Abstract
The application scope and market demand for additive-manufactured high-entropy alloys (AM HEAs) have broadened of late. However, a long-standing problem associated with AM HEAs is their limited ductility. In this study, a dual-phase AlCoCuFeNi HEA, consisting of body-centered cubic (BCC) solid solution matrix with uniformly dispersed face-centered cubic (FCC) structured precipitates, was fabricated by selective electron beam melting (SEBM). SEBM involved a preheating process can enable the formation of Cu-rich FCC phases with needle-like and spherical morphologies, as well as nanotwins that in-situ precipitated from the metastable BCC(B2) matrix. The compressive strength and ductility of the SEBM HEA were superior to those of the HEAs processed by selective laser melting (SLM) AM technique. Furthermore, using selective electron beam remelting (SEB-RM) during SEBM could result in a higher relative density, finer microstructure, and enhanced compressive properties. Particularly, the SEB-RM sample exhibited a better compressive strength of 2572 MPa, a yield strength of 870 MPa, and a strain of 18.3%. The improved mechanical properties of SEBRM samples could be ascribed to the refined grains and the formation of FCC precipitates, mostly along the grain boundaries. This provides new insights into the dual-phase HEAs-fabricated via a combination of the SEBM additive manufacturing process and selective electron beam remelting-that exhibit in-situ strengthening. (c) 2021 Elsevier B.V. All rights reserved.
NSTL
Elsevier