friction stir welding after a decade of development

8/12/2019 friction stir welding after a decade of development

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By 1995, FSW had matured to a pointwhere it could be transitioned and imple-

mented into the U.S. aerospace and auto-motive markets. The many advantages ofFSW compared to conventional arc weld-ing have repeatedly been demonstratedwith both improved joint properties andperformance. Often, production costs aresignificantly reduced. Other times, FSWenables new product forms to be producedor skilled labor freed to perform othertasks. Research and development effortsover the last decade have resulted in im-provements in FSW and the spin-off of aseries of related technologies.

Introduction

In the 1920s and 1930s, arc welding re-placed rivets as the joining method forpressure vessels. Weld usage expandedthrough the 1940s with application tobuildings, structures, and ships. By 2006,arc welding has evolved into an interna-tional industry complete with welder ed-ucation and certification programs andgoverned by extensive specifications, de-

sign criteria, and standards. A 2002 sur-vey by the American Welding Society

(AWS) estimated that U.S. manufactur-ing industries spend more than $34.4 bil-lion annually on arc welding of metallicmaterials with an anticipated growth rateaveraging 5 to 15% per year. The con-struction, heavy manufacturing, and lightmanufacturing industries make up the ma-jority with $25 billion in annual expendi-tures. Industry-wide repair and mainte-nance of welded structures are estimatedto cost $4.4 billion annually. In doing so,these industries are a major consumer ofenergy and a producer of airborne emis-sions and solid waste.

Conventional arc welding of metalscreates a structural joint by local meltingand subsequent solidification. This nor-mally requires the use of expensive con-sumables, shielding gas, and filler metal.The melting of materials is energy inten-sive and solidifying metals are often sub-ject to cracking, porosity, and contamina-tion. Undesirable metallurgical changescan occur in the cast nugget due to alloy-ing with filler metals, segregation, and

thermal exposure in the heat-affectedzones. These may result in degraded jointstrengths, extensive and costly weld re-pairs, and unanticipated in-service struc-tural failures. Solid-state (nonmelting)joining avoids these undesirable charac-teristics of arc welding.

Implementation Incentives

Friction stir welding is one such non-melting joining technology that has pro-duced structural joints superior to conven-tional arc welds in aluminum, steel, nickel,

copper, and titanium alloys. Friction stirwelding produces higher strength, in-creased fatigue life, lower distortion, lessresidual stress, less sensitivity to corrosion,and essentially defect-free joints com-pared to arc welding. Since melting is notinvolved, shielding gases are not used dur-ing FSW of aluminum, copper, and NiAlbronze alloys while argon gas may be usedduring FSW of the higher-temperatureferrous and nickel alloys, mainly to pro-tect the ceramic and refractory pin toolsfrom oxidation. Simple argon environmen-tal chambers and trailing shields are used

during FSW of titanium alloys to minimizeinterstitial pickup and contamination. Ex-pensive consumables and filler metals arenot required. An excellent state-of-the-artreview of FSW technology is provided byMishra and Ma (Ref. 2).

Friction stir welding researchers andproducers (AJT, Inc.) estimate that if 10%of the U.S. joining market can be replacedby FSW, then 1.28 x 1013 Btu/year energy

Friction Stir WeldingAfter a Decade of Development

WILLIAM J. ARBEGAST ([email protected]) is director, NSF Center for Friction Stir Processing, South Dakota School ofMines and Technology, Rapid City, S.Dak. (http://ampcenter.sdsmt.edu).

Its not just welding anymore

BY WILLIAM J. ARBEGAS

Friction stir welding (FSW) is an innovative solid-state weldingprocess invented in 1991 by The Welding Institute (TWI) (Ref.1). Friction stir welding represents one of the most significant de-velopments in joining technology over the last half century. Theinitial development by TWI and its industrial partners under vari-ous Group Sponsored Projects focused on single pass, completejoint penetration of arc weldable (5XXX and 6XXX) and unweld-able (2XXX and 7XXX) aluminum alloys up to 1 in. thick.


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savings and 500 million lb/year green-house gas emission reductions can be re-alized. Hazardous fume emissions duringthe FSW of high-temperature andchromium-containing alloys are elimi-nated. Rockwell Scientific reports emis-sion levels of Cr, Cu, Mn, and Cr+6

(


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(BYU), and the University of Missouri-Rolla (UMR) together in a collaborativeFSW research program. The CFSP cur-rently has 22 government laboratory andindustrial sponsors. The center mission is

to perform advanced and applied re-search, develop design guidelines and al-lowables, train scientists and engineers,and transfer the FSW technology into abroader base within the industrial sector.

Current research programs at the CFSPinclude the following:

Design allowables and analysismethodologies for FSW beam and skinstiffened panel structures

Intelligent FSW process controlalgorithms

Thermal management of titaniumand aluminum FSW for property control

Microstructural modification of alu-minum and magnesium castings

FSW of HSLA and 4340 steels FSW of austenitic steels and Inconel

alloys Interactive database of FSW proper-

ties and processing parametersThe CFSP has also teamed with Iowa

State University Center for Nondestruc-tive Evaluations (CNDE) to assess the ef-fects of defects in aluminum alloy FSW.The probability of detection (POD) ofvarious nondestructive examinat ion(NDE) methods are being established forthe volumetric and geometric character-istic discontinuities and the relationship

between flaw size and reduction in staticstrength and fatigue life are being deter-mined. Statistical process control (SPC)methods are being developed based onprocess force and torque responses in fre-quency space and are being compared tothe POD of the NDE methods.

The Edison Welding Institute NavyJoining Center (NJC) has continued todevelop and demonstrate FSW technolo-gies in thick-section aluminum and tita-nium alloys for a variety of DOD applica-tions. One recent technology demonstra-tion program at the NJC used a combina-

tion of FSW, GMAW, and hybrid laserbeam welding to fabricate a large titaniumstructure from 0.50-in.-thick Ti-6Al-4Vplates Fig. 2. In this assembly, the ini-tial corner joints were friction stir weldedfrom the outside of the structure to estab-lish the basic shape, with the remainingstructure assembled using GMAW and hy-brid laser welding.

Under a recently completed DARPAprogram, Rockwell Scientific and theNAVSEA Carderock Surface WarfareCenter, in conjunction with 13 universityand industrial partners, performed exten-

sive development of friction stir process-ing on Al-, Cu-, Mn-, and Fe-based alloys.Within this program, MegaStir developedan advanced grade of polycrystalline cubicboron nitride (PCBN) capable of FSW offerrous alloys up to 0.500 in. thick Fig.3. The fracture toughness of the PCBN issufficiently high to allow features to bemachined on the tool pin, thus accommo-dating material flow around the tool to fillthe cavity in the tools wake.

Also, this same DARPA programdemonstrated the ability to friction stirprocess large areas on the surface of com-plex-shaped propellers using large indus-

Fig. 3 0.25 in. tapered with flats (left, bottom), 0.25-in. stepped spiral (le ft, top), and0.500-in. stepped spiral high-temperature PCBN FSW pin tools. Courtesy of MegaStir, Inc.

Fig. 4 Friction Stir Link, Inc., robotic FSW system processing large areas of NiAl bronzepropellers to remove near-surface casting defects. Courtesy of Rockwell Scientific.

Fig. 5 MTS ISTIR 10 friction stir weld system (left) with the Ameritherm 20-kW remoteheat station and induction preheating coil (right). Courtesy of South Dakota School ofMines.


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trial robotic FSW systems provided byFriction Stir Link, Inc. Fig. 4. Frictionstir processing eliminates near-surfacecasting discontinuities, increases the yieldstrength (>2X), and increases fatigue life(>40%) compared to as-cast NiAl bronze.In addition, FSW equipment manufactur-ers (General Tool Corp.) are exploring al-ternatives to high-cost multifunctionalFSW equipment by developing lower-cost, dedicated, single-purpose systems.

A new national FSW task coordinatedby Boeing is being launched under thenext-generation manufacturing technol-ogy initiative (NGMTI). The NGMTIprogram is designed to accelerate the de-velopment and implementation of break-through manufacturing technologies tosupport the transformation of the defenseindustrial base and to increase the globaleconomic competitiveness of U.S.-basedmanufacturing. This FSW task will bringtogether the DOD Tri-Services, JDMTP,DLA, FAA, NASA, and DOE with a largecontingent of industrial and university

partners to perform enabling and appliedresearch to correct overriding implemen-tation barriers, and, to perform ManTech-type demonstrations to accelerate indus-trial and government acceptance and im-plementation of friction stir welding.

A second NGMTI FSW task, coordi-nated by Friction Stir Link, Inc., in con-junction with the University of Wisconsin,is being developed to provide a low-mass,low-power, and high-mobility roboticFSW system. Friction Stir Link has beendeveloping robotic FSW and friction stirspot welding (described later) for a vari-

ety of automotive and commercial appli-cations. Integrating the FSW technologywith robotics allows for flexible manufac-turing approaches and reductions in pro-duction costs.

Concurrent Technologies Corp.(CTC), through the Navy ManTech Na-tional Metalworking Center (NMC), hasadvanced the development of FSW inthick-section 5083, 2195, and 2519 alu-minum for ground and amphibious com-bat vehicles. Several large-scale proto-types have been completed. The work byCTC and NMC has provided a valuable

transition of the technology from subscalelaboratory work to full-scale prototypeconstruction the last major step beforeproduction implementation.

Process Innovations

Innovations to the FSW process areongoing. Since 1995, more than 50 U.S.patents in FSW have been issued. Pin tooldesigns have evolved from those originallydeveloped by TWI to unique designs forthick-section, lap joint, high-temperature,and fast travel speed joining. For exam-

ple, in 2005, GKSS-GmbH reported that

Fig. 6 FSW process development tool at the Marshall Space Flight Center shown with a27-ft-diameter LH2barrel segment of the 2195 Al-Li Space Shuttle external tank (left). Full-scale LH2 tank (right) at the NASA Michoud Assembly Facility in New Orleans. Courtesyof NASA MSFC.

Fig. 7 The Eclipse 500 business class jet is currently in final FAA certification trials (left).The internal longitudinal and circumferential aluminum stiffeners (right, top) and windowand door doublers (right, bottom) are attached to the aluminum fuselage section with fric-tion stir welded lap joints. Courtesy of Eclipse Aviation.

Fig. 8 The friction stir welding equipment used to attach the stiffeners and doublers tothe Eclipse 500 fuselage sections was designed and fabricated by MTS Systems Corp. It iscapable of welding a variety of component geometries through the use of interchangeableholding fixtures located beneath the multiaxis FSW head and movable gantry frame. Cour-

tesy of Eclipse Aviation.


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successful FSW at welding speeds in ex-cess of 780 in./min in thin-gauge alu-minum butt joints had been achieved.

In 1999, NASA Marshall Space FlightCenter (MSFC) and the Boeing Co. de-veloped the retractable pin tool (Ref. 3)for FSW of tapered thickness joints. Mar-shall is currently investigating the use ofvery high rotation speed (>50,000 rpm)FSW, thermal stir welding (TSW), and theintegration of ultrasonic energy duringFSW to enable portable hand-held de-

vices. Other researchers are also evaluat-ing modifications to the FSW process. Forexample, the University of Missouri Columbia is evaluating electrically en-hanced friction stir welding (EEFSW)where additional heat is applied by resist-ance heating through the pin tool. TheUniversity of Wisconsin is developinglaser-assisted friction stir welding(LAFSW) of aluminum lap joints wherea laser is trained ahead of the pin tool topreheat the material.

Under a collaborative research pro-gram between the Army Research Labo-ratory (ARL) and the SDSMT AdvancedMaterials Processing and Joining Center(AMP), a variety of FSW technologies arebeing developed, including complex cur-vature FSW, friction stir spot welding(FSSW), dissimilar alloy FSW, low-cost fix-turing and tooling, and thick-plate titaniumand aluminum FSW. Prototypes of ad-vanced fuselage structures (Boeing), heli-copter beams (Sikorsky), and naval gun tur-ret weather shields (BAE Systems) havebeen built. The AMP Center is also devel-oping induction preheated friction stirwelding (IPFSW) using an Ameritherm20-kW remote heat station to preheatthick-plate aluminum, steel, cast iron, andtitanium alloys to increase travel speeds,reduce process forces, and reduce pin toolwear Fig. 5.

In 2001, MTS Systems Corp. patentedthe self-reacting pin tool technology (Ref.4). This innovation allows the FSW of ta-pered joints and eliminates the need for

back side anvil support to react the processloads. Lockheed Martin Space Systems andthe University of New Orleans NationalCenter for Advanced Manufacturing(NCAM) have demonstrated this self-reacting pin tool on the 27-ft-diameterdomes of the Space Shuttle external tank.In this application, multiple gore sectionsof 0.320-in.-thick 2195 Al-Li were joinedalong a simple curvature path to create thefull-scale dome assembly.

Industrial Implementations

The technology readiness level (TRL)for the FSW of aluminum alloys is highwith successful industrial implementationand space flight qualification by Boeingon the 2014 aluminum propellant tanksof the Delta II and Delta IV space launchvehicles. Lockheed Martin and NASAMSFC have developed and implementedFSW on the longitudinal welds of the 2195Al-Li liquid hydrogen and liquid oxygenbarrel segments of the external tank forthe Space Shuttle Fig. 6. LockheedMartin Missiles and Fire Control and theSDSMT have developed square box

beams for mobile rocket launch systemsthat are fabricated from thick-wall Csection extrusions joined by FSW to re-place the current hollow, square tube ex-trusions. Airbus has announced the use ofFSW in selected locations on the AirbusA350 and two new versions of the A340(A340-500, A340-600).

In 2000, the Air Force Metals Afford-ability Initiative (MAI) brought togethera consortium of industry and universitypartners to develop FSW for a variety ofDOD applications. Under Task 1, Joiningof Traditional Aluminum Assemblies,Lockheed Martin completed a develop-

Fig. 9 The central tunnel assembly of the Ford GT is a FSW assembly made from alu-minum stampings and extrusions. Courtesy of Ford Motor Co.

Fig. 10 Prototype pipe welding system showing external FSW head and internal mandrel

(inset). Courtesy of MegaStir, Inc.


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ment program that replaced the rivetedaluminum floor structure of the C130J airtransport with a FSW floor structure.Under Task 2, Joining of Complex Alu-minum Assemblies, Boeing developed aFSW cargo slipper pallet and imple-mented a FSW cargo ramp toenail on theC17 transport. The toenail is the onlyknown friction stir welded part flying ona military aircraft. Under Task 3, HardMetals Joining Development, the EdisonWelding Institute and the General Elec-tric Corp. (Engines Div.) developed high-temperature pin tools for the FSW ofsteel, titanium, and Inconel alloys foraircraft engine applications.

Eclipse Aviation is in final FAA certi-fication for the Eclipse 500 business classjet. First customer deliveries are sched-uled for 2006. Friction stir welded lapjoints are used as a rivet replacement tech-nology to join the longitudinal and cir-cumferential internal stiffeners to the aftfuselage section and to attach doublers atwindow and door cutout locations Fig.

7. The use of FSW eliminates the need forthousands of rivets and results in betterquality and stronger and lighter joints atreduced assembly costs. MTS SystemsCorp. designed and fabricated the customFSW equipment and production toolingfor Eclipse Aviation. This equipment per-mits welding complex curvatures overmany sections of the fuselage, cabin, andwing structures at travel speeds in excessof 20 in./min Fig. 8. Because the processis faster than more conventional mechan-ical joining processes, production cycletime is significantly reduced.

Over the last three years, the FordMotor Co. has produced several thousandFord GT automobiles with a FSW centraltunnel assembly Fig. 9. This tunnelhouses and isolates the fuel tank from theinterior compartment and contributes tothe space frame rigidity. The top alu-minum stamping is joined to two hollowaluminum extrusions along the length ofthe tunnel using a linear FSW lap joint.The use of FSW results in improveddimensional accuracy and a 30% increasein strength over similar GMA weldedassemblies.

The TRL for FSW of ferrous, stainlesssteel, nickel, copper, and titanium alloysis also high with a variety of full-scaledemonstration programs completed.MegaStir, Inc., has developed an im-proved grade of the polycrystalline cubicboron nitride (PCBN) high-temperaturepin tools (HTPT) that has shown an ac-ceptable service life for welding steels,nickel, and copper alloys.

In 2004, MegaStir, Inc., completed aprototype oil field pipeline FSW demon-stration program that successfully joined12-in.-diameter x 0.25-in. wall thicknessX-65 steel pipe segments using an auto-

mated internal mandrel and external FSWtooling system Fig. 10.

Chemical compatibility issues arisewhen welding titanium alloys with thePCBN pin tools. The University of SouthCarolina has shown the suitability of tung-sten-rhenium (W-Re) HTPT for most ti-tanium alloys. However, issues with pintool wear and excessive metal adhesionstill arise when welding Ti-6Al-4V. This is

possibly due to reactions between the rhe-nium in the pin tool and the vanadium al-loying elements in the titanium. Other re-fractory HTPT materials, such as tungsten-iridium (W-Ir), are under development atthe Oak Ridge National Laboratory.

In 2005, Lockheed Martin staff per-formed FSW on 0.20-in.-thick Ti-6Al-4Vsheets using dispersion-strengthenedtungsten HTPT that alleviated the stick-

Fig. 11 Joining of long lengths of contamination-free Ti-6Al-4V are possible with out ofchamber friction stir welding using shrouds and trail ing shoe shielding gas systems. Cour-tesy of Lockheed Martin Space Systems.

Fig. 12 Environmental chambers are used to provide an argon atmosphere and to mini-mize interstitial contamination in titanium FSW. Courtesy of South Dakota School of Mines.


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ing problem and allowed for many me-ters of welding Fig. 11. They reportthat the joint efficiency ranged from 98to 100% of base metal strength at testing

temperatures ranging from 320 to500F. Titanium FSW produced at theCFSP using custom-designed environ-mental chambers and an argon atmos-phere (Fig. 12) showed no evidence ofsurface discoloration or interstitial (O, N,and H) contamination.

Friction Stir Spot Welding

If FSW is considered as a controlledpath extrusion rather than a weldingprocess, several spin-off technologies canbe realized. Friction stir spot welding(FSSW) has been in development over

the last five years and has seen industrialimplementation as a rivet replacementtechnology. Currently, two variations toFSSW are being used. The plunge fric-

tion spot welding (PFSW) method waspatented by Mazda in 2003 (Ref. 5) andthe refill friction spot welding (RFSW)method was patented by GKSS-GmbH in2002 (Ref. 6).

In the Mazda PFSW process, a rotat-ing fixed pin tool similar to that used inlinear FSW is plunged and retractedthrough the upper and lower sheets of thelap joint to locally plasticize the metal andstir the sheets together. Even though thisapproach leaves a pull-out hole in the cen-ter of the spot, the strength and fatigue lifeis sufficient to allow application at reducedproduction costs on the Mazda RX-8 alu-

minum rear door structure Fig. 13.Since 2003, Mazda has produced morethan 100,000 vehicles with this PFSW reardoor structure. These PFSW doors pro-vide structural stability against side impactand impart five-star rollover protection.

The GKSS RFSW is being developedat the SDSMT AMP Center under licenseto RIFTEC-GmbH. This process uses a ro-tating pin tool with a separate pin andshoulder actuation system that allows theplasticized material initially displaced bythe pin to be captured under the shoulderduring the first half of the cycle and subse-quently reinjected into the joint during thesecond half of the cycle. This completelyrefills the joint flush to the surface Fig.14. In addition to development as a rivetreplacement technology for aerospacestructures, RFSW is also being developedas a tacking method to hold and restrainparts during welding by linear FSW.

Friction Stir Joining

Friction stir joining (FSJ) of thermo-plastic materials uses the controlled pathextrusion characteristics of the process tojoin 0.25-in.-thick sheets of polypropylene(PP), polycarbonate (PC), and high-density polyethylene (HDPE) materials.Recent work at Brigham Young Univer-sity has shown joint efficiencies for thesematerials ranging from 83% for PC to95% for HDPE and 98% for PP. Thesejoint efficiencies compare favorably withother polymer joining methods such as ul-trasonic, solvent, resistance, hot plate, andadhesive bonding. Current work at the

SDSMT AMP Center in collaborationwith the Air Force Research Laboratory -Kirtland is investigating the use of FSJ tojoin fiber-, particulate-, and nanoparticle-reinforced thermoplastic materials.

Friction Stir Processing

Friction stir processing (FSP) uses thecontrolled-path metalworking character-istics of the process to perform metallur-gical processing and microstructural mod-ification of local areas on the surface of apart. In 1997, FSP was used by Lockheed

Martin to perform microstructural modi-fication of the cast structure of 2195 Al-Li VPPA welds to remove porosity and hotshort cracks. This also improved room-temperature and cryogenic strength, fa-tigue life, and reduced the sensitivity tointersection weld cracking by crossingVPPA welds (Ref. 7).

In 1998, the DOE Pacific NorthwestNational Laboratory (PNNL) began in-vestigating the processing of SiC powdersinto the surfaces of 6061 aluminum to in-crease wear resistance. Initial studiesshowed that both SiC and Al2O3 could beemplaced into the surface of bulk materi-

Fig. 13 Use of the plunge friction spot welding (PFSW) method on the Mazda RX-8 reardoor structure provides for structural stability against side impact and five-star rollover pro-

tection at reduced production costs. Courtesy of Mazda Motor Corp.

Fig. 14 Refi ll friction spot welding (RFSW) using MTS ISTIR 10 sys tem and custom-designed head adapter (left). RFSW lap shear coupons (right, bottom) and metallurgicalcross section of RFSW showing complete joint penetration in 0.080-in.-thick 7075-T73 alu-minum (right, top). Courtesy of South Dakota School of Mines.


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als to create near-surface-graded MMCstructures. The University of Missouri-Rolla (UMR) has shown that a uniformSiC particle distribution can be achievedwith appropriate tool designs and tech-

niques, leading to significant increases insurface hardness.

In 2004, a PNNL/SDSMT AMP Cen-ter collaborative research program inves-tigated increasing the wear resistance ofheavy vehicle brake rotors by processingTiB2 particles into the surface of Class 40gray cast iron. This resulted in a fourfoldincrease in the dry abrasive wear resist-ance when tested per ASTM G65 Fig.15. PNNL and Tribomaterials, LLC haveperformed subscale brake rotor/pad weartests on FSP/TiB2 cast iron rotors. Thesesubscale brake tests have shown that

FSP/TiB2 processed brake rotors have im-proved friction characteristics and wearresistance over baseline heavy-vehiclebrake friction pairs.

Friction stir reaction processing(FSRP) was also investigated under thisPNNL/ SDSMT FSP/TiB2 program. Fric-tion stir reaction processing uses the hightemperatures and strain rates seen duringprocessing to induce thermodynamicallyfavorable in-situ chemical reactions on thesurface to a depth defined by the pin toolgeometry and metal flow patterns. Thisprovides an opportunity for innovativeprocessing methods to create new alloyson surfaces of materials and locally impart

a variety of chemical, mag-netic, strength, stiffness, andcorrosion properties.

Studies performed atthe University of Missouri-Rolla in conjunction withRockwell Scientific haveshown FSP to produce a finegrain size material and createlow-temperature, high-strain

rate superplasticity in alu-minum and titanium alloys.Pacific Northwest NationalLab is currently investigatingthe application of this FSP-in-duced superplasticity in thefabrication of large integrallystiffened structures.

Summary

Friction stir welding(FSW) has matured since itsintroduction into the U.S.market in 1995. The technol-

ogy readiness level for alu-minum alloys is high withseveral industrial implemen-tations. While developmentefforts and property charac-terizations have shown thatFSW can be used in ferrous,stainless, nickel, copper, andtitanium alloys, an industrial

champion is needed.The metalworking nature of the process

leads to the plunge (PFSW) and refill(RFSW) friction stir spot welding (FSSW)methods with properties comparable to riv-

eted and resistance spot welded joints. Theuse of friction stir processing (FSP) to lo-cally modify the microstructure of arc weldsand castings has been shown to increasestrength, improve fatigue life, and removedefects. Using FSP to stir particulate ma-terials into the surface has shown increasedwear resistance and creates particulate-re-inforced surface layers. Friction stir reac-tion processing (FSRP) can be used to cre-ate new materials and alloy combinationson part surfaces.

The higher-strength, nonmelting, andenvironmentally friendly nature of the

FSW process has shown cost reductionsin a variety of applications and has en-abled new product forms to be developed.Only a small percentage of the U.S. weld-ing and joining market has been targetedfor implementation. A variety of govern-ment, industry, and university collabora-tions are underway to accelerate the de-velopment and implementation of FSWand FSSW into these markets.

During the last decade, the defenseand aerospace sectors have taken the leadin implementing FSW. Recent advancesin pin tool designs and optimized process-

ing parameters have enabled FSW andFSSW applications in the marine, ground

transportation, and automotive indus-tries. Further innovations in low-costequipment and the development of indus-try standards, design guidelines, and atrained workforce will enable the intro-duction of FSW and FSSW into thebroader light manufacturing, heavy man-ufacturing, and construction industriesduring the next decade.

Acknowledgments

Contributions to this article were re-ceived from Gilbert Sylva and Mike Skin-ner (MTS Systems Corp.), Glenn Grant(PNNL), Brent Christner (Eclipse Avia-tion), Doug Waldron (AJT, Inc.), Jeff Ding(NASA MSFC), Tim Trapp (EWI), TracyNelson and Carl Sorensen (BYU), TonyReynolds (USC), Zach Loftus (LockheedMartin), Murray Mahoney (Rockwell Sci-entific), John Baumann (Boeing), Raj Tal-war (Boeing) , Dana Medlin (SDSMT),Anil Patnaik (SDSMT), Casey Allen(SDSMT), Rajiv Mishra (UMR), Chuck

Anderson (ATI, Inc.), John Hinrichs(Friction Stir Link, Inc.), Kevin Colligan(CTC Corp.), Scott Packer (MegaStir),and Tsung -Yu Pan (Ford Motor Co.).

The research programs at the Centerfor Friction Stir Processing (CFSP) areconducted by the faculty and students atthe SDSMT, BYU, UMR, and USC uni-versity sites and are funded under a grantfrom the National Science FoundationI/UCRC program office and the member-ship of the industrial and governmentpartners. The research programs at theSDSMT Advanced Materials Processing

and Joining Center are funded by theArmy Research Laboratory, Air ForceResearch Laboratory- Kirtland, DOE Pa-cific Northwest National Laboratory, andthe Edison Welding Institute.

References

1. Thomas, W .M. et al., Friction Stir ButtWelding, U.S. Patent No. 5,460,317.

2. Mishra, R.S., and Ma, Z.Y. 2005. Fric-tion stir welding and processing.Materials Sci-ence and EngineeringR50, pp. 178.

3. Ding, J., and Oelgoetz, P. 1999. Auto-

Adjustable Pin Tool for Friction Stir Welding,U.S. Patent No. 5,893,507.

4. Campbell, Fullen, and Skinner. 2001.Welding Head, U.S. Patent No. 6,199,745.

5. Iwashita, T. et al., 2003. Method andApparatus for Joining, U.S. Patent No.

6,601,751 B2.6. Schilling, C., and dos Santos, J. Method

and Device for Joining at Least Two AdjoiningWork Pieces by Friction Welding, U.S. Patent

Application 2002/0179 682.7. Arbegast, W. J., and Hartley, P. J. 2001.

Method of Using Friction Stir Welding to Re-pair Weld Defects and to Help Avoid Weld De-

fects in Intersecting Welds, U.S. Patent No.6,230,957.

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Fig. 15 Grade 40 gray cast iron ASTM G65 wear testresults. Friction stir processing TiB2particles into the sur-face resulted in a fourfold increase in ASTM G65 dry abra-sive wear resistance over that seen in samples without TiB2particles. Courtesy of South Dakota School of Mines.

friction stir welding after a decade of development

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