The iron aluminide Fe 3 Al has been successfully processed by selective laser melting (SLM) and laser metal deposition (LMD). Process parameters have been determined by which defect free and dense (.99.5%) samples were produced. However, due to the low thermal conductivity of Fe 3 Al, preheating the substrate to 200°C was necessary to prevent cracking during cooling. Microstructural characterization by electron backscatter diffraction (EBSD) showed that in spite of the high cooling rates large elongated grains grew in the building direction, more distinctive for SLM than for LMD. These grains show a continuous change in the crystallographic orientation. Evaluation of the compressive flow stress showed that the anisotropic microstructure results in anisotropic mechanical properties, depending whether the samples are loaded in building direction or perpendicular to it. The alloy shows a very high strength up to 600°C and -concerning the coarse microstructure -becomes ductile already at low temperatures.
By laser metal deposition (LMD) samples from Fe–28Al (at.%) have been built on iron and various steels. Chemically graded iron aluminium and Fe–28Al/steel samples were fabricated with intended concentration gradients by controlling the feed rates of the powders. All samples were subsequently heat treated at 700 °C for 1000 h to study possible reactions between Fe–28Al and the steels and the long-term stability of the composition gradients. Microstructures were characterized by scanning electron microscopy (SEM) and concentration profiles along the building direction were analysed by energy- and wavelength-dispersive spectrometry (EDS, WDS).
A device to grow oxide single crystals via powder based laser additive manufacturing has been built and successfully tested. Single crystals of sapphire as demonstrator materials have been grown to prove the ability of this technique. A sapphire seed disk with a diameter of 25.4 mm is heated in a high temperature furnace up to 1550 °C. Through a hole of the furnace-lid, the seed disk is irradiated by CO2 laser radiation. Simultaneously, Al2O3 powder is fed into the furnace via ceramic tubes. The molten material solidifies on the seed material with exactly the same crystallographic orientation, thus retaining the single crystal structure. A crack free single crystal of a few millimeters in height is produced
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.