Effect of Friction Stir Welding and Tempering on the Microstructure and Strength of a Tempformed Low-Alloy Steel

The microstructure developed in a low-alloy steel during friction stir welding and post-weld tempering was studied. The quenched steel samples were subjected to tempering at 650 °C for 1 h, followed by warm rolling to a total strain of 1.5 at the same temperature. The processed steel samples were ch...

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Bibliographic Details
Published in:Metals (Basel ) 2024-01, Vol.14 (1), p.114
Main Authors: Dolzhenko, Anastasiia S., Lugovskaya, Anna S., Malopheyev, Sergey, Dudko, Valeriy, Tikhonova, Marina, Kaibyshev, Rustam, Belyakov, Andrey
Format: Article
Language:English
Subjects:
Alloys
Boron steel
Elongation
Friction stir welding
Grain boundaries
Grain size
Hardness
high-strength low-alloy steel
Low alloy steels
Martensite
Mechanical properties
Microstructure
Software
Specialty metals industry
Specialty steels
Steel
Steel alloys
Steel plates
strength and plasticity
Temperature
Tempering
tempforming
Ultrafines
Warm rolling
Warm working
Welded joints
Welding
Yield strength
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Summary:The microstructure developed in a low-alloy steel during friction stir welding and post-weld tempering was studied. The quenched steel samples were subjected to tempering at 650 °C for 1 h, followed by warm rolling to a total strain of 1.5 at the same temperature. The processed steel samples were characterized by an ultrafine-grained microstructure of the lamellar type with a transverse grain size of 360 nm and exhibited an yield strength of about 1200 MPa and a total elongation of 13%. Then, the steel plates were joined by friction stir welding. The yield strength of the weld joint was about 1170 MPa, although the total elongation decreased to 1.5%. The martensite microstructure, with a high-angle grain boundary spacing of about 800 nm, was developed in the stir zone. This martensite in the stir zone originated from the ultrafine-grained prior austenite, resulting in an almost two-fold increase in hardness as compared to the base material. Tempering of the welded sample at 650 °C for 1 h resulted in a decrease in the hardness of the weld joint to the level of the base material. Nevertheless, the fracture of the welded and tempered sample occurred in the base material. The yield strength of the welded sample after tempering was 930 MPa, with a total elongation of 13%.
ISSN:2075-4701
2075-4701
DOI:10.3390/met14010114