TY - JOUR

T1 - Comparing the local-global deformation mechanism in different friction stir welding sequences of Ti-4Al-0.005B titanium alloy T-joints

AU - Su, Yu

AU - Li, Wenya

AU - Shen, Junjun

AU - Fu, Banglong

AU - dos Santos, Jorge F.

AU - Klusemann, Benjamin

AU - Vairis, Achilles

PY - 2021/8/17

Y1 - 2021/8/17

N2 - Titanium alloy T-joints were produced using two different friction stir welding (FSW) sequences, and the local-global deformation mechanisms until fracture were compared. Due to their differing FSW sequence characteristics, the optimal parameter ranges for the two T-joints are different. The stir zone (SZ) of the single-weld T-joint consists of lamellar α grains, while fine equiaxed α grains develop in the double-weld T-joint due to the selection of low heat input. Due to the different local microstructure zones in the joint, deformation inhomogeneity of the T-joint during tensile testing is observed. Independent of the welding sequence and for optimal process conditions, both T-joint configuration show nearly the same maximum tensile strength as the base material (BM), however at a relatively low fracture strain, below 20% of the BM. The local strain hardening rate in different zones of the T-joint was investigated. The strain hardening ability of SZ with fine grains is significantly higher than elsewhere, because the grain size contributes greatly to strain hardening behavior at low strain levels. The single-weld T-joint experienced a symmetric local strain distribution between advancing and retreating side. For the double-weld T-joint, there are significant differences between the first and the second weld area. The fracture morphologies of both T-joints are typical ductile, where the toughness of the single-weld joint is higher than that of the double-weld joint.

AB - Titanium alloy T-joints were produced using two different friction stir welding (FSW) sequences, and the local-global deformation mechanisms until fracture were compared. Due to their differing FSW sequence characteristics, the optimal parameter ranges for the two T-joints are different. The stir zone (SZ) of the single-weld T-joint consists of lamellar α grains, while fine equiaxed α grains develop in the double-weld T-joint due to the selection of low heat input. Due to the different local microstructure zones in the joint, deformation inhomogeneity of the T-joint during tensile testing is observed. Independent of the welding sequence and for optimal process conditions, both T-joint configuration show nearly the same maximum tensile strength as the base material (BM), however at a relatively low fracture strain, below 20% of the BM. The local strain hardening rate in different zones of the T-joint was investigated. The strain hardening ability of SZ with fine grains is significantly higher than elsewhere, because the grain size contributes greatly to strain hardening behavior at low strain levels. The single-weld T-joint experienced a symmetric local strain distribution between advancing and retreating side. For the double-weld T-joint, there are significant differences between the first and the second weld area. The fracture morphologies of both T-joints are typical ductile, where the toughness of the single-weld joint is higher than that of the double-weld joint.

KW - Deformation mechanism

KW - Friction stir welding

KW - Microstructure

KW - Strain hardening rate

KW - Tensile strength

KW - Titanium alloy T-joint

KW - Engineering

UR - http://www.scopus.com/inward/record.url?scp=85109560221&partnerID=8YFLogxK

U2 - 10.1016/j.msea.2021.141698

DO - 10.1016/j.msea.2021.141698

M3 - Journal articles

AN - SCOPUS:85109560221

VL - 823

JO - Materials Science and Engineering A

JF - Materials Science and Engineering A

SN - 0921-5093

M1 - 141698

ER -