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Surface segregation is a phenomenon common to all multicomponent materials and one that plays a critical role in determining their surface properties. Comprehensive studies of surface segregation versus bulk composition in ternary alloys have been prohibitive because of the need to study many different compositions. In this work, high-throughput low-energy He+ ionscattering spectra and energy-dispersive X-ray spectra were collected from a CuxAuyPd1−x−y composition spread alloy film under ultrahigh vacuum conditions. These have been used to quantify surface segregation across the entire CuxAuyPd1−x−y composition space (x = 0 → 1 and y = 0 → 1 − x). Surface compositions at 164 different bulk compositions were measured at 500 and 600 K. At both temperatures, Au shows the greatest tendency for segregation to the top-most surface while Pd is always depleted from the surface. Higher temperatures enhance the Au segregation. Segregation at most of the binary alloy bulk compositions matches with observations previously reported in the literature. However, surface compositions in the CuPd B2 composition region reveal segregation profiles that are nonmonotonic in bulk alloy composition. These were not observable in prior studies because of their limited resolution of composition space. An extended Langmuir−MacLean model, which describes ternary alloy segregation, has been used to analyze experimental data from the ternary alloys and to estimate pair-wise segregation free energies and segregation equilibrium constants. The ability to study surface segregation across the ternary alloy composition space with high-throughput methods has been validated, and the impact of bulk alloy phase on surface segregation is demonstrated and discussed.
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Study of growth twins and phase formation in CuNiAl alloys via a combinatorial approach
Abstract In this study, a combinatorial and high-throughput approach was leveraged to investigate nanotwin behavior in the ternary CuNiAl alloy system. Combinatorial co-sputtering was used to synthesize 169 unique CuNiAl alloy compositions, which were characterized in both the as-sputtered and annealed conditions to elucidate relationships between composition, nanotwin formation, and phase evolution. Compositional effects on phase formation were investigated using high-throughput X-ray diffraction, while scanning transmission electron microscopy was used to identify nanotwin compositional boundaries and isolate the roles of varied composition and nanotwin formation on microstructural evolution. It was determined that Al content was the primary variable influencing thermal evolution in the nanotwinned CuNiAl alloys, as it altered the thermodynamic driving forces by changing composition and reducing the as-sputtered twin boundary spacing. Overall, this work demonstrates a novel approach to globally study unexplored nanotwin synthesis domains beyond binary alloys. Graphical Abstract
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- PAR ID:
- 10556188
- Publisher / Repository:
- Cambridge University Press (CUP)
- Date Published:
- Journal Name:
- Journal of Materials Research
- Volume:
- 40
- Issue:
- 2
- ISSN:
- 0884-2914
- Format(s):
- Medium: X Size: p. 202-212
- Size(s):
- p. 202-212
- Sponsoring Org:
- National Science Foundation
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