Evolution of Structure in AlCoCrFeNi High-Entropy Alloy Irradiated by a Pulsed Electron Beam

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.

Deformation Behavior of 3D‐Printed High‐Entropy Alloys: A Critical Review

“…[ 75,76 ] In comparison with other AM processes, the use of WAAM for HEA fabrication is very recent and emergent. [ 27 ] Since 2021, HEAs built using WAAM include Fe 50 Mn 30 Cr 10 Ni 10 , [ 77 ] AlCrFeCoNi, [ 78–80 ] Al 2.1 Co 0.3 Cr 0.5 FeNi 2.1 , [ 81 ] CrMnFeCoNi, [ 82 ] and Co 25.4 Cr 15 Fe 37.9 Mn 3.5 Ni 16.8 Si 1.4 . [ 83 ] To prepare HEAs via WAAM, wires of multiple materials can be combined, [ 79–81 ] e.g., by twisting, [ 78 ] stranding, [ 82,83 ] and subsequently used as a feed for 3D‐printing.…”

“…[ 27 ] Since 2021, HEAs built using WAAM include Fe 50 Mn 30 Cr 10 Ni 10 , [ 77 ] AlCrFeCoNi, [ 78–80 ] Al 2.1 Co 0.3 Cr 0.5 FeNi 2.1 , [ 81 ] CrMnFeCoNi, [ 82 ] and Co 25.4 Cr 15 Fe 37.9 Mn 3.5 Ni 16.8 Si 1.4 . [ 83 ] To prepare HEAs via WAAM, wires of multiple materials can be combined, [ 79–81 ] e.g., by twisting, [ 78 ] stranding, [ 82,83 ] and subsequently used as a feed for 3D‐printing. The WAAM‐fabricated CrMnFeCoNi HEA exhibited an ultimate tensile strength of 499 ± 74 MPa, being lower than that of its SLM and LMD counterparts.…”

Modeling the mechanism of micro / nanostructured surface formation in Al-Co-Cr-Fe-Ni and Co-Cr-Fe-Mn-Ni high-entropy alloys treated with a high current pulsed electron beam

“…Al-Co-Cr-Fe-Ni and Co-Cr-Fe-Mn-Ni HEAs were fabricated by wire-arc additive manufacturing using cabletype welding wires as feeding materials and Ar as a shielding gas (99.99 % purity) [13]. Al-Co-Cr-Fe-Ni welding wire with a diameter of 1.2 mm was composed of Al wire (Al, 99.9 at.%, ∅0.5 mm), Cr-Ni wire (Cr, 20 at.%, Ni, 80 at.%, ∅0.4 mm), and Co-Fe-Ni wire (Co, 17 at.%, Fe, 54 at.%, Ni, 29 at.%, ∅0.4 mm).…”

“…The methods of surface modification also play an important role in the design of HEAs since they allow eliminating some defects as pores or microcracks and increasing durability. For example, the HEA surface can be modified by plasma nitriding [7], laser remelting [8], boronizing [9], gaseous carburization [10], ultrasonic nanocrystal surface modification [11] and high current pulsed electron beam treatment (HCPEB) [12,13]. The latter method introduces high energies into the surface layers and forms a cellular microstructure with a grain size of 100 -500 nm, leading to better mechanical and tribological characteristics.…”

“…We assumed that the reason for the formation of a cellular structure is a combination of thermal, evaporationcapillary, and thermoelectric instabilities, since they become important at temperature gradients of 10 6 K / m and molten layer thicknesses of ~1-100 μm [6,7]. According to the results of [12,13], with an increase in the number of pulses or the energy density of the electron beam (E s ), the size of the crystallization cells increases. From the hydrodynamic point of view [14], this can be explained by the fact that with increasing E s values, the losses of the power density of the absorbed electron beam for evaporation increase.…”