In-situ observation of an unusual phase transformation pathway with Guinier-Preston zone-like precipitates in Zr-based bulk metallic glasses
In-situ observation of an unusual phase transformation pathway with Guinier-Preston zone-like precipitates in Zr-based bulk metallic glasses
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原位观察锆基块体金属玻璃中吉尼尔-普雷斯顿区状析出物的不寻常相变途径
DOI：
10.1016/j.jallcom.2019.153049
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发表时间：
2020-04-05
影响因子：
6.2
通讯作者：
Wang, Xun-Li
中科院分区：
文献类型：
--
作者：
Dong, Weixia;Ge, Jiacheng;Wang, Xun-Li
采用原位技术研究了Zr52.5Cu17.9Ni14.6Al10Ti5大块非晶合金的非晶-晶相变途径。多尺度结构的证据揭示了一个五阶段的途径，类似于非平衡的转变过程中的Guinier-Preston区在沉淀硬化合金的时效过程中，通过以下顺序后，等温退火的合金在过冷液体区域：多晶相变，化学相分离，形成一个有序性差的亚稳相，并形成最终的结晶产品。在不同的退火温度下，多变的孕育期，和突然的多尺度结构的变化，以及在量热测量中的潜热释放，支持在早期阶段的相变的一阶性质。实空间的结构演化表明，在相变的早期阶段，团簇连接性在中程尺度上的增强起着至关重要的作用，而界面限制有序化在相变的后期阶段起着主导作用.实验结果表明，相变过程中“Guinier-Preston区”析出相伴随着有序参数梯度扩散界面核壳结构的运动学发展，使得合金体系的自由能在相变过程中逐步降低，这可能是具有优良玻璃形成能力的多元Zr基合金的特征行为。(C)2019 Elsevier B. V.版权所有。
The pathway of amorphous-to-crystalline phase transformation in Zr52.5Cu17.9 Ni14.6Al10Ti5 bulk metallic glasses was studied using a suite of in-situ techniques. Multi-scale structure evidence reveals a five-stage pathway, analogous to the non-equilibrium transformation process with Guinier-Preston zones during aging in precipitation-hardened alloys, by the following sequence upon isothermal annealing the alloy in the supercooled liquid region: polyamorphous phase transition, chemical phase separation, the formation of a poorly-ordered metastable phase, and the formation of a final crystalline product. The changeable incubation periods at different annealing temperatures, and the abrupt multi-scale structure changes, as well as a latent heat release in the calorimetric measurements, support the first-order nature of the phase transformation at early stages. The structure evolution in real-space indicates that the enhancement of cluster connectivity on the medium-range scale plays essential roles in the early stages of the phase transformation, while the interface-limited ordering dominates the later stages. The experimental results suggest the phase transformation pathway with "Guinier-Preston zone-like" precipitates accompanied by the kinematic development of core-shell structures of diffuse interfaces with order parameters gradients, enabling the step-by-step decrease of free energy of the alloy system during phase transformation, which might be a characteristic behavior for multicomponent Zr-based alloys with excellent glass-forming ability. (C) 2019 Elsevier B.V. All rights reserved.