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Spot melting in electron beam powder bed fusion: influence of the melt pool shape on microstructure and texture
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DOI：10.1007/s40964-026-01874-7.png)
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Abstract
En 中文
Reliable microstructure control remains a major challenge in electron beam powder bed fusion, particularly for Ni-based superalloys such as IN718, where large columnar grains with a strong $$\langle 100\rangle $$ texture cause highly anisotropic behavior, often limiting performance under unfavorably aligned or cyclic loads. Current approaches to achieve fine-grained, equiaxed microstructures focus on promoting a columnar-to-equiaxed transition by controlling the local solidification front velocity and the thermal gradient. However, this approach is highly material-specific, requires significant numerical verification and remains difficult to reproduce in complex parts due to the complex required temperature fields. For this purpose, spot melting enables the precise control of local energy input, thereby minimizing cumulative heating and enabling reproducible melt pool formation. In this study, we present a methodology for the experimental quantification of the spot melt pool shape and dimensions and examine how the melt pool geometry and the spatial melt pool arrangement influence the direction of the heat flux at the melt pool boundaries and, consequently, microstructure and texture evolution. By systematically varying the melt pool shape and the spacing between melt spots within a hexagonal lattice, we demonstrate the ability to generate a wide range of microstructures and textures, spanning highly anisotropic columnar microstructures with a $$\langle 100\rangle $$ texture aligned along the build direction, fine-grained isotropic microstructures, and fine-grained, moderately anisotropic microstructures with a $$\langle 111\rangle $$ texture aligned along the build direction, without invoking a columnar-to-equiaxed transition. This offers a promising outlook for complex parts, as it enables to locally choose between equiaxed microstructures and textures tailored to the desired loading direction, thereby further improving the performance of AM components.
Keywords:
Electron beam powder bed fusion
Spot melting
Melt pool shape
Microstructure and texture control
IN718
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