Unveiling the impact of the effective particles distribution on strengthening mechanisms: A multiscale characterization of Mg+Y2O3 nanocomposites

C. Mallmann , F. Hannard (1) , E. Ferrie (2) , A. Simar (3) , R. Daudin (2) , P. Lhuissier (2) , A. Pacureanu (4) , Fivel Marc (2)

1 IMMC - Institute of Mechanics, Materials and Civil Engineering [Louvain]
2 SIMaP - Science et Ingénierie des Matériaux et Procédés
3 UCL - Université Catholique de Louvain = Catholic University of Louvain
4 ESRF - European Synchrotron Radiation Facility

Most models used to account for the hardening of nanocomposites only consider a global volume fraction of particles which is a simplified indicator that overlooks the particles size and spatial distribution. The current study aims at quantifying the effect of the real experimental particles spatial and size distribution on the strengthening of a magnesium based nanocomposites reinforced with Y 2 O 3 particles processed by Friction Stir Processing (FSP). X-ray tomographic 3-D images allowed to identify the best FSP parameters for the optimum nanocomposite. A detailed analysis indicates that the observed hardening is mainly due to Orowan strengthening and the generation of geometrically necessary dislocations (GND) due to thermal expansion coefficients (CTE) mismatch between magnesium and Y 2 O 3 particles. A multiscale characterization coupling 3D X-ray laboratory, synchrotron nanoholotomography and transmission electron microscopy (TEM) has been used to investigate particles size and spatial distribution over four orders of magnitude in length scales. Two dedicated micromechanical models for the two strengthening mechanisms are applied on the experimental particle fields taking into account the real particles size and spatial distribution, and compared to classical models based on average data. This required to develop a micromechanical model for CTE mismatch hardening contribution. This analysis reveals that the contribution from CTE mismatch is decreased by a factor two when taking into account the real distribution of particles instead of an average volume fraction.

Mots clés: Magnesium; nanocomposite; Friction Stir Processing (FSP); tomography; strengthening mechanisms

Domaines: Science des matériaux [cond-mat.mtrl-sci]

C. Mallmann, F. Hannard, E. Ferrie, A. Simar, R. Daudin, et al.. Unveiling the impact of the effective particles distribution on strengthening mechanisms: A multiscale characterization of Mg+Y2O3 nanocomposites. Materials Science and Engineering: A, 2019, 764, pp.138170. ⟨10.1016/j.msea.2019.138170⟩. ⟨hal-02270678⟩