抄録
Structural relaxation in amorphous Ni50Ti50 alloy prepared by mechanical alloying has been investigated by differential scanning calorimetry and X-ray diffraction analysis. An exothermic DSC peak originating from structural changes in the amorphous state was observed with alloys milled after completion of amorphization. The peak was characterized by the increase in the intensity with milling time and reduced heating rate, and also with accompanying formation of phases such as NiTi2 and Ni3Ti with compositions different from the original one after crystallization. The kinetics of the reaction taking place at the peak was expressed by the Johnson-Mehl-Avrami equation with the Avrami exponent of 0.57. The origin of the peak was discussed with respect to the free energy diagram of Ni–Ti system. Structural relaxation was considered to take place at the peak to stabilize the configuration in the as-milled alloy, and to enhance phase separation or compositional fluctuation during milling.
