Influence of composition and grain size on the damage evolution in MAX phases investigated by acoustic emission

In this study, the influence of the grain size and phase composition on damage mechanisms of Ti3SiC2-based materials are investigated. Commercially available and self-propagating high-temperature synthesized powders were sintered via spark plasma sintering and hot pressing methods. Materials with different amounts of Ti3SiC2 (from 52 to 72 wt%) and various mean grain sizes (from 8 to 20 mu m) were characterized by performing bending tests coupled with acoustic emission measurements. It permits to distinguish the involved damage mechanisms and their chronology in MAX phase-based materials. With the increase of the applied stress, damage begins with the onset of delaminations within MAX phase grains, then friction processes occur within previously formed microcracks, and finally (before rupture) new microcracks are generated due to the elasticity mismatch between phases. Increasing Ti3SiC2 content and grain size emphasizes the two first damage stages, and finally leads to a more pronounced nonlinear behavior.