TY - JOUR

T1 - Semi-stationary shoulder bobbin-tool

T2 - A new approach in tailoring macrostructure and mechanical properties of bobbin-tool friction stir welds in magnesium alloy

AU - Li, Gaohui

AU - Chen, Ting

AU - Fu, Banglong

AU - Shen, Junjun

AU - Bergmann, Luciano

AU - Zhou, Li

AU - Chen, Ke

AU - Santos, Jorge F. dos

AU - Klusemann, Benjamin

N1 - Funding Information: The research was sponsored by the National Natural Science Foundation of China (Grant No. 51974100 and 52075330 ), the China Postdoctoral Science Foundation (Grant No. 2022M722048 ) and China Scholarship Council Doctoral Joint-Training Program (No. 202006120198 ). Publisher Copyright: © 2023 Elsevier B.V.

PY - 2023/8/1

Y1 - 2023/8/1

N2 - Bobbin tool friction stir welding has high process flexibility and is particularly suitable for closed structures such as hollow extrusions or pipes. More recently, a bobbin tool concept having one rotating and one stationary shoulder has been proposed. The present investigation developed this novel semi-stationary shoulder concept to bobbin tool friction stir welding of magnesium alloy for the first time. The concept was proved to be feasible by decoupling the upper shoulder from the rotation of the bobbin tool. Holding the upper shoulder stationary during welding led to reduced handling forces as well as torque, enabling higher welding speeds up to 1500mm/min. This speed is 50% larger than the value achieved by the standard tool concept, which makes the semi-stationary shoulder variant more attractive for industrial applications. Furthermore, holding the upper shoulder stationary modified the original symmetrical refilling of the plasticized metal into an asymmetrical pattern. In case of improper welding parameters being employed, the asymmetrical refilling led to transportation of created volumetric defects close to the upper surface from the mid-thickness and thus facilitated visual inspection of the weld. In the proper sets of welding parameters, the joints produced by the semi-stationary shoulder variant experienced lower level of strain localization during tensile testing than those produced by the standard variant. The weakened strain concentration led to an enhancement of the joint elongation from 82% to 95% of that of the base metal. Data availability All data included in this study are available upon reasonable request by contacting the first author.

AB - Bobbin tool friction stir welding has high process flexibility and is particularly suitable for closed structures such as hollow extrusions or pipes. More recently, a bobbin tool concept having one rotating and one stationary shoulder has been proposed. The present investigation developed this novel semi-stationary shoulder concept to bobbin tool friction stir welding of magnesium alloy for the first time. The concept was proved to be feasible by decoupling the upper shoulder from the rotation of the bobbin tool. Holding the upper shoulder stationary during welding led to reduced handling forces as well as torque, enabling higher welding speeds up to 1500mm/min. This speed is 50% larger than the value achieved by the standard tool concept, which makes the semi-stationary shoulder variant more attractive for industrial applications. Furthermore, holding the upper shoulder stationary modified the original symmetrical refilling of the plasticized metal into an asymmetrical pattern. In case of improper welding parameters being employed, the asymmetrical refilling led to transportation of created volumetric defects close to the upper surface from the mid-thickness and thus facilitated visual inspection of the weld. In the proper sets of welding parameters, the joints produced by the semi-stationary shoulder variant experienced lower level of strain localization during tensile testing than those produced by the standard variant. The weakened strain concentration led to an enhancement of the joint elongation from 82% to 95% of that of the base metal. Data availability All data included in this study are available upon reasonable request by contacting the first author.

KW - Friction stir welding

KW - Semi-stationary shoulder bobbin tool

KW - Magnesium alloy

KW - Welding characteristics

KW - Texture

KW - Deformation behavior

KW - Engineering

UR - http://www.scopus.com/inward/record.url?scp=85152886597&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/f10b7bd6-ca41-331b-8c1a-9aa81d4f76ea/

U2 - 10.1016/j.jmatprotec.2023.117984

DO - 10.1016/j.jmatprotec.2023.117984

M3 - Journal articles

VL - 317

JO - Journal of Materials Processing Technology

JF - Journal of Materials Processing Technology

SN - 0924-0136

M1 - 117984

ER -