An important improvement of strength and ductility on a new type of CoCr2.5FeNi2TiW0.5 high entropy alloys under two different protective gases by selective laser melting

High entropy alloys (HEAs) have excellent mechanical properties for wide application range and market demand. However, low ductility is a persistent problem with such alloys. With two different protective gases (Argon and Nitrogen), a new type of high entropy alloy CoCr2.5FeNi2TiW0.5 has been prepared by selective laser melting (SLM) technology for additive manufacturing with discussion and analysis on the influence of microstructure and mechanical properties in this paper. Under the protection of argon (Ar), the HEA forms a single-phase solid solution. Meanwhile, the second phase TiN is formed when nitrogen (N-2) is used as protective gas, which eventually becomes the matrix body-centered cubic (BCC) with precipitates TiN. The average microhardness values of samples under the protection of Ar and N-2 were 436.7HV and 499.2HV, respectively. Along the scanning direction, the SLM sample (N-2 protection) shows higher prop-erties on the average yield strength (YS), ultimate tensile strength (UTS), and average elongation of samples (581 MPa, 893 MPa, and 9.9%, respectively.), compared with those obtained under Ar atmosphere. This method could effectively refine grain structure and offer theoretical guidance to manufacture fine grain materials with high strength and ductility of new HEA components. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A new type of high entropy alloy, CoCr2.5FeNi2TiW0.5, was prepared by selective laser melting technology with two different protective gases, argon and nitrogen. The alloy showed higher microhardness values under nitrogen protection. This method can effectively refine grain structure and provide theoretical guidance for manufacturing fine grain materials with high strength and ductility of new HEA components.