Laser additive manufacturing high-throughput synthesis of NbMoTaW series high-entropy alloy

In 2011, U.S. Air Force Laboratory Senkov [1] The NbMoTaW ultra-high temperature and high-entropy alloy system is proposed. The equimolar NbMoTaW ultra-high-temperature and high-entropy alloy exhibits excellent mechanical properties at high temperatures. Its yield strength and compressive strength at 1600°C reach 405MPa and 600MPa, respectively, which are better than the current ones. Commonly used INCONEL 718 and HAYNES 230 high-temperature alloys. Since then, ultra-high temperature and high entropy alloys have gradually become a research hotspot in the industry. However, the research on the composition ratio of high-entropy alloys has always belonged to a relatively unexplored field of quasi-infinite space. Whether the equimolar ratio is the optimal composition of high-entropy alloys has always been controversial.

Moorehead [2] The high-throughput screening technology is coupled with the laser additive manufacturing technology, and the reorganization design of the NbMoTaW high-entropy alloy composition is realized by adjusting the powder feeding rate of the four-way powder barrel separately, and then the material is formed and prepared by the laser additive manufacturing technology. The whole process is shown in Figure 1. Due to the differences in the geometry, reflectivity, vapor pressure and other physical variables of each powder element, these factors will have an impact on the absorption of laser energy. Therefore, there are often differences between the ideal alloy design composition and the final alloy composition. In the research, through multiple printing and prediction refinement, the gap between the predicted component and the measured component was successfully narrowed. The NbMoTaW high-entropy alloy group formed by laser additive manufacturing has a similar microstructure, compared with the NbMoTaW high-entropy alloy formed by vacuum arc melting. Due to the rapid solidification, its substructure is significantly refined and the degree of microsegregation is smaller, as shown in Figure 2. Through X-ray diffraction (XRD), 31 groups of NbMoTaW high-entropy alloys with different compositions were tested. All the tested alloys only have a simple disordered BCC body-centered cubic structure, as shown in Figure 3.

In this study, the high-throughput synthesized NbMoTaW series high-entropy alloy was successfully formed and prepared by laser additive manufacturing technology. By using elemental element powder, all elements in the high-entropy alloy can be combined in any linear manner, which is the future high-throughput The design and preparation of high-entropy alloys laid the foundation.

references:

ON Senkov, GB Wilks, JM Scott, et al. Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys[J]. Intermetallics, 2011, 19: 698-706.

Michael Moorehead, Kaila Bertsch, Michael Niezgoda, et al. High-throughput synthesis of Mo-Nb-Ta-W high-entropy alloys via additive manufacturing[J]. Materials and Design, 2020, 187: 108358.

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