Crystallization kinetics and glass-forming ability of bulk metallic glassesPd40Cu30Ni10P20andZr41.2Ti13.8Cu12.5Ni10Be22.5from classical theory

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Due to their scientific significance and potential engineering applications, bulk metallic glasses are among the most intensively studied advanced materials. Understanding the glass-forming ability (GFA) of these metallic alloys is a long-standing subject. While a large number of empirical factors have been proposed to correlate with GFA of the alloys, a full understanding of GFA remains a goal to achieve. Since glass formation is a competing process against crystallization, we have performed a systematic analysis on the crystallization kinetics of two known best metallic glass-formers ${\mathrm{Pd}}_{40}{\mathrm{Cu}}_{30}{\mathrm{Ni}}_{10}{\mathrm{P}}_{20}$ (in at. %) and ${\mathrm{Zr}}_{41.2}{\mathrm{Ti}}_{13.8}{\mathrm{Cu}}_{12.5}{\mathrm{Ni}}_{10}{\mathrm{Be}}_{22.5}$ based on classical nucleation and growth theory. Our results show that there is a dramatic difference between the two alloys in their nucleation behavior although they possess comparable GFA. Particularly, an extremely sharp nucleation peak ($\ensuremath{\sim}{10}^{18}∕{\mathrm{m}}^{3}\phantom{\rule{0.2em}{0ex}}\mathrm{s}$) is found for ${\mathrm{Pd}}_{40}{\mathrm{Cu}}_{30}{\mathrm{Ni}}_{10}{\mathrm{P}}_{20}$ around $632\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ with a very small half maximum width of $42\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, implying that this alloy is an excellent candidate for nanocrystallization studies. Moreover, we have also found that the GFA of these alloys can be calculated to a high accuracy and precision based on the classical theory, suggesting that the classical theory may be sufficient to account for glass formation mechanism in these metallic alloys.