Evolution of microstructure and crystallographic texture during dissimilar friction stir welding of duplex stainless steel to low alloy structural steel

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Abstract

Electron backscatter diffraction (EBSD) was used to analyze the evolution of microstructure and crystallographic texture during friction stir welding of dissimilar type 2205 duplex stainless steel (DSS) to type S275 low alloy structural steel. The results of microstructural analyses show that the temperature in the center of stirred zone reached temperatures between Ac1 – Ac3 during welding, resulting in a minor ferrite to austenite phase transformation in the S275 steel, and no changes in the fractions of ferrite and austenite in the DSS. Temperatures in the thermo-mechanically affected and shoulder affected zones of both materials, in particular towards the root of the weld, did not exceed the Ac1 of S275 steel. The shear generated by the friction between the material and the rotating probe occurred in austenitic/ferritic phase field of the S275 and DSS. In the former the transformed austenite regions of the microstructure was transformed to acicular ferrite, on cooling, while the dual phase austenitic/ferritic structure of the latter was retained. Studying the development of crystallographic textures with regard to shear flow lines generated by the probe tool, showed the dominance of simple shear components across the whole weld in both materials. The ferrite texture in S275 steel was dominated by D1, D2, E, ¯E and F where the fraction of acicular ferrite formed on cooling showed a negligible deviation from the texture for the ideal shear texture components of bcc metals. The ferrite texture in DSS was dominated by D1, D2, J, ¯Jand F, and that of austenite was dominated by the A, ¯A, B and ¯B of the ideal shear texture components for bcc and fcc metals, respectively. While D1, D2 and F components of the ideal shear texture are common between the ferrite in S275 steel and that of dual phase DSS, the preferential partitioning of strain into the ferrite phase of DSS led to the development of J and ¯J components in DSS, as opposed to E and ¯E in the S275 steel. The formation of fine and ultra-fine equiaxed grains was observed in different regions of both materials that are believed to be due to strain induced continuous dynamic recrystallization (CDRX) in ferrite of both DSS and S275 steel, and discontinuous dynamic recrystallization (DDRX) in austenite phase of DSS.
LanguageEnglish
Pages664-687
Number of pages24
JournalMetallurgical and Materials Transactions A
Volume50
Issue number2
Early online date29 Nov 2018
DOIs
StatePublished - 11 Jan 2019

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friction stir welding
Friction stir welding
Steel
Stainless Steel
Ferrite
stainless steels
ferrites
Stainless steel
textures
Textures
steels
microstructure
Microstructure
austenite
Austenite
shear
Dynamic recrystallization
Welds
Metals
Cooling

Keywords

  • friction stir welding
  • continuous dynamic recrystallization
  • discontinuous dynamic recrystallization
  • duplex stainless steel
  • dissimilar welding

Cite this

@article{9326e1f4144142d2ae953dd437f59a4e,
title = "Evolution of microstructure and crystallographic texture during dissimilar friction stir welding of duplex stainless steel to low alloy structural steel",
abstract = "Electron backscatter diffraction (EBSD) was used to analyze the evolution of microstructure and crystallographic texture during friction stir welding of dissimilar type 2205 duplex stainless steel (DSS) to type S275 low alloy structural steel. The results of microstructural analyses show that the temperature in the center of stirred zone reached temperatures between Ac1 – Ac3 during welding, resulting in a minor ferrite to austenite phase transformation in the S275 steel, and no changes in the fractions of ferrite and austenite in the DSS. Temperatures in the thermo-mechanically affected and shoulder affected zones of both materials, in particular towards the root of the weld, did not exceed the Ac1 of S275 steel. The shear generated by the friction between the material and the rotating probe occurred in austenitic/ferritic phase field of the S275 and DSS. In the former the transformed austenite regions of the microstructure was transformed to acicular ferrite, on cooling, while the dual phase austenitic/ferritic structure of the latter was retained. Studying the development of crystallographic textures with regard to shear flow lines generated by the probe tool, showed the dominance of simple shear components across the whole weld in both materials. The ferrite texture in S275 steel was dominated by D1, D2, E, ¯E and F where the fraction of acicular ferrite formed on cooling showed a negligible deviation from the texture for the ideal shear texture components of bcc metals. The ferrite texture in DSS was dominated by D1, D2, J, ¯Jand F, and that of austenite was dominated by the A, ¯A, B and ¯B of the ideal shear texture components for bcc and fcc metals, respectively. While D1, D2 and F components of the ideal shear texture are common between the ferrite in S275 steel and that of dual phase DSS, the preferential partitioning of strain into the ferrite phase of DSS led to the development of J and ¯J components in DSS, as opposed to E and ¯E in the S275 steel. The formation of fine and ultra-fine equiaxed grains was observed in different regions of both materials that are believed to be due to strain induced continuous dynamic recrystallization (CDRX) in ferrite of both DSS and S275 steel, and discontinuous dynamic recrystallization (DDRX) in austenite phase of DSS.",
keywords = "friction stir welding, continuous dynamic recrystallization, discontinuous dynamic recrystallization, duplex stainless steel, dissimilar welding",
author = "S. Rahimi and Konkova, {T. N.} and I. Violatos and Baker, {T. N.}",
year = "2019",
month = "1",
day = "11",
doi = "10.1007/s11661-018-5023-3",
language = "English",
volume = "50",
pages = "664--687",
journal = "Metallurgical and Materials Transactions A",
issn = "1073-5623",
number = "2",

}

TY - JOUR

T1 - Evolution of microstructure and crystallographic texture during dissimilar friction stir welding of duplex stainless steel to low alloy structural steel

AU - Rahimi,S.

AU - Konkova,T. N.

AU - Violatos,I.

AU - Baker,T. N.

PY - 2019/1/11

Y1 - 2019/1/11

N2 - Electron backscatter diffraction (EBSD) was used to analyze the evolution of microstructure and crystallographic texture during friction stir welding of dissimilar type 2205 duplex stainless steel (DSS) to type S275 low alloy structural steel. The results of microstructural analyses show that the temperature in the center of stirred zone reached temperatures between Ac1 – Ac3 during welding, resulting in a minor ferrite to austenite phase transformation in the S275 steel, and no changes in the fractions of ferrite and austenite in the DSS. Temperatures in the thermo-mechanically affected and shoulder affected zones of both materials, in particular towards the root of the weld, did not exceed the Ac1 of S275 steel. The shear generated by the friction between the material and the rotating probe occurred in austenitic/ferritic phase field of the S275 and DSS. In the former the transformed austenite regions of the microstructure was transformed to acicular ferrite, on cooling, while the dual phase austenitic/ferritic structure of the latter was retained. Studying the development of crystallographic textures with regard to shear flow lines generated by the probe tool, showed the dominance of simple shear components across the whole weld in both materials. The ferrite texture in S275 steel was dominated by D1, D2, E, ¯E and F where the fraction of acicular ferrite formed on cooling showed a negligible deviation from the texture for the ideal shear texture components of bcc metals. The ferrite texture in DSS was dominated by D1, D2, J, ¯Jand F, and that of austenite was dominated by the A, ¯A, B and ¯B of the ideal shear texture components for bcc and fcc metals, respectively. While D1, D2 and F components of the ideal shear texture are common between the ferrite in S275 steel and that of dual phase DSS, the preferential partitioning of strain into the ferrite phase of DSS led to the development of J and ¯J components in DSS, as opposed to E and ¯E in the S275 steel. The formation of fine and ultra-fine equiaxed grains was observed in different regions of both materials that are believed to be due to strain induced continuous dynamic recrystallization (CDRX) in ferrite of both DSS and S275 steel, and discontinuous dynamic recrystallization (DDRX) in austenite phase of DSS.

AB - Electron backscatter diffraction (EBSD) was used to analyze the evolution of microstructure and crystallographic texture during friction stir welding of dissimilar type 2205 duplex stainless steel (DSS) to type S275 low alloy structural steel. The results of microstructural analyses show that the temperature in the center of stirred zone reached temperatures between Ac1 – Ac3 during welding, resulting in a minor ferrite to austenite phase transformation in the S275 steel, and no changes in the fractions of ferrite and austenite in the DSS. Temperatures in the thermo-mechanically affected and shoulder affected zones of both materials, in particular towards the root of the weld, did not exceed the Ac1 of S275 steel. The shear generated by the friction between the material and the rotating probe occurred in austenitic/ferritic phase field of the S275 and DSS. In the former the transformed austenite regions of the microstructure was transformed to acicular ferrite, on cooling, while the dual phase austenitic/ferritic structure of the latter was retained. Studying the development of crystallographic textures with regard to shear flow lines generated by the probe tool, showed the dominance of simple shear components across the whole weld in both materials. The ferrite texture in S275 steel was dominated by D1, D2, E, ¯E and F where the fraction of acicular ferrite formed on cooling showed a negligible deviation from the texture for the ideal shear texture components of bcc metals. The ferrite texture in DSS was dominated by D1, D2, J, ¯Jand F, and that of austenite was dominated by the A, ¯A, B and ¯B of the ideal shear texture components for bcc and fcc metals, respectively. While D1, D2 and F components of the ideal shear texture are common between the ferrite in S275 steel and that of dual phase DSS, the preferential partitioning of strain into the ferrite phase of DSS led to the development of J and ¯J components in DSS, as opposed to E and ¯E in the S275 steel. The formation of fine and ultra-fine equiaxed grains was observed in different regions of both materials that are believed to be due to strain induced continuous dynamic recrystallization (CDRX) in ferrite of both DSS and S275 steel, and discontinuous dynamic recrystallization (DDRX) in austenite phase of DSS.

KW - friction stir welding

KW - continuous dynamic recrystallization

KW - discontinuous dynamic recrystallization

KW - duplex stainless steel

KW - dissimilar welding

UR - https://link.springer.com/journal/volumesAndIssues/11661

U2 - 10.1007/s11661-018-5023-3

DO - 10.1007/s11661-018-5023-3

M3 - Article

VL - 50

SP - 664

EP - 687

JO - Metallurgical and Materials Transactions A

T2 - Metallurgical and Materials Transactions A

JF - Metallurgical and Materials Transactions A

SN - 1073-5623

IS - 2

ER -