Surface roughness of duplex steels: role of the microstructure

Forged duplex steels possess a highly anisotropic two-phase microstructure. Due to the mismatch of the coefficients of thermal expansion thermal stresses evolve during cyclic thermal loading which can lead to plastification of one or both phases. While the macroscopic deformation of specimens is well understood, open questions related to the effect of traction free surfaces still remain. Experimental evidence is found for a characteristic evolution of the surface roughness depending on the microstructure of the material. In this work micromechanical models based on a continuum mechanical description of the phase domains are evaluated with respect to surface roughness. Parameters for the description of the amplitude and the anisotropy of surface deformations are proposed and the model predictions are compared with experimental results.