Influence of Friction Stir Processing on Mechanical Behavior of 2507 SDSS

Abstract

Duplex stainless steel (DSS) is used for desalination equipment, pressure vessels, marine applications, offshore applications, and in oil/gas plants where a highly corrosive environment is present. Super duplex stainless steel (SDSS) 2507 has excellent mechanical properties, such as high strength, high toughness, high fatigue life, and high corrosion resistance. Friction stir processing (FSP) is used to refine the grain structure of the processed region such that properties like strength, hardness, fracture toughness, fatigue life, and corrosion resistance are enhanced. In this paper, an optimized friction stir process of 2507 SDSS is carried out to refine the microstructure of the material in order to improve its mechanical properties. Microstructure analysis revealed that grains were refined from a size of around 160 µm in the base material to 2–30 µm in the processed zone. This grain size reduction resulted in improved strength, hardness, and fracture toughness of the material by up to 14%, 11%, and 12%, respectively. However, FSP has reduced the fracture strain by about 30%.

Friction Stir Processing Influence on Microstructure, Mechanical, and Corrosion Behavior of Steels: A Review

“…It can be observed from Figure 2 that a large reduction in grain size has been achieved from 160 μm in the base metal ( Figure 2 a) to 30 μm in the processed zone ( Figure 2 c). In addition, it can be seen that the grain size varies in the stir zone from the advancing side ( Figure 2 b) to the retreating side ( Figure 2 d), showing the heterogeneity of the grain structure in the processed region [ 16 ]. Table 1 summarizes the findings of different studies on the tensile behavior of steel after FSP/FSW.…”

“…As discussed above, FSP refines the grain structure, so it is expected to alter the fracture toughness of the processed material. Different researchers have examined the effect of FSP/FSW on the fracture toughness of different grades of steel and stainless steel material [ 16 , 41 , 42 , 43 , 44 , 45 ]. However, fracture toughness dependence on FSP parameters is still not very clear.…”

“… Typical microstructures of friction stir processed material: ( a ) base metal, ( b ) boundary of base metal and stir zone on advancing side, ( c ) stir zone, ( d ) boundary of base metal and stir zone on retreating side [ 16 ]. …”

“…All these factors have an impact on the behavior of the material as they influence the grain structure [ 15 ]. By refining the grain microstructure, mechanical properties such as strength, hardness, fracture toughness, fatigue behavior, wear, and corrosion resistance can be altered [ 16 , 17 , 18 ]. In this article, a comprehensive review is undertaken to investigate the influence of FSP on the behavior of steels.…”

Microstructure and Mechanical Properties of Friction Stir Welded 2205 Duplex Stainless Steel Butt Joints

“…The TMAZ has nearly the same feature microstructure as detected in both AS and RS. In the case of the DSS, both γ and α phases deform differently and recrystallize according to distinct kinetics [43,44]. The SZ (Figure 10) shows incomplete recrystallization of γ-phase, while the α-phase displays complete recrystallization and grain growth.…”