Improve the Microstructure and Properties of Al0.5cocrfeni High Entropy Alloy Fabricated by Selective Laser Melting with Electropulsing Treatment

Abstract

In order to improve the microstructure of the Al0.5CoCrFeNi high entropy alloy (HEA) prepared by selective laser melting (SLM), the electropulsing treatment (EPT) has been used on it as a post processing in this study. The strengthening and softening mechanism was analyzed by comparing the microstructure of SLM-Al0.5CoCrFeNi HEA under different EPT parameters. At a 10 seconds power on time, the substructure size of HEA decreases continuously with increasing voltage. Under 90V10s EPT, the yield strength increased from 658 MPa in the printed state to 748 MPa, and the microhardness increased from 265 HV0.1 to 305 HV0.1. At a voltage of 90 V for 20 seconds, the cellular substructure disappears, and a large number of uniformly distributed BCC phases precipitates inside the FCC matrix. At 90V30s EPT, recrystallization occurs and the BCC phase coarsen. Dislocation network is the main factor affecting the strength of SLM-HEA. EPT can change the dislocation network structure to enhance the strength of SLM-HEA. Simultaneously, the EPT effectively promotes the transition from FCC phase to BCC phase in a short time. Joule heat and electronic wind force are the main reasons for the change of structure and properties of SLM-Al0.5CoCrFeNi HEA. This work provides a post-processing method of using EPT technology to effectively control the crystal structure in additive manufacturing HEA products.

Keywords: Electropulsing treatment, Selective laser melting, high entropy alloy, Recrystallization, mechanical properties