Achieving ultra-high strength and ductility in Mg–9Al–1Zn–0.5Mn alloy via selective laser melting

Abstract

Fabrication of the Mg–9Al–1Zn–0.5Mn alloy with excellent mechanical performance using selective laser melting (SLM) technology is quite difficult owing to the poor weldability and low boiling point. To address these challenges and seek the optimal processing parameters, response surface methodology was systematically utilized to determine the appropriate SLM parameter combinations. Mg–9Al–1Zn–0.5Mn sample with high relative density (99.5 ​± ​0.28%) and favorable mechanical properties (microhardness ​= ​95.6 ​± ​5.28 HV_0.1, UTS ​= ​370.2 ​MPa, and A_t ​= ​10.4%) was achieved using optimized SLM parameters (P ​= ​120 ​W, v ​= ​500 ​mm/s, and h ​= ​45 ​μm). Sample ​is dominated by a random texture and microstructure is primarily constituted by quantities of fine equiaxed grains (α-Mg phase), a small amount of β-Al₁₂Mg₁₇ structures (4.96 ​vol%, including spherical: ${\left[2\overline{1}\overline{1}0\right]}_{\alpha }$// ${\left[111\right]}_{\beta }$ and long lath-like: ${\left[2\overline{1}\overline{1}0\right]}_{\alpha }$// ${\left[1\overline{1}5\right]}_{\beta }$ or ${\left[\overline{1}011\right]}_{\alpha }$// ${\left[3\overline{2}\overline{1}\right]}_{\beta }$), and some short rod-shaped Al₈Mn₅ nanoparticles. Benefiting from grain boundary strengthening, solid solution strengthening, and precipitation hardening of various nanoparticles (β-Al₁₂Mg₁₇ and Al₈Mn₅), high-performance Mg–9Al–1Zn–0.5Mn alloy biomedical implants can be fabricated. Precipitation hardening dominates the strengthening mechanism of the SLM Mg–9Al–1Zn–0.5Mn alloy.