Crystallization process in rapidly solidified Al-Nd-Ni
amorphous alloy prepared by melt spinning①
amorphous alloy prepared by melt spinning①
(School of Materials Science and Engineering, Central South University,
Changsha 410083, China)
Changsha 410083, China)
Abstract: Rapidly solidified ribbons of Al90Nd7Ni3metallic glasses were prepared by using melt spinning. Crystallization process of the totally amorphous ribbons was investigated by differential scanning calorimetry and X-ray diffraction analysis, under continuous heating regime. The results show that, under continuous heating regime, the metallic glass devitrifies via two main stages: primary crystallization, resulting in two-phase mixture ofα(Al) plus residual amorphous phase,
and secondary crystallization, corresponding to some inter-metallic phases appearing, successively including Al11Nd3, Al3Ni, and some unknown phases, in the Al amorphous/crystal matrix. Four peaks appear on the continuous heating DSC curves. Their peak temperatures are respectively 470.8, 570.8, 585.6, and 731.6 K at infinitesimal heating rate, and their activation energies of the respective phase transformation are 183.0, 294.7, 232.5 and 269.1 kJ/mol. The values of Avrami exponent of the four reactions decrease with increasing relative transformation degree. At the earlier stage of phase transformation, the values ofnare larger than 4, and at the later stage the values ofnbecome close to some value from 0.5 to 2.0.
and secondary crystallization, corresponding to some inter-metallic phases appearing, successively including Al11Nd3, Al3Ni, and some unknown phases, in the Al amorphous/crystal matrix. Four peaks appear on the continuous heating DSC curves. Their peak temperatures are respectively 470.8, 570.8, 585.6, and 731.6 K at infinitesimal heating rate, and their activation energies of the respective phase transformation are 183.0, 294.7, 232.5 and 269.1 kJ/mol. The values of Avrami exponent of the four reactions decrease with increasing relative transformation degree. At the earlier stage of phase transformation, the values ofnare larger than 4, and at the later stage the values ofnbecome close to some value from 0.5 to 2.0.
Key words: rapid solidification; Al-riched amorphous alloy; crystallization process; phase transformation