Using hierarchical composite approach to improve mechanical response of Mg and Mg–Bi2O3 nano-composites

Novel Mg nano-composites reinforced with either Bi2O3 nano-particles or hybrid Al–Bi2O3 particles (Bi2O3 nano-particles hybridized with Al using ball milling) have been synthesized, in this work, through powder metallurgy route using microwave assisted rapid sintering technique followed by hot extrusion. Compared to monolithic Mg, the Mg/xBi2O3 (x (vol.%) = 0.22, 0.66 and 1.11) nano-composites displayed higher strength while failure strain was compromised. Midst the diverse nano-composites formulations, the Mg/0.22Bi2O3 nano-composite revealed the best overall enhancement in tensile yield strength (0.2% YS), compressive yield strength (0.2% CYS), ultimate tensile strength (UTS) and ultimate compressive strength (UCS) (up to +24%, +9.0%, +28%, and +39%, respectively) compared to pure Mg while both tensile and compressive failure strain (FSt, FSc) remained statistically the same. To improve the mechanical response of Mg/xBi2O3 nano-composites further, the Bi2O3 nano-particles were hybridized with Al to outcome hybrid Al–Bi2O3 particles. Hybridizing Bi2O3 nano-particles with Al (Al–Bi2O3) and getting embedded in Mg matrix discovered a remarkable mechanical response enhancement in the case of hierarchical Mg/0.92Al–xBi2O3 configurations compared to their Mg/xBi2O3 nano-composites equivalents. Selectively, an enhancement of +27% (0.2%YS), +39% (0.2%CYS), +21% (UTS), +31% (UCS) and +33% (FSt) was witnessed in the case of hierarchical Mg/0.92Al–0.22Bi2O3 configuration compared to its Mg/0.22Bi2O3 nano-composite equivalent whereas FSc remained statistically the same. Here, some of the strengthening mechanisms that might be accountable for the notable mechanical response enhancement of Mg nano-composites owing to presence of Bi2O3 nano-particles, either solely or as the hybridized form, have been classified. The effect of both as received Bi2O3 nano-particles and hybrid Al–Bi2O3 particles on textural evolution of Mg nano-composites is also scrutinized in this work.