Study on Special Deformation Mechanism of 2205 Duplex Stainless Steel During Expansion Test

Expansion tube technology is important in supporting the oil drilling industry. The 2205 duplex stainless steel exhibits excellent corrosion resistance, offers superior mechanical properties, and demonstrates good expansion material in the downhole. During the expansion process, the deformation mechanism and grain orientation of 2205 duplex stainless steel were analyzed using TEM and EBSD. The stress state soft coefficient was used to compare the expansion and tensile states, which revealed that the expansion stress state was not conducive to plastic deformation. Further, microstructure analysis showed that α phase in 2205 duplex stainless steel consists of a body-centered cubic structure, its deformation mechanism was dislocation slip, and dislocation density was low. The γ phase consists of a face-centered cubic structure, and its deformation mechanism was twinning-induced plasticity, which is the major contribution region of plastic deformation. The comparison of the Taylor factor of the two phases showed that the γ phase is the “soft phase” and the α phase is the “hard phase,” and the deformation of the γ phase preferentially occurs during the expansion process. The grain orientation of the α phase after the expansion was <110>, while the grain orientation of the γ phase after the expansion was <111>.