Influence of heat treatment on microstructure, mechanical and corrosion behavior of WE43 alloy fabricated by laser-beam powder bed fusion

WE43 parts with favorable forming quality are fabricated by laser-beam powder bed fusion and the interaction between laser beam and powder is revealed.After suitable heat treatment, the anisotropic microstructure is eliminated, with nano-scaled Mg24Y5 particles homogeneously precipitated.The yield strength and ultimate tensile strength are improved to (250.2 +/- 3.5) MPa and (312 +/- 3.7) MPa, respectively, while the elongation still maintains at high level of 15.2%.Homogenized microstructure inhibits the micro galvanic corrosion and promotes the development of passivation film, thus decreasing the degradation rate by an order of magnitude.The porous WE43 scaffolds offer a favorable environment for cell growth. Magnesium (Mg) alloys are considered to be a new generation of revolutionary medical metals. Laser-beam powder bed fusion (PBF-LB) is suitable for fabricating metal implants with personalized and complicated structures. However, the as-built part usually exhibits undesirable microstructure and unsatisfactory performance. In this work, WE43 parts were firstly fabricated by PBF-LB and then subjected to heat treatment. Although a high densification rate of 99.91% was achieved using suitable processes, the as-built parts exhibited anisotropic and layered microstructure with heterogeneously precipitated Nd-rich intermetallic. After heat treatment, fine and nano-scaled Mg24Y5 particles were precipitated. Meanwhile, the alpha-Mg grains underwent recrystallization and turned coarsened slightly, which effectively weakened the texture intensity and reduced the anisotropy. As a consequence, the yield strength and ultimate tensile strength were significantly improved to (250.2 +/- 3.5) MPa and (312 +/- 3.7) MPa, respectively, while the elongation was still maintained at a high level of 15.2%. Furthermore, the homogenized microstructure reduced the tendency of localized corrosion and favored the development of uniform passivation film. Thus, the degradation rate of WE43 parts was decreased by an order of magnitude. Besides, in-vitro cell experiments proved their favorable biocompatibility.