Heterogeneous magnesium matrix nanocomposites with high bending strength and fracture toughness

Heterogeneous Mg matrix nanocomposites (Hetero-Mg-NCs) with different sizes/morphologies of soft phase were fabricated by planetary ball milling and subsequent hot-pressing sintering. The Hetero-Mg-NCs were subjected to non-notched and notched bending tests to investigate their bending behaviors. The results showed that high bending strength was successfully attained in the Hetero-Mg-NCs, especially the one with large soft phase exhibited a simultaneous improvement of bending strength and fracture toughness by 50% and 57.7%, respectively, compared with those of pure Mg. The fractography measurements revealed that the Hetero-Mg-NCs failed by a mixed-mode fracture. The abundant interfacial delamination cracks and micro-dimples were found in the Hetero-Mg-NC with large soft phase, indicating the enhancement of fracture toughness. By examining the crack propagation path, it was revealed that the Hetero-Mg-NC with large soft phase showed a longer zigzagging path, owing to the more profound crack tunneling, deflection and bifurcation phenomena. The results demonstrated that Mg–NCs with heterogeneous structure can simultaneously attain high strength and fracture toughness under bending loading.