Surface Re-Melting Strategy Assisted Lpbf In-Situ Alloying Technology

Abstract

The Laser Powder Bed Fusion (LPBF) in-situ alloying technology, utilizing heterogeneous powder blends as raw materials, has revolutionized the freedom of alloy composition design for Additive Manufacturing (AM). However, achieving in-situ metallurgy between heterogeneous powders and ensuring the uniform distribution of alloying elements while maintaining sample formability remains a significant challenge for this technology. The work proposes the process strategy of surface remelting-assisted LPBF in-situ alloying and can be adapted to a wide range of alloying elements. FeCoCrNi alloys with equal atomic ratios were successfully fabricated using self-developed equipment combined with multiple surface remelting processes. Analysis results demonstrate that regional segregation and micro segregation of elements can be significantly improved while ensuring that the sample's density exceeds 99% by incorporating the surface remelting process into LPBF in-situ alloying samples twice. Multiple surface remelting has no noticeable coarsening effect on the grain. The average grain size of the sample with 5 times of surface remelting is only 2.7 μm higher than that of the sample prepared using traditional pre-alloyed powder. The surface remelting strategy can induce a dislocation strengthening effect on the sample. Consequently, an increase in the number of surface remelting cycles enhances both the strength and plasticity.

Keywords: Laser powder bed fusion, In-situ alloying, Remelting strategy, additive manufacturing, Medium entropy alloy, Composition design