Effect of dislocation channeling on void growth to coalescence in FCC crystals

Abstract

The effect of dislocation channeling - a heterogeneous deformation mode at the grain scale observed in irradiated, quenched or heavily cold-worked materials - on void growth to coalescence in Face-Centered-Cubic (FCC) crystals is investigated experimentally. Solution Annealed 304L austenitic stainless steel is used as a model FCC material, in a reference state or irradiated with protons in order to trigger dislocation channeling deformation mode. Micrometric cylindrical voids drilled using Focused Ion Beam (FIB) technique at the grain scale in thin tensile samples subjected to uniaxial stress loading conditions allows a detailed description of void growth and coalescence. Compared to the reference state where plasticity appears homogeneous at the void scale, dislocation channels strongly interact with voids at the irradiated state, especially at low applied strain where characteristic localization patterns are observed and described. As applied strain increases, deformation becomes more and more homogeneous at the void scale through gradual activation of secondary channels. Numerical simulations based on FCC crystal plasticity constitutive equations are performed and compared to experiments. The main experimental features are recovered by the numerical simulations, but discrepancies remain for both reference and irradiated states. Ductile fracture modeling in materials exhibiting dislocation channeling is finally discussed based on these experimental and numerical results.