Local microstructural characterization of an aged UR45N rolled steel: Application of the nanogauges grating coupled EBSD technique

Abstract : In the present article, metallic nanoparticles (NPs) used as nanogauges and electron backscattered diffraction (EBSD) are combined to investigate deformation mechanisms of the UR45 N duplex steel. The kinematic fields bring precious details in the evolution of the local deformation of austenitic and ferritic phases. The crystallographic information at the initial stage and in the plastic domain is obtained by the EBSD technique. Strain evolutions in each phase are analyzed. The first strain marks appear in austenite just before the elastoplastic transition. Slip and twinning activities in austenite constitute an important part of the work hardening of the material. The slips in ferrite are visible in the plastic domain and present complex geometry. The role of phase boundaries, which act as strain barrier is highlighted. The incompatibilities of deformations between the two phases modify the deformation mechanism of austenite in comparison with a pure austenitic stainless steel as 316 L. Local interactions between phases during the deformation are analyzed. The strong strain heterogeneities in the plastic domain are analyzed in the kinematic fields. Local evolutions of the deformation are also confronted to the macroscopic behavior of the material.