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Nan Li1 Youxing Chen1 Xiang-Yang Liu1 Siddhartha Pathak2 Jian Wang3 Nathan Mara1

1, Los Alamos National Lab, Los Alamos, New Mexico, United States
2, University of Nevada, Reno, Reno, Nevada, United States
3, University of Nebraska, Lincoln, Lincoln, Nebraska, United States

Enhancing fracture toughness of Mg alloys has been actively investigated due to its huge potential as structural materials in the aerospace and automotive industries. However, Mg and its alloys, with a hexagonal close packed structure, present lacked ductility and poor deformability. Therefore, it is still challenging to improve the deformability while maintaining the high flow strength of Mg and Mg alloys. Here, we propose to use Mg/Nb laminated composites to enhance the fracture toughness, in which a high density of interfaces are designed and manufactured to enhance both the yield strength and ductility. The mechanical strength of the Mg/Nb multilayers measured from pillar compression achieve a high value of ~1.1 GPa. Besides such high strength, we also demonstrated such layered structure can enhance fracture toughness associated with highly activated basal slip and interface shearing between Mg and Nb interfaces. In situ three-point bending experiments have been performed in a SEM. Mg/Nb interfaces play a dominant role to block crack propagation and blunt crack tip. The stress concentration at crack tip is significantly released by shearing interfaces parallel to Mg basal planes. Along with the experimental observation, we also investigate the crack propagation in Mg/Nb by molecular dynamics.

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