Electron Backscatter Diffraction Investigation of Heat Deformation Behavior of 2205 Duplex Stainless Steel

Abstract

Duplex stainless steel is special because it contains two phases, namely, ferrite and austenite, which endow the duplex stainless steel the advantages of good strength, ductility, and corrosion resistance. On account of its excellent performance, it is widely used in fields as diverse as petroleum transportation, energy industry, marine industry, etc. [1][2][3] Different from that of general single-phase materials, the matrix of duplex stainless steel is always two phase in the process of processing. Ferrite and austenite show varying features in the deformation process of duplex stainless steel due to differences in the lattice structure, element content, and atomic diffusion ability between the two phases, and consequently obvious uneven deformation takes place. [4] At the same time, the high-stacking fault energy of ferrite renders the climbing and slipping of its dislocations easier, thereby leading to the occurrence of dynamic recovery (DRV). [5] On the contrary, the DRV of austenite is constrained due to its low-stacking fault energy, and dynamic recrystallization (DRX) has thus become its main softening mechanism. [3,4] In addition, the recrystallization features of the two phases differ remarkably. Ma [5] mentioned that when low-angle grain boundaries (LAGBs) continuously absorbed the dislocations caused by plastic deformation in ferrite, LAGBs rotated and increased gradually to form high-angle grain boundaries (HAGBs). The study found that the recrystallization of ferrite grains was characterized by continuous dynamic recrystallization (CDRX), whereas that of austenite showed the feature of discontinuous dynamic recrystallization (DDRX) (austenite grains nucleated in the high-energy region, mainly along grain boundaries, followed by the growth of new grains). Mozumder [6] also claimed that the recrystallization mechanisms of the ferrite and austenite phases of duplex lightweight steel were CDRX and DDRX, respectively. However, the softening mechanism of both ferrite and austenite was found to be the conversion from LAGBs to HAGBs in the study of Liu, [7] proving that the recrystallization mechanism of both phases was CDRX. The effect of ferrite on the recrystallization behavior of austenite in duplex stainless steel was investigated by Dehghan-Manshadi, [8] who believed that CDRX was the result of subgrain boundary coalescence and the softening mechanism of austenite. In fact, texture also has an important influence on the evolution of microstructure. Gao [9] found that γ-fiber has a higher Taylor factor in Ultra Purified 17% Cr Ferritic Stainless Steels, so it has higher storage energy than α-fiber, leading to preferred nucleation in grains with γ-fiber orientations during annealing. Moura [10] reported that the texture and recrystallization evolution in ferrite are

Comparison Study of Hot Deformation Behavior and Microstructure Evolution of Rack Steels with and without Segregation

“…According to Figure 11, the substructures were the main components at the strain rate of 0.01 s −1 (Figure 11a,c), while the deformed microstructures accounted for the largest proportion at the strain rate of 1 s −1 (Figure 11b,d). As the strain rate increases, it is conducive to recrystallization and nucleation due to the large dislocation gradient and high storage energy near the bowed grain boundaries, and [ 15,32,33 ] the subgrains can coalesce by absorbing dislocations until the grain boundary becomes HAGBs. As a result, the low‐angle grain boundarys are converted to HAGBs and finally the grains are refined.…”

“…Therefore, considering the strong relationship between deformation mechanism and deformation conditions, it is significantly vital to understand the hot deformation behavior of segregated and nonsegregated zones for the rack steels to optimize the hot workability and rolling process. Numerous studies of the hot deformation behavior have been conducted based on flow curves and constitutive relationships in magnesium alloys, [10][11][12] stainless steels, [13][14][15] microalloyed steels, [16][17][18] and so on. However, the effect of segregation on the hot deformation behavior is rarely reported for ultraheavy steel plates.…”

A Comparative Study of Three Constitutive Models concerning Thermo-Mechanical Behavior of Q345 Steel during Hot Deformation

“…Meanwhile, the flow stress continues to increase, and no steady-state stress appears. These two curves with different changing trends reflect that Q345 steel undergoes different degrees of dynamic recrystallization during hot deformation at different strain rates [14]. As shown in Figure 2a-c, at the same temperature, the increase of strain gradually lowers the flow stress and eventually stabilizes because the softening effect produced by dynamic recovery gradually offsets the work hardening that resulted from the dislocation proliferation effect.…”

“…Meanwhile, the flow stress continues to increase, and no steadystate stress appears. These two curves with different changing trends reflect that Q345 steel undergoes different degrees of dynamic recrystallization during hot deformation at different strain rates [14].…”

Hot Compression Behavior of 18Cr–11Mn–0.06Ni–0.19N High‐Mn Ultralow Nickel Duplex Stainless Steel under Large Deformation

“…However, due to various effects generated within the material and the external environment during the hot deformation, the flow curves obtained by the experiment cannot well reflect the hot deformation behavior under the expected deformation parameters. For instance, even though the experiments have ensured that the sample contact surfaces are sufficiently lubricated, the stress rise caused by friction cannot be ignored under large deformation conditions [26]. In addition, only about 3-5% of the energy of plastic deformation remains in the material as stored energy during plastic deformation, and a significant amount of deformation energy is released by raising the temperature of the test specimen [27].…”