Effects of elemental segregation and scanning strategy on the mechanical properties and hot cracking of a selective laser melted FeCoCrNiMn-(N,Si) high entropy alloy

Abstract The effects of scanning rotation, elements N and Si additions on the grain size distribution, elemental segregations, mechanical properties and hot cracking behaviors of a FeCoCrNiMn high entropy alloy fabricated by selective laser melting were systematically investigated. The alloy fabricated by 45° scanning rotation strategy has a higher hot crack density than by 67° scanning rotation strategy, due to the prevailing epitaxial growth of the columnar dendrites and withstanding high local strain and low strength. The additions of N and Si elements promote the preferred segregations of Mn and Ni elements, which facilitates the initiation and propagation of the intergranular hot cracks. The investigation also illustrates that the additions of N and Si elements can form a hierarchical structure, including elemental segregations, dislocation cell, nanotwins, fine precipitates and multimodal grain structure, which effectively improve the mechanical properties. The investigation indicates that in order to prepare a crack-free alloy, the processing parameters and alloy composition should be carefully tailored to reduce the epitaxial growth of dendrites, and to avoid the elemental segregation.