FABRICATION AND MICROSTRUCTURE OF ZRO2-NI FUNCTIONAL GRADIENT MATERIAL BY POWDER-METALLURGY

Functional gradient material (FGM) of the ZrO2-Ni system was developed by a powder metallurgical process, and investigated for its microstru cture by means of X-ray diffractometry (XRD), electron probe microanal ysis (EPMA), transmission electron microscopy (TEM) and optical micros copy. It was shown that the sintered body of ZrO2-Ni FGM is almost ful ly densified, and its chemical composition and microstructure have the expected gradient distribution. With composition variation, the micro structure changes gradually from zirconia particles dispersed in a nic kel matrix to the converse with nickel particles dispersed in a zircon ia matrix, with network structures in the intermediate composition ran ge. Therefore, no distinct interfaces appear in the FGM due to the gra dient change of components, that is, both zirconia and nickel are pres ent everywhere in the microstructure. In phase composition, the sinter ed ZrO2-Ni FGM consists of nickel, tetragonal zirconia and a little mo noclinic zirconia. No reaction between nickel and zirconia has been de tected. The substructure of nickel and monoclinic zirconia are twins, and strain fringes can also be found in zirconia.