TEMPERATURE-DEPENDENCE OF MECHANICAL ALLOYING AND GRINDING IN NI-ZR, CU-TA AND FE-B ALLOY SYSTEMS

The ambient temperature effect on the mechanical alloying and mechanical grinding processes was studied, using a mixture of nickel and zirconium powders (DELTA-H(mix) < 0), that of copper and tantalum powders (DELTA-H(mix) > 0) and the Fe2B compound. We confirmed in the Ni-Zr system that the higher the ambient temperature, the faster the amorphization proceeds. This temperature effect is observed as soon as mechanical alloying starts. The temperature effect exists also in the Cu30Ta70 powders but becomes noticeable after the average grain size is reduced below 100 angstrom. Hence, we believe that the retarded temperature effect is unique to a system with a positive heat of mixing. Neither the formation of an amorphous phase nor a sizable temperature effect is observed in the mechanical grinding process of the Fe2B compound.