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 HV0.1, UTS = 370.2 MPa and At = 10.4%) was achieved using SLM parameters (P = 120 W, v = 500 mm/s and h = 45 μm). Microstructure was primarily constituted by quantities of fine equiaxed grains (i.e., α-Mg phase) and a small amount of β-Al12Mg17 structures (i.e., 4.96 vol%). Samples was dominated by a random texture with numerous spherical β-Al12Mg17 ([21¯1¯0]α// [111]β), long lath-like β-Al12Mg17 ([21¯1¯0]α// [11¯5]β and [1¯011]α// [32¯1¯]β), and 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.