Crystallization behaviour of rapidly quenched and mechanically alloyed amorphous materials

Abstract

Amorphous metallic alloys were synthesized by the methods of rapid quenching and by mechanical alloying. In contrast to rapid quenching, mechanical alloying is a new process in producing amorphous alloys. In this paper we wilt report the amorphization of Ti-Cu, Hf-Cu, Hf-Ni and Fe-Ni-B alloys. The crystallization behaviour of these amorphous alloys was examined by DTA measurements with different heating rates in the range from 1 to 80 K / rain. The data of mechanically alloyed powders will be compared with those of rapidly quenched materials. Further characterizations were done by X-ray diffraction, SEM and EDAX analyses. In general, the examined amorphous materials prepared by mechanical alloying or rapid quenching show very similar properties.

Thermodynamic assessment of the copper-hafnium system

“…Hence, the ratio of thermodynamic stability of competing phases is important in the bulk decrystallization. Figure 5 shows that the concentration range of the [2][3][4] thermodynamic stability of supercooled molten alloys relative to solid solutions bounded with branches of the metastable liquidus is x Hf = 0.33-0.72. It satisfactory agrees with the experimental [31] concentration range of bulk decrystallization.…”

“…The boundary of this range is between the metastable liquidus line and the equality line of the free energies for the solid solution and melt ) ( / L 0 ϕ T [30]. temperatures T x for amorphous copper−hafnium alloys determined in [2][3][4]. Analysis of the phase boundaries between the supercooled melt and solid solutions based on pure components presented in Fig.…”