Effect of copper addition on tensile behavior in Fe-Cr-Ni stable austenitic stainless steel

Effects of Cu on tensile properties and deformation mechanisms were investigated in the stable Fe-Cr-Ni austenitic stainless steel with different wt% of Cu. Addition of Cu slightly decreased the yield strength and negligibly affected the ultimate tensile strength, while it induced a considerably large reduction of fracture elongation. Deformation twins were generated during the tensile deformation, and fraction of deformation twins decreased with increasing Cu content. However, degree of twinning was similar, regardless of Cu content, at the same tensile strain, which indicated that development of twins was interfered by earlier fracture triggered by Cu addition and hardly contributed to different hardening behavior at the early stage of deformation. Cu significantly altered the motion of dislocations. The low-Cu-containing alloy mainly developed tangled dislocations and cellular structures, whereas the high-Cu-containing alloy did planar slip and high density of dislocation walls. Although the addition of Cu decreased the shear modulus and increased the stacking fault energy, dislocation substructure changed from tangled to planar slip with increasing Cu content. This indicated that slip planarity of high-Cu-containing alloys might be originated from the formation of short-range ordering or clustering, thereby leading to the local stress concentration and reduction of the elongation.