Enhanced mechanical response of hybridized magnesium nano-composites as a function of strain rate

Abstract

Background: In this work, hybrid Mg/Al-CNT nano-composites were fabricated utilizing a powder metallurgy route followed by a microwave-assisted rapid sintering technique and hot extrusion. Hybrid reinforcements (ball milled Al-CNT particles) comprising different contents of CNTs coated with fixed amounts of Al were used for strengthening. Objective: The mechanical response of hybrid Mg/Al-CNT nano-composites as a function of strain rate was investigated. Method: Tensile and compressive tests for monolithic Mg along with hybrid Mg/Al-CNT nano-composites at quasi-static and dynamic regimes were carried out using: (i) an MTS servohydraulic testing machine and (ii) a Split-Hopkinson Pressure Bar (SHPB) apparatus with an average strain rate of 10¯⁴ s¯¹ and 2×10³ s¯¹, respectively. Considering the crystallographic texture, the different mechanical responses of Mg due to the presence of hybrid Al-CNT particles as a function of strain rate under both tension and compression is differentiated here. Results: The hybrid Mg/Al-CNT nano-composites exhibited slightly smaller average matrix grain sizes compared to monolithic Mg and a reasonable hybrid Al-CNT particles distribution. The presence of hybrid Al-CNT particles weakens the basal texture and accentuates the prismatic texture (basal plane orientation parallel to ED) compared to the monolithic pure Mg which contributes to strengthening the hybrid Mg/Al-CNT nano-composite compared to monolithic Mg. It was also observed that the tremendous increase in strain rate led to a considerable increase in flow stress of monolithic Mg along with hybrid Mg/Al-CNT nano-composites under both tension and compression. Conclusions: During the tension test at both high and low strain rates, prismatic slip is the main deformation mechanism, leading to alignment of the directions with the tensile axis and to a spread of the basal plane parallel to the tensile axis. Tensile twinning is enhanced at high strain rates and remains the predominant deformation mechanism during the early stages of deformation in compression tests.