Novel Mg composite was fabricated to explore the synergetic effect of GNPs and MgOs on the microstructure evaluation, deformation behavior and mechanical properties of Mg–Sr–Ca alloy. The addition of hybrid reinforcement into the Mg–Sr–Ca alloy led to considerable grain refinement (53%). The GNPs were homogeneously dispersed in the matrix alloy where they were randomly distributed revealing the pulling out and pulling off performance. The MgOs were accumulated on the surface of GNPs as a result of the synergetic effect of 1 + 1<2 of hybrid reinforcement by Orowan and thermal mismatch strengthening mechanisms. The yield strength of the hybrid composite at both tensile and compressive tests was improved 19.5% and 38.9% respectively. Significantly synergetic effect of hybrid reinforcement was presented by improvement of failure strain at both tensile and compressive tests (86.5% and 20.4%, respectively) due to grain refinement and reduction of eutectic phase (85%). Conversion of detwinning into the dominant slip mechanism in tensile loading and reduction of twin boundaries motion in compressive loading due to addition of hybrid reinforcement resulted hardening phenomena. Also, the Mg–Sr–Ca/GNP + MgO composite illustrated a low corrosion rate in the SBF solution. Comparative plot indicated that novel composites can be considered for the wide range of applications.

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