Metal Additive Manufacturing Conference - MAMC 2024

Laser powder bed fusion (L-PBF) has become a widely used process in the additive manufacturing of metals, for it combines the assets of a high degree of freedom in the design of parts with a high flexibility in the production process itself. In addition, material properties of L-PBF parts have been demonstrated to be able to equal or, in some cases, even exceed those of comparable, yet conventionally manufactured parts. Here, we address a further aspect inherent to L-PBF: the possibility of producing varied alloys of complex chemical composition based on elemental powders. The primary focus of our investigation is on refractory-based complex concentrated alloys (R-CCAs) within the Ti-Al-Cr-Mo(-Nb) system. Recently, these alloys have been attracting increasing attention because of their promising high-temperature properties. A common production method of bulk R-CCAs is conventional casting, which is, however, according to literature also associated with a strong segregation phenomenon. In this work, the potential of L-PBF is explored with regard to the fabrication of fine-grained, homogeneous bulk material from powder blends. R-CCA specimens were prepared by means of in-situ alloying. According to this approach, an alloy was formed from a pre-mixed blend of elemental powders directly in the powder bed of the 3D printer, and the best possible homogeneity was obtained by making use of the small melt pools and a high localized heat input inherent to the L-PBF method. Different printing parameter sets were tested. Based on X-ray diffraction as well as light-optical and scanning electron microscopy, these parameter sets were further correlated with the microstructural features of the printed parts. In this presentation, the achieved porosity, homogeneity, and prevalent crystallographic phases will be critically discussed.