Using beam shaping for microstructure tailoring in laser-based powder bed fusion of metals

In laser-based powder bed fusion of metals (PBF-LB/M), ring- and point-ring-shaped beam profiles are increasingly used as an alternative to the common Gaussian beam profile. The changes in the shape of the energy input influence both the process and the resulting component characteristics. The modified energy input alters the temperature distribution and its evolution during processing, which in turn influences the solidification behavior of the material and can consequently modify the as-built microstructure. If it is known how the microstructure changes through the use of different beam profiles, this is a large step towards tailoring microstructures and component properties. Accordingly, load path-dependent topology optimizations would be possible. In our contribution, we first show how different microstructure characteristics (texture, grain size, etc.) change depending on the beam profiles and scanning strategies used to process AISI 316L. Via the relative redistribution of laser power of a point-ring-shaped beam profile from the core to the surrounding ring, it is, for example, possible to rotate the texture from a <100> || BD to a <111> || BD preferred texture. Second, we show that different microstructures can be combined within one component. Due to epitaxial grain growth in PBF-LB/M, the microstructure of the underlying layers strongly influences the formation of the microstructure in the subsequent layers. The transition zones between the two microstructure areas differ depending on the grain size in deeper layers. If the microstructure of deeper layers contains larger grains, the transition zone is disproportionately larger.