Effect of Er and Zr additions and aging treatment on grain refinement of aluminum alloy fabricated by laser powder bed fusion

In this work, Al-0.88Er-0.78Zr (wt%) alloy was fabricated via laser powder bed fusion (LPBF). The microstructure, precipitates distribution, electrical conductivity and hardness of as-built and aging treatment specimens were carefully characterized. Results show that LPBF process greatly expand the solid solubility of Er and Zr in Al. The addition of Er can significantly refine the grain size and form a bimodal grain structure consisting of fine equiaxed grains (grain size similar to 0.53 +/- 0.15 mu m) at the boundary of molten pool together with coarse columnar grains (width 2.57 +/- 0.84 mu m) at the center of molten pool. After 375 celcius for 3 h aging treatment, the particles on the grain boundary inhibit the grain growth; at the same time, a large number of Al3(Er,Zr) particles with L12 structure and size of 2.25 +/- 0.3 nm are precipitated, which plays a major role in enhancing the hardness with the peak hardness of about 89.24 +/- 3.77 HV. Er and Zr elements are proved to be an alternative way of the additive elements for developing a new 3D printing high-strength aluminum alloy.(c) 2022 Elsevier B.V. All rights reserved.