Influence of Mg content on microstructure and mechanical properties of the bio-inspired porous aluminum

Inspired by poplar wood microstructure, this paper proposes and prepares a novel bio-inspired porous aluminum with hierarchical pore structure and bi-directional composition-graded structure. The hierarchical pore structure consists of millimeter-sized large pores from hollow Al tubes and micrometer-sized small pores from sintered Al/Mg powder. This study comprehensively examines the effect of Mg content on the microstructure and mechanical properties of the bio-inspired porous aluminum. The results show that the phase of porous aluminum transforms from the single-phase Al (Mg) solid solution to the dual phase consisting of Al (Mg) solid solution and Al 3 Mg 2 intermetallic compound as Mg content increases. The aluminum with 15 wt.% Mg achieves optimal metallurgical bonding at interfaces between powder particles and between powder and tube walls. A bidirectional concentration-graded distribution of Mg is formed in the tube walls due to the synergistic evaporation-diffusion effect of Mg, with the solid solubility of Mg peaks in the Al-15 wt.% Mg alloy — exhibiting concentrations of 12.53 wt.% (outer wall), 2.35 wt.% (tube wall core), and 10.43 wt.% (inner wall), respectively. However, alloys with higher Mg additions result in the formation of substantial intermetallic compounds in the powder zone and on the tube wall surface. The compression results show that the anisotropic structure endows better out-of-plane compression and energy absorption performance than the in-plane direction. Overall, porous aluminum with 15 wt.% Mg exhibits optimal mechanical properties, with the most numerous and deepest dimples formed during fracture.