Microstructural and mechanical properties of AZ31 magnesium alloy with Cr addition and CO2 incorporation during processing

AZ31 Mg-alloy with ∼5 wt.% Cr and incorporated with CO2 during processing were produced using the disintegrated melt deposition technique. The effect of Cr addition and CO2 incorporation on the microstructural and mechanical properties was investigated after extrusion.Microstructural investigation revealed that the addition of Cr (AZ31–5Cr) significantly refined the grain size, and the incorporation of CO2 (AZ31–5Cr–CO2) resulted in the in situ formation of chromium carbide (Cr23C6) phase. The evaluation of mechanical properties indicated that when compared to the AZ31 base alloy, both AZ31–5Cr and AZ31–5Cr–CO2 showed significant improvement in the strength properties. Based on the structure–mechanical properties correlation, it was identified that in AZ31–5Cr, Cr acted as a metallic reinforcement that improved the hardness, tensile and compressive yield strengths. In AZ31–5Cr–CO2, the in situ formed Cr23C6 phase acted as a strengthening phase and enhanced the mechanical properties, which were significantly higher than those of AZ31 base alloy and AZ31–5Cr.

► AZ31 Mg-alloy with ∼5 wt.% Cr and CO2 incorporation was produced using DMD method.
► Bottom pouring in disintegrated melt deposition method eliminated entry of oxides.
► Cr addition refined the grain size and improved the mechanical properties of AZ31–5Cr.
► Incorporation of CO2 formed in situ Cr23C6 phase in AZ31–5Cr–CO2.
► AZ31–5Cr–CO2 (in situ composite) with Cr23C6 showed the best mechanical properties.