Interfacial reactions between Ti-6Al-4V alloy and zirconia mold during casting

摘要

The interface of Ti-6Al-4V casting and ZrO2 moldwith silica binder was investigated by using electron probemicroanalyses (EPMA), X-ray diffraction (XRD), and analyticaltransmission electron microscope (TEM). The interfacial reactionswere proceeded by the penetrationof liquid titanium through openpores near the mold surface. The metal side consisted of an α-phase layer on the top of the typical α+βtwo-phase substrate. Inthe ceramic side,zirconia was reduced by titanium to form oxygen-deficient zirconia ZrO2-x and evolved a gaseous phase (presumablyoxygen). The SiO2 binder, dissolved in the ZrO2 mold, could reactwith titanium to form Ti5Si3 in the metal side. Meanwhile,titanium could transform to titanium suboxides TiyO(y≥2) andthe lower phase boundary of cubic ZrO2-x was shifted to ZrO1.76.Some amount of the stabilizer CaO, dissolved in Ti along withZrO2, could react with Ti(O) to form Ca3Ti2O7 and CaAl4O7 in the reaction zone.