The heterogeneous magnesium (Mg) matrix nanocomposite with dispersed soft phase exhibits high strength and toughness. Herein, the deformation behavior and failure process were investigated to reveal the unique mechanical behavior of the heterogeneous microstructure under compression. The extensive plastic deformation is accompanied by the flattening and tilting of the soft phase, inhibiting strain localization and leading to strain hardening. Moreover, a stable crack multiplication process is activated, which endows high damage tolerance to the heterogeneous Mg matrix nanocomposites. The final failure of the composite is caused by crack coalescence in the shear plane along a tortuous path. The presence of dispersed soft phases within the hard matrix induces a noticeable change in mechanical response. Especially, the malleability of the heterogeneous Mg matrix nanocomposite is two and ten times higher than that of pure Mg and the homogeneous Mg matrix nanocomposite, respectively. The current study provides a novel strategy to break the trade-off between strength and toughness in metal matrix nanocomposites.

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