  Open-porous scaffolds of WE43 Mg alloy with a body-center cubic cell pattern
were manufactured by laser powder bed fusion with different strut diameters.
The geometry of the unit cells was adequately reproduced during additive
manufacturing and the porosity within the struts was minimized. The
microstructure of the scaffolds was modified by means of thermal solution and
ageing heat treatments and was analysed in detail by means of X-ray
microtomography, optical, scanning and transmission electron microscopy.
Moreover, the corrosion rates and the mechanical properties of the scaffolds
were measured as a function of the strut diameter and metallurgical condition.
The microstructure of the as-printed scaffolds contained a mixture of Y-rich
oxide particles and Rare Earth-rich intermetallic precipitates. The latter
could be modified by heat treatments. The lowest corrosion rates of 2-3 mm/year
were found in the as-printed and solution treated scaffolds and they could be
reduced to ~0.1 mm/year by surface treatments using plasma electrolytic
oxidation. The mechanical properties of the scaffolds improved with the strut
diameter: the yield strength increased from 8 to 40 MPa and the elastic modulus
improved from 0.2 to 0.8 GPa when the strut diameter increased from 275 \mu m
to 800 \mu m. Nevertheless, the strength of the scaffolds without plasma
electrolytic oxidation treatment decreased rapidly when immersed in simulated
body fluid. In vitro biocompatibility tests showed surface treatments by plasma
electrolytic oxidation were necessary to ensure cell proliferation in scaffolds
with high surface-to-volume ratio.
