Abstract
Cut pieces of cast Mg2Ni ingot were heated in a vacuum of about 10−2 Pa for 1.8∼14.4 ks at 773, 823 and 873 K, and then examined using X-ray diffraction, optical microscopy and electron probe X-ray microanalyzer with EDX. The vacuum heating resulted in the demagnesization of Mg2Ni phase by sublimation of magnesium from the surface, forming porous layer of MgNi2. Thickness of the layer increased with increasing temperature and/or heating time. Approximate estimation, using these kinetic data, showed that apparent activation energy of the growth of the layer was 210 kJ/mol. Based on the estimation, the whole Mg2Ni specimen with 0.7 × 10−3 m thickness was found to change into the porous MgNi2 after vacuum-heating for 14.4 ks at 923 K.
