Abstract
High-current pulsed electron-beam (HCPEB) surface modification of Al-Co-Cr-Fe-Ni high-entropy alloy (wt. %) Al—15.64; Co—7.78; Cr—8.87; Fe—22.31; Ni—44.57, fabricated via wire-arc additive manufacturing was studied. The initial condition of the sample is characterized by a highly inhomogeneous distribution of the chemical elements that form the alloy. The alloy samples were irradiated with the different electron beam energy densities of 10, 20 and 30 J/cm2. The surface structure was then analyzed in relation to an energy deposition mode. The study has established that HCPEB induces a high-speed crystallization structure with cells varying in size from 100 to 200 nm. There are nano-dimensional (15–30 nm) second-phase inclusions enriched with atoms of Cr and Fe along the grain boundaries. The most liquating elements are Cr and Al. Electron beam surface modification of the high-entropy alloy induces its homogenization. The study has highlighted that the mode of 20 J/cm2, 50 µs, 3 pulses, 0.3 s−1 results in the formation of a surface layer with the most homogenously distributed chemical elements.
Highlights
In the early 21st century, scientists began developing and thoroughly examining socalled high-entropy alloys (HEAs) consisting of at least five principal elements in equal or close to equal atomic ratios [1,2]
The previous studies have shown that HEAs mostly form simple face center cubic (FCC), body center cubic (BCC), or FCC + BCC solid solution structures instead of lots of intermetallics, which can be explained by the solid solution formation rules proposed by Zhang et al [3,4]
Since High-current pulsed electron-beam (HCPEB) is proven to be a promising method of surface modification of HEAs and only a limited number of studies have focused on using this technology, this research aimed to study the evolution of the structure in Al-Co-Cr-Fe-Ni high-entropy alloy fabricated by wire-arc additive manufacturing and modified by a high-current pulsed electron beam with different electron beam densities
Summary
In the early 21st century, scientists began developing and thoroughly examining socalled high-entropy alloys (HEAs) consisting of at least five principal elements in equal or close to equal atomic ratios [1,2]. There are four core effects of HEAs that are usually used to describe the concept of these alloys: the high entropy effect, the lattice distortion effect, sluggish diffusion, and the “cocktail” effect [5,6]. The results obtained in previous studies showed that Al-Co-Cr-Fe-Ni fabricated by wire-arc additive manufacturing has a high hardness but a relatively brittle structure [16,19]. Some defects such as pores, roughness, and microstructure inhomogeneity are induced in HEA during the manufacturing process. Surface modification has been recognized as an effective way to radically optimize the microstructure and significantly improve the overall performance of the surface [20]
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