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

Abstract

A new generation of iron-based matrix composite reinforced by TiB 2 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 inter-faces). 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 TiB 2 particle distribution into account, the model describes qualitatively the observed effect of particle morphological features on the heterogenous distribution of GNDs.

A combined EBSD/nanoindentation study of dislocation density gradients near grain boundaries in a ferritic steel

“…This angular resolution can be determined from the local misorientation distribution or "Kernel Average Misorientation" (KAM) in an undeformed material [25]. Following [4], the angular resolution is defined by the 0.95 percentile of the cumulative KAM distribution function. Figure 3a represents the empirical cumulative distribution of the KAM angle, computed from the 8 nearest neighbors, and derived from the raw orientation data acquired on the Al-killed ferritic undeformed sample.…”

“…On the one hand, the EBSD technique alone was already used to identify such microstructural internal lengths induced by plastic deformation [2,3]. For instance, Genée et al [4] recently investigated the localization of plastic deformation in a deformed FeTiB2 composite under uniaxial tension using high-resolution 2D-EBSD. Internal lengths were analyzed calculating the average density of GNDs as a function of distances to the closest TiB2 particles, ferrite grain boundaries, particle tips and ferrite triple points.…”

Study on the precipitation mechanisms of TiC particles in steel matrix composites fabricated by eutectic solidification

“…Hadjem-Hamouche [17] found that the fracture of large-scale primary TiB 2 is a main reason for the failure of high-modulus steel during a three-point bending deformation process. Genée [18] characterized the evolution of the geometrically necessary dislocation density distributions in high modulus steel during tensile deformation by Electron Backscatter Diffraction (EBSD), proving that the generation of local plastic deformation is mainly caused by the tips of slender particles and large-sized particles. These results indicate that the key factors limiting the performance levels of eutectic composites are eutectic particles rather than bonding interfaces.…”