Achieving ultra-high strength and ductility in Mg–9Al–1Zn–0.5Mn alloy via selective laser melting
Cheng Chang, Hanlin Liao, Lin Yi, Yilong Dai, Sophie C. Cox, Ming Yan, Min Liu, Xingchen Yan
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 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: [21¯1¯0]α// [111]β and long lath-like: [21¯1¯0]α// [11¯5]β or [1¯011]α// [32¯1¯]β), 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.