Phase composition and microstructure of intermetallic alloys obtained using electron-beam additive manufacturing

The paper investigates the microstructure and phase composition of nickel- and aluminum-based intermetallic alloys obtained using two-wire electron-beam additive manufacturing (EBAM). Relevance of the research is related to the widespread use of intermetallic alloys based on nickel and aluminum (mainly Ni 3 Al) in various high-temperature applications and the need to use modern production methods when creating machine parts and mechanisms from these alloys. Using EBAM, the billets from intermetallic alloys with different ratios of the content of main components were obtained. Change in concentrations of the basic elements was carried out varying the ratio of feed rates of nickel and aluminum wires during additive manufacturing in the range from 1:1 to 3:1, respectively. The results of microscopic studies of the obtained alloys showed that, regardless of nickel content, the obtained alloys are characterized by a large–crystalline structure with grain sizes in the range of 100 – 300 μm for alloys with a component ratio of 1:1 and 150 – 400 μm for alloys with a component ratio of 2:1 and 3:1. At the same time, the alloy with an equal content of base components is characterized by more uniform grain and microstructure compared to those with high content of Ni. By changing the concentration ratio of the components, phase composition of the resulting billet can be purposefully controlled. In the case of an “equiatomic” content of the base components in the alloy, a NiAl-based compound with a small phase content based on the intermetallides Ni 3 Al 5 and Ni 3 Al is formed. At high concent­rations of nickel, the intermetallic Ni 3 Al phase is formed, and at a component ratio of 3:1, structure of the resulting billet consists mainly of Ni 3 Al phase and the γ solid substitutional solution based on nickel. The paper demonstrates the possibility of direct production of intermetallic alloys with a given phase composition during electron-beam additive manufacturing.