Micro/nano-reinforcements in bimodal-grained matrix: A heterostructure strategy for toughening particulate reinforced metal matrix composites

To overcome strength-ductility trade-off in particulate metal matrix composites (PRMMCs), we developed a novel and controllable strategy, for the first time, via a combination of micro/nano-reinforcements and ultrafine/ coarse-grained (UFG/CG) matrices. A powder assembly was developed to fabricate micro B4Cp/6061Al composites, which features UFG/CG matrices containing ex/in-situ nano dispersoids and exhibits superior combination of strength and ductility. It was found that such a novel architecture possesses both intrinsic and extrinsic toughening. As the intrinsic toughening mechanisms, enhanced dislocation storage capability of UFG regions, twinning, and hetero-deformation induced toughening were detected. Moreover, crack-deflection induced by nano dispersoids as well as crack-blunting at UFG/CG regions were considered as the main extrinsic toughening mechanisms. The proposed strategy can be applied to design the architecture of other PRMMCs with both high strength and high ductility. Aluminum alloys; Powder processing; Heterostructures; Particulate reinforced composites; Microstructural toughening

Automated summary

In this study, a novel strategy combining micro/nano-reinforcements and ultrafine/coarse-grained matrices was developed to achieve a balance between strength and ductility in particulate metal matrix composites (PRMMCs). The proposed architecture exhibits both intrinsic and extrinsic toughening mechanisms, and can be applied to design other high strength and high ductility composites.