Processing of Thermoelectric Fe2VAl Heusler-compounds by laser powder bed fusion: From single scan tracks to bulk material

Abstract

In the present study, the n-type Fe${}_2$ VAl_0.9 Si_0.1 was printed by laser powder bed fusion (L-PBF) for the first time. This work highlights the complexity of processing non-metallic materials by L-PBF and the need for advanced optimization strategies. A Single Scan Tracks (SSTs) analysis was conducted as usually done for materials newly processed by L-PBF as well as a top-down approach based on printing parameters of stainless steel. Process parameter sets based on SST analysis led to overheating while the stainless-steel-based strategy successfully produced bulk samples. Printed samples transitioned rapidly from cold defects (i.e. lack-of-fusion) to overheating as the printing parameters were varied. Moreover, high density samples were printed with parameters that would produce insufficient melting in the case of SSTs. Successive parallel tracks were printed and revealed a transition from unmelting to balling to continuous densification, demonstrating the critical role of heat accumulation. The microstructure of printed samples was analyzed, and their thermoelectric properties were measured. Transverse cold cracks, perpendicular to the scanning direction were observed. Statistical analysis on SST demonstrated that these cracks were insensitive to laser parameter variations, significantly decreasing the thermoelectric performance of bulk samples.