Cycling Effect on Undercooling in Pd_(40)Cu_(30)Ni_(10)P_(20) Melt

摘要

The influence of large number of heating and cooling cycles on the nucleation and hence on the undercooling of Pd_(40)Cu_(30)Ni_(10)P_(20) melt has been investigated by differential scanning calorimety. The repeated undercooling measurements allow the investigation of the stochastic nature of the nucleation process. It is found that the value of the undercooling monotonically decreases with increasing cycle number up to about 100 cycles. The melting temperature of the alloy on the other hand remains constant up to 60 cycles and then it increases by 85°C. Structure characterisation by X-ray diffraction and scanning electron microscopy measurements reveals that a Cu-O oxide layer is gradually formed with increasing cycle number. This causes a depletion of copper in the interior of the sample and therefore decreases the glass forming ability of the alloy. A correlation of cycling dependence of melting, liquidus, and nucleation temperatures with the microstructure evolution is presented.