Effect of copper addition on the glass forming ability in Pd-Si binary amorphous alloying system

Abstract

The effect of copper addition on the glass forming ability in Pd-Si amorphous alloys was systematically studied by X-ray diffraction and differential scanning calorimeter with a binary alloy series of Pd81+xSi19-x (x=0, 1, 1.5, 2, 2.5, 3, 4) and a ternary alloy series of Pd83.5-xCuxSi16.5 (x=0, 2, 4, 6, 8, 10, 12). It has been found that the critical size of the Pd-Si alloys could be improved significantly from 8mm to 15mm and ΔTx could be enhanced from 18.7 K to 54.7 K with the addition of copper. The determined activation energy demonstrates that Cu additions improve the thermal stability of the system significantly. The different results of the measured criteria to evaluate the GFA for the Pd-Si and the Pd-Cu-Si alloys may be linked to a different crystallization behavior. The enhanced GFA is linked to a more thermodynamically stable liquid and a reduction of atomic diffusion in the ternary alloy by Cu addition.

Metallic Glass Films with Nanostructured Periodic Density Fluctuations Supported on Si/SiO2as an Efficient Hydrogen Sorber

“…1 Fully amorphous Pd82Si18 composition with a deep eutectic can be cast up to 8 mm which is even larger than many other ternary alloys and can be extended to 15 mm with the replacement of small amounts of Pd with Cu. 2 In terms of hydrogen interactions, compared to lattice expansion of the Pd polycrystal nanofilms of the same thickness (50 nm), the calculated maximum H⁄M=1.56 for Pd79Si16Cu5 MG thin film is around 2.5 times larger. 3 Here, the third element Cu disturbs the symmetry of the PdSi-MGs leading to the formation of new interstitial positions for enhanced hydrogen sorption.…”

Interpretation of the apparent activation energy of glass transition

“…( 5) with a magnification factor An interesting point regarding metallic glasses is that viscosity below T g is sometimes measured because of the practical interest in the creep phenomenon. Taub and Spaepen found that the activation energy Q * a of viscosity of Pd 82 Si 18 is almost constant at about 2.0 eV in a temperature range from 420 to 540 K [86]; Pd 82 Si 18 is a metallic glass with T g = 634 K [87]. Interestingly, the value Q * a does not change by annealing at various temperatures.…”