ½ “ wide x ¼ “ thick specimens were used for the testing

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


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Materials Testing Immersed Friction Stir Welding of AA6061-T6

  • Tensile specimens tested using an Instron Universal Tester

  • Recorded values included UTS and UYS in lbf

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Results l.jpg
Results Immersed Friction Stir Welding of AA6061-T6

  • Stress – Strain curves were generated from the data gathered from the tensile test

  • Weld pitch “rule” is not followed in IFSW (Revolutions / Inch)

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Results15 l.jpg
Results Immersed Friction Stir Welding of AA6061-T6

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Cross section l.jpg
Cross Section Immersed Friction Stir Welding of AA6061-T6

  • Dry Weld Section (left)

  • IFSW (right)

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Cross section17 l.jpg
Cross Section Immersed Friction Stir Welding of AA6061-T6

  • Dry FSW 10x (left)

  • SFSW 50x (right)

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Results18 l.jpg
Results Immersed Friction Stir Welding of AA6061-T6

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Results19 l.jpg
Results Immersed Friction Stir Welding of AA6061-T6

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Results20 l.jpg
Results Immersed Friction Stir Welding of AA6061-T6

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Conclusions l.jpg
Conclusions Immersed Friction Stir Welding of AA6061-T6

  • Submerged welds maintained 90-95% of parent UTS

  • Parent material UTS of 44.88 ksi compared well to the welded plate averaging UTS of ~41 ksi

  • Worm hole defect welds failed at 65% of parent UTS

    • effective dry weld equivalent tests not run

  • Optimal welds for IFSW required a weld pitch increase of 60%

  • Weld pitch of dry to wet optimal welds

    • Dry welds: wp = 2000/16 = 125 rev/inch

    • Wet welds: wp = 2000/10 = 200 rev/inch

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Summary and conclusions l.jpg
Summary and Conclusions Immersed Friction Stir Welding of AA6061-T6

  • Average torque increased from FSW to IFSW

    • FSW: 16 Nm

    • SFSW: 18.5 Nm

  • Optimal submerged (wet) FSW’s were compared to conventional dry FSW

  • Decrease in grain growth in the weld nugget due to inhibition by the fluid (water)

  • Water welds performed as well if not better than dry welds in tensile tests

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Acknowledgements l.jpg
Acknowledgements Immersed Friction Stir Welding of AA6061-T6

  • This work was supported in part by:

    • Los Alamos National Laboratory

    • NASA (GSRP and MSFC)

    • The American Welding Society

    • Robin Midgett for materials testing capabilities

    • UTSI for cross sectioning and microscopy

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


Future work l.jpg
Future Work Immersed Friction Stir Welding of AA6061-T6

  • Fracture Surface Microscopy

  • Hardness Testing for comparison

  • Further Mechanical testing

    • e.g. root bend tests

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA


References l.jpg
References Immersed Friction Stir Welding of AA6061-T6

  • Thomas M.W., Nicholas E.D., Needham J.C., Murch M.G., Templesmith P., Dawes C.J.:G.B. patent application No. 9125978.8, 1991.

  • Crawford R., Cook G.E. et al. “Robotic Friction Stir Welding”. Industrial Robot 2004 31 (1) 55-63.

  • Hofmann D.C. and Vecchio K.S. “Submerged friction stir processing (SFSP): An improved method for creating ultra-fine-grained bulk materials”. MS&E 2005.

  • Arbegast W. et al. “Friction Stir Spot Welding”. 6th International Symposium on FSW. 2006.

Materials Science & Technology 2007; September 16-20, 2007 — Detroit, MI, USA