Beating Homogeneous Nucleation and Tuning Atomic Ordering in Glass-Forming Metals by Nanocalorimetry.
Beating Homogeneous Nucleation and Tuning Atomic Ordering in Glass-Forming Metals by Nanocalorimetry.
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DOI：
10.1021/acs.nanolett.7b03952
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发表时间：
2017-11
期刊：
影响因子：
10.8
通讯作者：
Bing Zhao;Bin Yang;A. Abyzov;J. Schmelzer;J. Rodríguez-Viejo;Q. Zhai;C. Schick;Yulai Gao
中科院分区：
文献类型：
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作者：
Bing Zhao;Bin Yang;A. Abyzov;J. Schmelzer;J. Rodríguez-Viejo;Q. Zhai;C. Schick;Yulai Gao
本文采用纳米量热法原位制备了Ce 68 Al 10 Cu 20 Co2（atom %）非晶合金。该技术可获得的高冷却和加热速率有利于抑制冷却时的结晶和均匀成核的识别。不同于一般认为金属玻璃是通过避免晶化而形成的观点，本文详细阐述了形核和生长在非晶合金晶化行为中的作用，从而为获得理想的无晶核金属玻璃提供了可能。局域原子组态对于揭示金属玻璃的玻璃形成能力和相变具有重要意义。出于这个原因，淬火后在Tg附近从0.001 s到25，000 s的等温退火成为调整局部原子构型并依次促进非晶合金、混合玻璃-纳米晶状态和结晶样品的策略。基于再加热过程中的晶化焓和总潜热的变化，我们对非晶合金等温形核和晶化的机理进行了定量分析。用Johnson-Mehl-Avrami方法研究了玻璃的等温晶化过程，结果表明，玻璃的等温晶化过程是均匀形核和非均匀形核共存的过程。过冷液体的等温结晶主要是非均匀形核而不是均匀形核。对于混合玻璃-纳米晶结构，一个非凡的动力学稳定性的残余玻璃被验证，这是归因于非晶相和有序纳米晶之间的致密填充界面。通过纳米量热法定制非晶结构，可以对解开GFA和金属玻璃中局部原子构型和相变的相关机制有新的见解。
In this paper, the amorphous Ce68Al10Cu20Co2 (atom %) alloy was in situ prepared by nanocalorimetry. The high cooling and heating rates accessible with this technique facilitate the suppression of crystallization on cooling and the identification of homogeneous nucleation. Different from the generally accepted notion that metallic glasses form just by avoiding crystallization, the role of nucleation and growth in the crystallization behavior of amorphous alloys is specified, allowing an access to the ideal metallic glass free of nuclei. Local atomic configurations are fundamentally significant to unravel the glass forming ability (GFA) and phase transitions in metallic glasses. For this reason, isothermal annealing near Tg from 0.001 s to 25,000 s following quenching becomes the strategy to tune local atomic configurations and facilitate an amorphous alloy, a mixed glassy-nanocrystalline state, and a crystalline sample successively. On the basis of the evolution of crystallization enthalpy and overall latent heat on reheating, we quantify the underlying mechanism for the isothermal nucleation and crystallization of amorphous alloys. With Johnson-Mehl-Avrami method, it is demonstrated that the coexistence of homogeneous and heterogeneous nucleation contributes to the isothermal crystallization of glass. Heterogeneous rather than homogeneous nucleation dominates the isothermal crystallization of the undercooled liquid. For the mixed glassy-nanocrystalline structure, an extraordinary kinetic stability of the residual glass is validated, which is ascribed to the denser packed interface between amorphous phase and ordered nanocrystals. Tailoring the amorphous structure by nanocalorimetry permits new insights into unraveling GFA and the mechanism that correlates local atomic configurations and phase transitions in metallic glasses.