Transformations in CrFeCoNiCu High Entropy Alloy Thin Films during In-Situ Annealing in TEM

Abstract

In-situ TEM-heating study of the microstructural evolution of CrFeCoNiCu high entropy alloy (HEA) thin films was carried out and morphological and phase changes were recorded. Post annealing investigation of the samples was carried out by high resolution electron microscopy and EDS measurements. The film is structurally and morphologically stable single phase FCC HEA up to 400 °C. At 450 °C the formation of a BCC phase was observed, however, the morphology of the film remained unchanged. This type of transformation is attributed to diffusionless processes (martensitic or massive). From 550 °C fast morphological and structural changes occur, controlled by volume diffusion processes. Fast growing of a new intermetallic phase is observed which contains mainly Cr and has large unit cell due to chemical ordering of components in <100> direction. The surface of the films gets covered with a CrO-type layer, possibly contributing to corrosion resistance of these.

Fast mechanical synthesis, structure evolution, and thermal stability of nanostructured CoCrFeNiCu high entropy alloy

“…Among HEAs, CoCrFeNiCu composition has been extensively studied earlier as HEA thin films and coatings deposited by magnetron sputtering [27,28], as volume HEA materials (mechanically alloyed powders and consolidated bulk samples) [29][30][31][32][33]. Different amounts of Ti and Al are usually added to study the phase evolution, mechanical and magnetic properties of designed systems [16,17].…”

“…Their structure differed from that of as-cast bulk CoCrFeNiCu alloy used as a target; it was composed of two fcc phases, Cu-rich and Cu-depleted ones. Arfaoui et al [28] studied the sputtered single-phase fcc CoCrFeNiCu in thin films by in-situ TEM annealing. The structural and morphological stability of single-phase fcc HEA thin film was found stable up to 400°C.…”

“…Starting from 450 °C a bcc phase without any changes in morphology was observed. This type of transformation was referred to as the diffusionless process [28]. Further increase in temperature leads to structural and morphological changes controlled by volume diffusion processes.…”

Thermal Stability of Medium- and High-Entropy Alloys of 3d-Transition Metals

“…An et al have found that thin films were composed of FCC grains with preferential (111) orientation as compared to as-cast Cu-CoCrFeNi HEAs where two FCC phases were detected (3.58 Å and 3.61 Å): a Cu-rich phase in interdendritic regions and a Cu-poor phase in dendritic morphology 37 . The in-situ annealing in TEM of Cu-CoCrFeNi thin films prepared by magnetron sputtering has been evaluated in 38 in the temperature range [673 K-973 K] for 5 min. Up to 673 K, a single FCC phase was observed.…”

Effects of Annealing on the Microstructure and Wear Resistance of Laser Cladding CrFeMoNbTiW High-Entropy Alloy Coating

“…Annealing an HEA coating deposited by laser cladding has important impacts on its microstructure and wear resistance [17][18][19][20][21][22][23]. Ye et al [17] fabricated an Al x FeCoNiCuCr HEA coating on an AISI 1045 steel substrate by means of laser cladding.…”