Glass Forming Ability of Ni-Pd-P Alloys

Abstract

The purpose of the present work is to evaluate the glass forming ability of Ni-Pd-P alloys by measuring the critical cooling rate for glass formation. Measurement of the quenching rate from the melt was made by using a modified piston-anvil type equipment. The cooling rate to obtain a perfectly amorphous phase was determined from the examination of the microstructure of the quenched sample by X-ray analysis and optical microscopy. With an addition of Pd up to 40 at% the critical cooling rate decreased significantly from about 106.6 K·s−1 extrapolated for Ni80P20 alloy to 102.8 K·s−1 for Ni40Pd40P20 alloy. Further addition of Pd increased it to 104.3 K·s−1 for Ni27Pd53P20 alloy. The effect of phosphorous on the critical cooling rate was remarkably large and the minimum value was obtained at 20 at%P. Such composition dependence of the critical cooling rate can be explained in terms of the change in the liquidus temperature and the viscosity of undercooled liquid.