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Powder plasma arc additive manufacturing (PPA-AM) is a promising method for the preparation of high-entropy alloys (HEAs), and has the advantages of low cost, high efficiency, and high quality. In this study, the CoCrFeNiW x (x = 0, 0.2, 0.5, 0.7, and 1.0) HEAs were successfully prepared via the PPA-AM technique. Microstructure and mechanical properties of alloys with different W content were investigated. The results showed that the microstructure changed from a single FCC phase (x = 0) to the dual-phase FCC + µ (x = 0.2 and 0.5), and then to a three-phase combination of FCC + µ + BCC (x = 0.7 and 1.0) with the addition of W. The volume fraction of the µ phase and BCC phase increases with the increase in W content, while the size of FCC columnar grain is significantly reduced. The solid-solution strengthening of the FCC phase and the second phase strengthening were mainly responsible for the increase in the microhardness (136–413 HV) and yield strength (187–567 MPa) while the brittleness of the μ phase contributes to the expansion of the crack, which leads to a decrease in the ductility (50.8% to 0.3%). These results can provide a systematic understanding of the phase transformation of PPA-AM HEAs with different W content and its effects on the mechanical properties. • Powder plasma arc additive manufacturing (PPA-AM) of CoCrFeNiWx high-entropy alloys. • PPA-AM can produce high-entropy alloys with lower cost and high efficiency. • The microstructure and mechanical properties of the CoCrFeNiWx HEAs were investigated. • W element can promote the phase transformation from FCC phase to µ and BCC phase. • The strength of the HEAs was significantly improved with addition of W. [ABSTRACT FROM AUTHOR]

• AlCoCrFeNi 2.1 high-entropy alloy was fabricated by PPA-AM method. • The B2 phase precipitates at the bottom region of the HEA due to thermal cycling. • The ductility of the HEA increases and the strength decreases due to thermal cycling. High-entropy alloys (HEAs) are a novel class of materials. In this study, the AlCoCrFeNi 2.1 HEA was prepared using powder plasma arc additive manufacturing (PPA-AM). The influence of thermal cycling in the PPA-AM process on AlCoCrFeNi 2.1 HEA was investigated. The AlNi elements in the FCC phase in the bottom region were aggregated by thermal cycling to form the acicular B2 particles. This weakened the solid solution strengthening effect of the FCC phase, reduced its yield strength (421 to 389 MPa), and improved its ultimate tensile strength (929 to 981 MPa) and elongation (15.6 % to 21.0 %). The results of this study might have reference significance for the AlCoCrFeNi alloy system. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) are promising coating materials for wear resistance applications. However, the preparation of HEA coatings with powder has the disadvantages of high cost and low efficiency. In this study, an innovative triple-wire plasma arc cladding (TW-PAC) method was used to prepare HEA coatings. Nonequiatomic Cr-Fe-Ni-Ti x (x is Ti wire feeding speed, x = 0, 0.5, 0.8 and 1.0 m/min, denoted as Ti 0 , Ti 0.5 , Ti 0.8 and Ti 1.0) HEA coatings were successfully prepared by using three commercial wires (ERTi-2, ER304L and Cr 20 Ni 80 wire). With increasing Ti content, the structure of the Cr-Fe-Ni-Ti x HEA coatings changed from the single FCC phase to the FCC + γ′ (Ni 3 Ti) + Laves (Fe 2 Ti) phase, and the microhardness of the coatings increased from 137 HV to 873 HV. Due to the addition of Ti, Ni 3 Ti and Fe 2 Ti phases with high hardness precipitated in the alloy coating, accompanied by the solid solution strengthening effect of the FCC phase, the wear resistance of the coatings was significantly improved (from 9.67 × 10−4 to 1.49 × 10−4 mm3/N·m). The results of this study contribute to the preparation of thick HEA coatings overlarge areas at low cost and with high efficiency and provide new insights into Cr-Fe-Ni-Ti x HEA coatings. • Triple-wire plasma arc cladding (TW-PAC) of Cr-Fe-Ni-Tix high-entropy alloy coatings. • High-entropy alloy coatings were prepared using three commercial wires. • The phase of the coatings changed from FCC to FCC + Ni 3 Ti + Fe 2 Ti with the addition of Ti. • The wear resistance of the coatings was significantly improved with addition of Ti. [ABSTRACT FROM AUTHOR]