Nano-Deformation Behavior of a Thermally Aged Duplex Stainless Steel Investigated by Nanoindentation, FIB and TEM

Abstract

Nanoindentation and electron backscattering diffraction were conducted on a thermally aged duplex stainless steel to investigate the effect of crystal orientation on the plastic deformation behavior during indentation testing. Both nanohardness H and indentation modulus E are correlated with the orientation factor averaged over three normal directions of the contact surface. After thermal aging, the orientation dependence of the hardness and indentation modulus in ferrite significantly changed. For both the ferrite and austenite phases, the maximum and minimum values of the hardness and indentation modulus are given by the near- $$\left\langle {111} \right\rangle$$ and near- $$\left\langle {001} \right\rangle$$ -oriented grains, respectively. The TEM analysis results indicate that the area of plastic deformation in the ferrite grain decreases after thermal aging. The interactions between precipitates and dislocations are considered to be responsible for the degradation of plastic deformation ability in ferrite. The anisotropy of hardness is related to the crystallographic nature and shearing mechanisms.