Influence of Processing Variables on the Morphology and Microstructure of a Non-Stoichiometric Complex Concentrated Alloy
The development of high-entropy alloys has been a major area of research in recent years.The compositionally complex alloy Al_1_0Co_2_5Cr_8Fe_1_5Ni_3_6Ti_6 has been promoted as an optimizedchemistry exhibiting medium hardness with good ductility and high tensile strength. This thesisaims to provide insight into the growth of Al_1_0Co_2_5Cr_8Fe_1_5Ni_3_6Ti_6 as a surface coating and into theinfluence of coating morphology on its interdiffusion behavior. Coatings were deposited via highrate unbalanced direct current magnetron sputtering. Deposition conditions were selected tosurvey processing-property relations relative to the structure zone model for thick film growthproposed by Thornton. Thick micro-scale coatings were deposited onto CMSX-8 Ni-based superalloy substrates at various temperatures and Ar gas pressures and later annealed to observe diffusion behavior. Coating morphology, chemical analysis, and crystallographic identification were performed using scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction. Coatings produced at 5 mTorr Ar pressure displayed dense Zone T or mixed Zone T + Zone 2 morphologies and the least amount of diffusion into the substrate upon annealing. Some of the samples at high pressures and temperatures possessed porous, fibrous Zone 2 morphologies caused by a high incident angle between the substrate and sputter gun.