Combinatorial exploration of color in gold-based alloys

Abstract

Combinatorial approaches comprised of combinatorial magnetron co-sputtering deposition and fast screening methods are introduced to study color as a function of composition in Au-based alloys. The microstructures of the thin films and bulk alloys are identified by X-ray diffraction, and their colors of the alloys are characterized by optical reflectivity. The results reveal that when comparing microstructures and reflectivity, thin films are similar to bulk alloys. In AuAg-Cu solid solutions, the color of the ternary alloy follows the rule of mixture. For colors resulting from AuAl 2 intermetallic, the color of an alloy scales with the percentage of the intermetallic phase and the deviation from its ideal binary composition. In the Au-Al-Cu library, we found a ∼90 % AuAl 2 area fraction compositional window where copper addition can be tuned to improve mechanical properties while keeping purple color, even though Al and CuAl 2 phases exist. Moreover, when comparing the color in Au-Cu-Si-Ag amorphous and crystalline state solid solution for the same composition, the colors are essentially identical.

Combinatorial development of antibacterial Zr-Cu-Al-Ag thin film metallic glasses

“…Therefore, a broad composition range is expected to form glass phase under the high cooling rate during sputtering-deposition32. We recently reported that automated X-ray diffraction (XRD) is capable of maping out the atomic structure of the materials library324. Figure 2(b) shows the XRD spectrum for one of the alloys in the materials library.…”

“…In order to develop metallic glasses with optimized antibacterial properties, which can be paired with other required properties, novel development strategies are required. Recent investigations indicate that combinatorial approaches are promising in accelerating development of new metallic glasses324252627. Although the combinatorial approach has been used for the development of antibacterial agents in different materials classes282930, its application in metallic alloys remains limited31.…”

Determination of critical cooling rates in metallic glass forming alloy libraries through laser spike annealing

“…The black region represents considered compositions that crystallized, even upon sputtering. The symbols indicate the composition with the highest measured GFA, reported ternary MG compositions with high GFA 21 , 31 and dotted lines indicating a range, reported binary MG compositions 36 , 37 , the global eutectic composition 34 , and the composition with the lowest nucleation temperature 12 . The compositions in all the Gibbs triangles ( a–e ) are in at.%.…”

“…2g ). T L is extracted from the ternary phase diagram 34 . As the final result, R C is plotted as a function of composition (Figs 3e and 4a ).…”

“…( c ) T rg = T g / T L where T g was estimated 41 by first calculating the elastic moduli 42 , 43 and calibrating with a known T g that was determined by calorimetry 31 (calculation details discussed in caption of Supplementary Fig. 1 ), while T L was extracted from the ternary liquidus projection 34 . ( d ) Applying an efficient cluster-packing structural model for metallic glasses 45 , 100% efficiently packed lines for various < Z Si,tot , Z Cu,tot , Z Au,tot > structures were calculated for the composition region of interest.…”