Effects of laser scanning rotation angle on microstructure and mechanical properties of selective laser melted FeCoCrNiMn-(N, Si) high entropy alloy

In this paper, FeCoCrNiMn-(N, Si) high-entropy alloy was fabricated by selective laser melting process, at laser scanning rotation angles of 45°, 67° and 90°. The hierarchical microstructure, grain size and morphology, hot cracks and mechanical properties of the three specimens were systematically investigated using various characterization techniques. The results show that the sample prepared at laser scanning rotation angle of 45° mainly shows columnar dendrites grown epitaxially across the melt pool with large grain size (about 128 μm), as well as a high density of hot cracks. In contrast, the sample prepared at laser scanning rotation angle of 67° has a high density of cellular structure, a high density of dislocation entanglements existing both along the cell walls and inside the cells, a fine grain size of about 69 μm and a low density of hot cracks. The hierarchical microstructure prepared by selective laser melting can effectively improve the mechanical properties. The deformation mechanism of FeCoCrNiMn-(N, Si) high-entropy alloys is as follows: a small number of the deformed microbands at low strain, high-density deformation microbands and a small number of nanotwins at the high strain. © 2023 Central South University of Technology. All rights reserved.