EFFECTS OF HYDROSTATIC-PRESSURE ON SOLID-STATE REACTION IN BINARY NANOSTRUCTURED TI60SI40 BLENDS

Nanocrystalline Ti60Si40 blends prepared by mechanical milling were tr eated under pressures of 2 to 7 GPa at temperatures below 400 degrees C. The phase compositions in the treated samples were identified by X- ray diffraction, scanning and transmission electron microscopy as well as differential scanning calorimetry, respectively. Experimental resu lts revealed that high-pressure treatment restrained the growth of nan ocrystals but favored the formation of a new metastable Ti-rich Ti-Si phase which has nucleated in the above nanometer-sized blends during m illing. The above solid-state reaction is kinetically limited and thus does not occur within the time frame of our experiments if the pressu re is larger than 4 GPa. Only the growth of nanocrystals but no reacti ons occurred for tile samples annealed at normal pressure.