Experimental and numerical investigation of key microstructural features influencing the localization of plastic deformation in Fe-TiB2 metal matrix composite

摘要

A new generation of iron-based matrix composite reinforced by TiB2 particles was deformed in tension to investigate at a mesoscopic scale the localization of plastic deformation in relation with characteristic microstructural features of the composite (in particular, ferrite grain boundaries and particle/matrix interfaces). Large electron back-scattered diffraction (EBSD) maps with improved angular resolution were acquired to evaluate statistically the evolution of the geometrically necessary dislocation (GND) density from the early stage of the deformation. GNDs were found to accumulate preferentially at matrix/particle interfaces with hot-spots located at the tips of elongated particles. Additional length-scale parameters derived from EBSD data evidenced the key influence of two main microstructural features: the particle morphology and the particle clustering. Finally, we present results of an advanced full-field micromechanical model that is best suited to capture these effects, based on an enhanced crystal plasticity elasto-viscoplastic Fast Fourier Transform (EVP-FFT) formulation coupled with a phenomenological continuum Mesoscale Field Dislocation Mechanics (MFDM) theory. By taking the experimental TiB2 particle distribution into account, the model describes qualitatively the observed effect of particle morphological features on the heterogenous distribution of GNDs.