AMORPHIZATION REACTION OF NI-TA POWDERS DURING MECHANICAL ALLOYING

This study examined the amorphization behavior of NixTa100-x alloy pow ders synthesized by mechanically alloying (MA) mixtures of pure crysta lline Ni and Ta powders with a SPEX high energy ball mill. According t o the results, after 20 hours of milling, the mechanically alloyed pow ders were amorphous for the composition range between Ni10Ta90 and Ni8 0Ta20. A supersaturated nickel solid solution formed for Ni90Ta10 as w ell. X-ray diffraction analysis reveals two different types of amorphi zation reactions. Through an intermediate solid solution and by direct formation of amorphous phase. The thermal stability of the amorphous powders was also investigated by differential thermal analysis. As the results demonstrated, the crystallization temperature of amorphous Ni -Ta powders increased with increasing Ta content. In addition, the act ivation energy of amorphous Ni-Ta powders reached a maximum near the e utectic composition.