FSW: Variants

Explanations, Acronyms, Abbreviations and Trademarks of Friction Stir Welding and its Variants

The following acronyms are used in various publications on friction stir welding and its variants. Some of them have a double-meaning:


FSC — Friction Stir Channelling

FSC — Friction Stir Channeling: (a) Specifications on probe thread profile for FSC of a  AA5083-H111 plate (dimensions in mm); (b) The assembled FSC-tool with shoulder and probe; (c) Clamping jig used for the making FSC samples in the laboratory[1]

© Heikki Karvinen , Afshin Hasani Aleni, Pauli Salminen , Tatiana Minav and Pedro Vilaça, CC BY 4.0 


Friction Stir Channelling (FSC) is a solution for producing internal closed channels along a desired path with a constant or continuously modified shape along the path in a single manufacturing step. The channels are formed by continuous extraction of part of the plasticised workpiece material into the external flash.[1]


FSC  Friction Stir Channeling: Macrograph of the cross-section of the channel with the metallurgical zones of interest: 1—top corner of retreating side, 2—middle part of the ceiling, 3—top corner of the advancing side, 4—bottom corner of the advancing side, 5—middle part of the bottom and 6- bottom corner of the retreating side[1]

© Heikki Karvinen , Afshin Hasani Aleni, Pauli Salminen , Tatiana Minav and Pedro Vilaça, CC BY 4.0 


FSE — Friction Stir Extrusion

FSE — Friction Stir Extrusion of ultra-thin wall biodegradable magnesium alloy tubes[18]

© Vasanth C. Shunmugasamya, Eisha Khalida, Bilal Mansoor, CC BY 4.0 


Friction stir extrusion (FSE) was used in 2020/21 to produce thin-walled biodegradable tubes, which corrode from the outside after being implanted into the body of a human or animal. Biodegradable tubular structures such as stents are routinely deployed for various short-term medical interventions. The biodegradability can eliminate the need for secondary procedures associated with conventional stents.[18] 


The coronary stents manufacture require defect-free, high-quality tubes with thin walls (0.1 mm – 1 mm) as a precursor. Fully consolidated, structurally sound ultra-thin walled (∼ 400 μm) AZ31 Mg alloy tubes by friction stir back extrusion (FSE) — a process used typically to manufacture thick metallic tubes and rods.[18]


The tube cross-sectional microstructure was layered and consisted of a severely deformed stir zone with refined grains near the inner edge, a back-extruded zone with small grains near the outer edge, and a thermomechanically affected zone (TMAZ) with coarse grains develop within the central region. The inner tube surface microstructure had an average grain size of 4.1 ± 1.9 μm and a strong basal texture. In comparison, the outer tube surface microstructure was coarse, with an average grain size of 13.3 ± 6.4 μm with no preferred orientation.[18]


Upon exposure to Hank’s balanced salt solution at 37 °C, microgalvanic coupling resulting from the gradient through-the-thickness grain size and texture differences between the tube inner and outer surfaces, and residual strain arising from the FSE process, promoted a localized attack that preferentially initiated on the outer tube surface and progressed inwards. The study established that FSE is a viable single-step process to manufacture ultra-thin Mg alloy tubes suitable for degradable precision tubular applications.[18]


PFSW* — Plasma Assisted Friction Stir Welding

PFSW — Plasma Assisted Friction Stir Welding with a 500kg payload COMAU robot NJ5000, a bespoke FSW spindle and a Hyperterm Powermax 1250® 80 A plasma cutter
PFSW — Plasma Assisted Friction Stir Welding with a 500kg payload COMAU robot NJ5000, a bespoke FSW spindle and a Hyperterm Powermax 1250® 80 A plasma cutter

PFSW — Plasma Assisted Friction Stir Welding with a 500kg payload COMAU robot NJ5000, a bespoke FSW spindle and a Hyperterm Powermax 1250® 80 A plasma cutter

© Bruno Silva Cota (UNIFEI) and Alexandre Queiroz Bracarense (UFMG), CC BY-NC 4.0


Experimental trials were conduced in Brasil on using Plasma Assisted Friction Stir Welding (PFSW*) for dissimilar material combinations of joining 3 mm thick SAE 1020 carbon steel sheets to 3 mm thick 5052 H34 aluminum sheets using an offset of 0 or -2.5 mm. The plasma torch was used to preheat the steel to 250 °C, 350 °C or 450 °C. Further parameter development trials are recommended to improve the weld quality and reduce tool wear.[19]


PFSW* — Pinless Friction Stir Welding

PFSW — Pinless Friction Stir Welding[13]

© Yu Ni, Yue Mao, Dingqiang Qin, Xuan Xiao and Li Fu (Xi’an, China), CC BY 4.0


Pinless Friction Stir Welding (PFSW*) was used for instance by Zhenlei Liu et al in 2016 for making thin wall structures from Alclad 2A12-T4 alloy.[14] Yu Ni et al later conducted successfully a study on μFSW of 0.5 mm thick AA7075-T6 sheets with a thickness of 0.5 mm in Xi’an, China in the butt joint configuration. The influence of the welding process on the thermal cycles and deformations of μFSW was systematically studied through experiments. They concluded that "in comparison to the pin tool, the joint fabricated by the pinless tool experienced a lower peak temperature, a shorter elevated-temperature exposure time, and a larger temperature gradient within the shoulder range under the same shoulder penetration depth."[13]


Reciprocating FSW

Reciprocating friction stir welding is particularly useful for welding plastics, as shown in the first patent of Wayne Thomas at TWI[8]

Courtesy of TWI Ltd.


RFSW — Robotic Friction Stir Welding

Closed-loop temperature control can be used in Robotic Friction Stir Welding (RFSW) for modifying the spindle rotation speed to maintain a constant welding temperature. For industrial applications this will reduce the programming time and increase the robustness of the process. By measuring the ohmic resistance between the tool and the work piece it is possible to assess the processing temperature without the need for thermocouples inside the tool. The method can be used used to control both plunging and welding.[25][26]


Industrial application of Robotic Friction Stir Welding (RFSW)

Industrial application of robotic FSW

© SAPA, CC BY 2.0 


RT-FSW — Combined Rotation and Translation of the Tool Axis (commonly known as Com-stir™)

Wayne Thomas, the inventor of friction stir welding, developed and published also
Com-stir™, a compound motion for FSW and machining, using a rotary motion in combination with an orbital motion.[6]


The benefits of this motion have been confirmed by several researchers, and Cabibbo et al. described this as an "approach in which welding pin was forced to slightly deviate away from the joining centreline (defined by authors as RT)", i.e. an "innovative approach to the conventional FSW process, defined by authors as RT-type configuration, in which the welding motion of the pin tool was obtained by combining two different movements occurring simultaneously:[12][13]


(i) the rotation of the pin axis around an axis, perpendicular to the sheet blanks and belonging to the welding line, with a radius equal to R, and

(ii) the translation of the pin axis along a direction parallel to the welding line."[12]  


UAFSW — Ultrasonically Assisted FSW

UAFSW — Ultrasonically assisted friction stir welding concept and device[10, retouched]

© Zhiqiang Zhang, Changshu He, Ying Li, Jingxun Wei, Menggang Zhai, Su Zhao and Xiang Zhao, CC BY 4.0


Ultrasonic vibration promotes the flow of metal at the interface, enlarged the size of the stirred zone (SZ), and reduced the angle between the hook defect and the interface. It was observed that, under otherwise identical conditions, UAFSLW joints can withstand a greater fracture shear strength than FSLW joints, as ultrasonic vibration helps to mix the material at the interface, thus, enlarging the SZ and diminishing the cold lap defects.[10]


Viblade™ Welding — In-line Reciprocating FSW

Viblade™ Welding — In-line Reciprocating Friction Stir Welding: Schematic, photo and macrosections of some of the first welds made in 9 mm thick polypropylene sheet

Courtesy of TWI Ltd.


VFSW — Vortex Friction Stir Welding

VFSW — Vortex Friction Stir Welding: Principle, tool and shematic side view

© Xiaochao Liu, Yunqian Zhen, Zhikang Shen, Haiyan Chen, Wenya Li, Wei Guo and Zhufeng Yue, CC BY 4.0


For Vortex Friction Stir Welding (VSFW) the tool is partially made from the same material as the workpiece material. The process depends on a vortex material flow to make the weld. The weld macro- and micro-structures look similar to those of conventional FSW. However, in VSFW a lug boss is left at the end of the weld instead of an exit-hole as in conventional FSW. The mechanical properties are similar or even identical to those in conventional FSW.[24]


VFSW — Vortex Friction Stir Welding: Metallographic section of lug boss at end of  weld

© Xiaochao Liu, Yunqian Zhen, Zhikang Shen, Haiyan Chen, Wenya Li, Wei Guo and Zhufeng Yue, CC BY 4.0


Acronyms Related to Friction Stir Welding and its Variants and Derivatives (non-exhaustive)

  • AFSD  Additive Friction Stir Deposition 
  • AFSW*  Autogenous Friction Stir Welding
  • AFSW*  Assisted Friction Stir Welding (hybrid)
  • BFSW  Bobbin Friction Stir Welding
  • CFSW  Cooled Friction Stir Welding
  • DFSW  Dissimilar Friction Stir Welding
  • DP-FSSW  Double-side Probeless Friction Stir Spot Welding[36] 
  • DS-FSW  Double Side Friction Stir Welding
  • EAFSW  Electrically Assisted Friction Stir Welding**
  • EFSW  Electrically Assisted Friction Stir Welding**
  • FBJ  Friction Bit Joining[2]
  • FFSW  Filling Friction Stir Welding
  • FMB  Friction Melt Bonding[2]
  • FSADW  Friction Stir Assisted Diffusion Welding[2] 
  • FSAM  Friction Stir Additive Manufacturing[30] 
  • FSB  Friction Stir Brazing[2]
  • FSBR  Friction Stir Blind Rivetting[38]   
  • FSC*  Friction Stir Chanelling[1][21][22]
  • FSC*  Friction Stir Clinching[28]
  • FSD  Friction Stir Dovetailing[2]  
  • FSE  Friction Stir Extrusion[2] 
  • FSLW  Friction Stir Lap Welding[20]
  • FSP  Friction Stir Processing
  • FSpW — Friction Spot Welding[39] 
  • FSS welding  friction stir scribe welding
  • FSSAW  Friction Stir Spot Adhesive Welding[33] 
  • FSSFW  Friction Stir Spot Fusion Welding[2] 
  • FSSW  Friction Stir Spot Welding
  • FSW  Friction Stir Welding
  • GFSW  Gas Torch (assisted) Friction Stir Welding  
  • GTAFSW  Gas Tungsten Arc (assisted) Friction Stir Welding
  • HFSC  Hybrid Friction Stir Channeling[24]
  • HFSW  Hybrid Friction Stir Welding[2]
  • HSFSW — High rotation speed friction stir welding[42]
  • IFSW  Impulse Friction Stir Welding
  • i-FSW  Induction heating tool assisted Friction Stir Welding 
  • IPFSW — Induction Preheated Friction Stir Welding[32]  
  • LFSW  Laser assisted Friction Stir Welding 
  • LFSW  Linear Friction Stir Welding (used as a synonym for FSW)[14] 
  • LAFSW — Laser Assisted Friction Stir Welding 
  • M-FSW — Multi-pass friction stir processing[41]
  • MPT — Multi-Pin Tool
  • MFSW  Modified Friction Stir Welding
  • µFSW  Micro Friction Stir Welding
  • NFSW  Normal Friction Stir Welding
  • OFSW  Orbital Friction Stir Welding
  • RFSJ — Refill Friction Spot Joining[36]  
  • PFSW*  Penetrating Friction Stir Welding
  • PFSW*  Pinless Friction Stir Welding
  • PFSW*  Plasma Friction Stir Welding[19]  
  • PFSW*  Portable Friction Stir Welding[9] 
  • QFSW  Heat input of Friction Stir Welding 
  • RAFSW  Right Angle Friction Stir Welding[16]  
  • RFSW  Robotic Friction Stir Welding[25][26]  
  • RFSSW — Refill Friction Stir Spot Welding[40] 
  • RT-FSW — Rotation and Translation of the Tool Axis (Com-stir™)  
  • SBT tunneling  Submerged bobbin tool (SBT) tunneling[43] 
  • SFSW  Submerged Friction Stir Welding
  • SSCA FSW — Stationary Shoulder Corner Angle Friction Stir Welding
  • SSFSW  Stationary Shoulder Friction Stir Welding
  • SSFSC  Stationary Shoulder Friction Stir Chanelling[31] 
  • SRFSLW  Self-Riveting Friction Stir Lap Welding[17]
  • SRFSW  Self Reacting Friction Stir Welding
  • TFSWBs  Tailor Friction Stir Welded Blanks
  • T-FSW — FSW of T-joints[29]
  • TSW  Thermal Stir Welding
  • UAFSW  Ultrasonically Assisted Friction Stir Welding 
  • UAFSLW  Ultasonically Assisted Friction Stir Lap Welding[20]
  • UFSW  Underwater Friction Stir Welding
  • USE-FSW  UltraSound Enhanced Friction Stir Welding[44]
  • VFSW  Vortex Friction Stir Welding[24]

Trademarks Related to Friction Stir Welding and its Variants and Derivatives (non-exhaustive)

  • ESAB: Legio standardized and modular FSW machines
  • ESAB: Rosio™  FSW robots
  • ESAB: SuperStir™  Custom-built FSW machinery
  • Mazak: MegaStir™  Machines, tools and consulting services for FSW
  • PaR Systems: AdAPT™   Adaptable Adjustable Pin Tool
  • PTG Holyrod: PowerStir™  Solution provider for high-strength FSW machines
  • Stirlink: RoboStir™  Robotic FSW
  • Stirtec: MaXstir™  FSW tools that are characterized by high functionality, process reliability, high wear resistance and associated high tool life
  • TWI: Com-stir™ — Compound motion for FSW and machining, using a rotary motion in combination with an orbital motion[6]
  • TWI: CoreFlow™  A Sub-Surface Machining Process
  • TWI: MX-Triflute™  Multihelix FSW tool 
  • TWI: Pro-stir™ — Near-Net Shaped Manufacture by FSW[5]
  • TWI: Re-stir™  FSW with reversal of the direction of the tool rotation, which is imposed after one or more revolutions[7]
  • TWI: Skew-stir™  FSW method in that the axis of the tool is given a slight inclination (skew) to that of the machine spindle (also: A-Skew™ probe)[7]
  • TWI: Stir-lock™  An ‘in-process’ forge/forming seam joining technique[5]
  • TWI: Twin-stir™ —  Using two FSW tools either parallely side-by-side transverse to the welding direction or tandem in-line with the welding direction or staggered to ensure the edges of the weld regions partially overlap[7]
  • TWI: Viblade™  Friction Stir Welding (in-line reciprocating FSW)[3[4]
  • TWI: Whorl™  Frustum-shaped probe with a logarithmic spiral like a nautilus
  • Wichita State University: Wiper™  Tool shoulder with ridge around the scrolls[25]

* Ambiguity (Double Meaning)

* Acronyms marked with an asterisk are synonymously used for several variants, and their use is therefore disencouraged without an explanation. The P in the acronym PFSW can, for instanstance, be interpreted as penetrating, pinless, plasma or portable. 

** Some variants can be abreviated by several acronyms, e.g. EFSW and EAFSW for Electrically Assisted Friction Stir Welding.



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