Crystallization And Containerless Solidification Of Ni-P Amorphous Alloy

Ni₈₁P₁₉ amorphous alloy was prepared by electro-deposition, and then was melt in arc furnace and cast in copper mold. Drop tube and fluxing process was used to study the containerless solidification behavior of Ni-P alloy, and the as solidified sample was analyzed and investigated by differential scanning calorimeter(DSC), X-ray diffractometer(XRD), optical microscope, and scanning electron microscope(SEM). Glass transformation temperature T_g, crystalline temperature T_x, peak temperature T_p1 and T_p2 were got by DSC analysis, and these parameters were fitted with Kissinger function, glass transformation activation energy E_g=374.8 KJ/mol and crystalline activation E_p1=148.9KJ/mol and E_p2=274.9 KJ/mol could be computed. These parameters showed that Ni-P amorphous alloy was liable to be crystallized easily. By casting in copper mold, Ni₈₁P₁₉ eutectic alloy was prepared, and the outcome of phases was Ni and Ni₃P compound, which were identified by XRD pattern. After fluxing process, anomalous eutectic microstructure could be observed in the as solidified sample, and model of dendrite remelting was used to explain this phenomenon. The as solidified droplets with diameter from 0.1mm to 2.0mm were achieved by drop tube. During the falling process, cooling rate determined the microstructure of the droplets. The microstructures were consisted of rod and anomalous eutectic phases. With the deceasing of diameter of droplet, both eutectic phases were refined which was caused by large undercooling rate. During the containerless solidification, Ni-P droplets with big size and large undercooling rate could easily be collected when the tube was filled with fixed inert gas of 5000Pa He and certain amount of Ar.