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Is the energy density a reliable parameter for materials synthesis by selective laser melting?
2017-3-9, Prashanth, K.G., Scudino, S., Maity, T., Das, J., Eckert, J.
The effective fabrication of materials using selective laser melting depends on the process parameters. Here, we analyse the suitability of the energy density to represent the energy transferred to the powder bed, which is effectively used to melt the particles and to produce the bulk specimens. By properly varying laser power and speed in order to process the powder at constant energy density, we show that the equation currently used to calculate the energy density gives only an approximate estimation and that hatch parameters and material properties should be considered to correctly evaluate the energy density.
Optimizing mechanical properties of Fe26.7Co26.7Ni26.7Si8.9B11 high entropy alloy by inducing hypoeutectic to quasi-duplex microstructural transition
2019, Zhang, Z.-Q., Song, K.-K., Guo, S., Xue, Q.-S., Xing, H., Cao, C.-D., Dai, F.-P., Völker, B., Hohenwarter, A., Maity, T., Chawake, N., Kim, J.-T., Wang, L., Kaban, I., Eckert, J.
High-entropy alloys (HEAs) have inspired considerable interest due to their attractive physical and mechanical properties. In this work, the microstructural evolution induced by different heat treatments on rapidly solidified hypoeutectic precursors of a Fe26.7Co26.7Ni26.7Si8.9B11 HEA is investigated and correlated with the corresponding mechanical properties. The microstructures of the rapidly solidified precursors are composed of primary fcc solid solution dendrites embedded in a eutectic matrix. When the samples are annealed at different temperatures after furnace cooling or quenching, respectively, the eutectic structure gradually decomposes into fcc, tetragonal (Fe,Co)2B, and hexagonal Ni31Si12 crystals with increasing annealing temperature, leading to a gradual increase of the content of the fcc crystals and both their aggregation and coarsening. Then the dominant structural framework gradually transforms from eutectic structures to fcc dendrites and ultimately the (Fe,Co)2B crystals become isolated as dominant reinforcement particles distributed in the interdendritic regions. This gradual microstructural transition from hypoeutectic to quasi-duplex structures leads to the change of the dominant deformation mechanism from crack-controlled to dislocation-dominated deformation, which allows to control both ductility and strength in a wide range. Hence, this study provides some guideline for how to tune the microstructure and mechanical properties of HEAs.