Thermal stability of AlCoCrCuFeNi high entropy alloy thin films studied by in-situ XRD analysis

Abstract

High entropy alloys (HEAs), containing five to thirteen metallic elements, with a concentration in the range of 5 to 35 % for each element, exhibit very interesting properties (mechanical, tribological, formability, magnetism...). Their high mixing entropy promotes the formation of simple solid solutions with amorphous or nanocrystallized structure. Bulk pieces of these alloys are known to be stable at relatively high temperature (until 800°C). We study the stability of AlCoCrCuFeNi thin film at temperatures in the range 110 -810 °C. HEA thin films are deposited by magnetron sputtering of mosaic targets. In-situ X-ray diffraction performed during annealing evidences damages of the film above 510°C depending on the initial structure (or chemical composition) of the as-deposited HEA. Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) analysis carried out before and after annealing on both studied samples, show that partial evaporation of the thin film, crystalline phase transformation and chemical reaction with the substrate may take place during annealing.

High-Entropy Alloys: A Critical Review

“…HEA coatings/claddings can also be prepared by sputtering or other cladding techniques. [22,23,73,[133][134][135][136][137][138][139][140] In terms of the phase and crystal structure of HEAs, most of our knowledge is based on the as-cast state (after vacuum arc melting). Very little is known about the equilibrium phases and phase diagrams, but these are key to the design and development of HEAs.…”

Solid-Solution CrCoCuFeNi High-Entropy Alloy Thin Films Synthesized by Sputter Deposition

“…[20][21][22] Due to the unique properties of HEAs, it would be very promising to employ HEAs as a thin-film material. Amongst the reported HEA thin-film work, [23][24][25][26][27] Huang et al [24] reported the sputter deposition of an amorphous phase of an AlCrCoCu 0.5 FeNi film. Dolique et al [25] deposited crystalline films and determined that the microstructure of the film was dependent on the operating power of the sputtering target.…”

High-Entropy Alloys Deposited by Magnetron Sputtering

“…For instance, the presence of copper, which crystallizes into a FCC structure, is found to promote the formation of a FCC solid solution. This is also the case for Co and Ni, whereas, Cr and Fe, crystallizing into BCC structure, induce the formation of a BCC solid solution [1]. However, pure Al having also a FCC structure, leads to the formation of a FCC solid solution if the concentration is below 15 % and a BCC solid solution if the concentration is higher than 15 % [2].…”

“…Their mixing entropy is high, leading to the formation of random solid solutions during solidification, rather than intermetallic compounds. They exhibit very interesting properties: hydrophobicity, good temperature stability [1], high stiffness, strength and toughness, high hardness, corrosion resistance, superplasticity and high-strain-rate superplasticity.…”