Selective laser melting of the Al0.3CoCrFeNiCu high-entropy alloy: Processing parameters, microstructure and mechanical properties

The as-printed Al0.3CoCrFeNiCu high-entropy alloy (HEA) was fabricated from gas-atomized powders by selective laser melting (SLM) with the tailored printing parameters. The processing parameters, microstructural characteristics, mechanical properties and formed defects of the SLM-processed Al0.3CoCrFeNiCu HEA were examined in detail. The SLM-processed HEAs presented a simple disordered face centered cubic solid solution with columnar grains growing along the building direction and exhibiting a 〈0 0 1〉 preferred orientation. Dendritic-segregation, a common phenomenon occurring in as-cast counterparts was eliminated, thus providing a significant method to form a single-phase solid solution. The cellular structure in the columnar grains germinated perpendicular to the boundary of molten pools. In addition, dislocations induced by internal stress were observed. Accordingly, the SLM-processed Al0.3CoCrFeNiCu HEA exhibited superior microhardness and compressive strength. Finally, two types of defects were found in this SLM alloy, including irregular holes and hot cracks. The latter occurring on solid–liquid interface of molten pool were retarded by grain boundaries and then turned into muti-branches. Nevertheless, no crack-free sample could be prepared even though the printing parameters were optimized to achieve a high relative density of 99.08%, indicating this HEA was not suitable for SLM technology to prepare.