Design and Development of High-Entropy Alloys with a Tailored Composition and Phase Structure Based on Thermodynamic Parameters and Film Thickness Using a Novel Combinatorial Target

Abstract

This study presents a novel synthesis route for high-entropy alloys (HEAs) and high-entropy metallic glass (HEMG) using radio frequency (RF) magnetron sputtering and controlling the HEA phase selection according to atomic size difference (δ) and film thickness. The preparation of HEAs using sputtering requires either multitargets or the preparation of a target containing at least five distinct elements. In developing HEA-preparation techniques, the emergence of a novel sputtering target system is promising to prepare a wide range of HEAs. A new HEA-preparation technique is developed to avoid multitargets and configure the target elements with the required components in a single target system. Because of a customizable target facility, initially, a TiZrNbMoTaCr target emerged with an amorphous phase owing to a high δ value of 7.6, which was followed by a solid solution (SS) by lowering the δ value to 5 (≤6.6). Thus, this system was tested for the first time to prepare TiZrNbMoTa HEA and TiZrNbMoTa HEMG via RF magnetron sputtering. Both films were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, field emission scanning electron microscopy cross-sectional thickness, and atomic force microscopy (AFM). Furthermore, HEMG showed higher hardness 10.3 (±0.17) GPa, modulus 186 (±7) GPa, elastic deformation (0.055) and plastic deformation (0.032 GPa), smooth surface, lower corrosion current density (I corr), and robust cell viability compared to CP-Ti and HEA. XRD analysis of the film showed SS with a body-centered cubic (BCC) structure with (110) as the preferred orientation. The valence electron concentration [VEC = 4.8 (<6.87)] also confirmed the BCC structure. Furthermore, the morphology of the thin film was analyzed through AFM, revealing a smooth surface for HEMG. Inclusively, the concept of configurational entropy (ΔS mix) is applied and the crystalline phase is achieved at room temperature, optimizing the processing by avoiding further furnace usage.

Synthesis of High-Entropy Alloys with a Tailored Composition and Phase Structure Using a Single Configurable Target

“…The patterns confirmed the amorphous structure of the thin films grown under WHT conditions and a minor crystalline structure of the annealed thin films. These results demonstrated that a more crystalline structure could be synthesized using the proposed target configuration based on a combination of refractory elements, as previously reported. , The diffraction data and calculated VECs are summarized in Table , indicating that the prepared thin films exhibited dual-phase FCC and BCC as well as single FCC structures. The planes (111), (222), and (200) corresponded to the FCC structure, whereas (200), (211), (310), (222), and (330) were attributable to the BCC structure.…”

“…This process involved the simultaneous arrangement of 20 pieces, as shown in Figure a, which were then combined into a single target configuration using a ceramic screw. This innovative approach led to the development of a novel target system, enabling the customization of alloy compositions to meet the specific requirements of various applications requiring HEAs, as demonstrated previously . Furthermore, the precise positioning of each constituent element and the total number of elements played key roles in ensuring a consistent alloy composition.…”

“…Furthermore, the elemental ratios can be tuned and elements can be replaced as needed. This technique has been previously used to efficiently prepare a wide range of highly crystalline refractory HEAs, such as TiZrNbMoTa and TiMoVWCr. , Furthermore, the phase structure, including face-centered cubic (FCC) and mixed FCC and body-centered cubic (BCC) phases, can be controlled by adjusting the valence electron concentration (VEC). Mixed FCC + BCC structures can be synthesized by using target elements in a 1:1 ratio (Co 20 Cr 20 Mo 20 Mn 20 Ni 20 (target 1)).…”