Powder plasma arc additive manufacturing of CoCrFeNiWx high-entropy alloys: Microstructure evolution and mechanical properties

摘要

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 CoCrFeNiWx (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 + mu (x = 0.2 and 0.5), and then to a three-phase combination of FCC + mu + BCC (x = 0.7 and 1.0) with the addition of W. The volume fraction of the mu 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 mu 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.

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