Non-isothermal crystallization kinetics of a Fe-Cr-Mo-B-C amorphous powder
Non-isothermal crystallization kinetics of a Fe-Cr-Mo-B-C amorphous powder
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Fe-Cr-Mo-B-C非晶粉末的非等温结晶动力学
DOI：
10.1016/j.jallcom.2020.153783
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发表时间：
2020-05-15
影响因子：
6.2
通讯作者：
Eckert, J.
中科院分区：
文献类型：
--
作者：
Dong, Q.;Song, P.;Eckert, J.
Fe-Cr-Mo-B-C非晶粉末通常用于热喷涂、放电等离子烧结或3D打印，以制备涂层或大尺寸块体非晶合金。但由于其结晶行为相对复杂，非等温结晶动力学研究还很不深入。采用X射线衍射、扫描电镜和差示扫描量热法，结合Ozawa法和局部Avrami指数，对Fe-Cr-Mo-B-C（Cr：25-27 wt%，Mo：16-18 wt%，B：2- 2.2 wt%，C：2-2.5 wt%）非晶粉末非等温晶化过程的相演变、晶化动力学和晶化机理进行了研究。第一沉淀相的峰值温度对加热速率不太敏感。在非等温结晶过程中，当恒速加热到高温时，相序列为：α-Fe，M-23（C，B）（6），M_7 C_3和FeMo_2B_2（M = Fe，Cr，Mo）。用Kissinger方法得到的非晶粉末的晶化表观活化能在385 ~ 557 kJ/mol之间，高于目前报道的大多数铁基非晶合金的晶化表观活化能，表明其具有较高的抗晶化稳定性。a-Fe和FeMo 2B 2具有相似的相变机制：早期相变是通过扩散控制生长完成的，形核速率增大;随着晶化体积分数的增加，形核速率减小，即使在晶化后期也不会发生形核。M-23（C，B）（6）和M7 C3的结晶机理相似：当结晶体积分数α高于0.1时，仅发生晶体生长。这可能是由于在早期沉淀相和无定形基质之间形成的大量界面促进成核，使得成核在结晶体积分数α小于0.1的阶段完成。因此，第一和第四结晶事件是扩散控制的，第二和第三结晶事件主要由晶粒生长控制。(C)2020 Elsevier B. V.保留所有权利。
Fe-Cr-Mo-B-C amorphous powders are usually used in thermal spraying, spark plasma sintering or 3D printing to prepare coatings or large-sized bulk amorphous alloys. However, their non-isothermal crystallization kinetics is far from being investigated in detail because of their relatively complicated crystallization behavior. In this work, the phase evolution, crystallization kinetics and crystallization mechanism of Fe-Cr-Mo-B-C (Cr: 25-27 wt%, Mo: 16-18 wt%, B: 2-2.2 wt%, C: 2-2.5 wt%) amorphous powder during non-isothermal crystallization are analyzed by X-ray diffraction, scanning electron microscope and differential scanning calorimetry together with Ozawa method and local Avrami exponent. The peak temperature of the first precipitated phase is less sensitive to the heating rate. In the non-isothermal crystallization process upon constant-rate heating to elevated temperatures the phase sequence is: alpha-Fe, M-23(C, B)(6), M7C3 and FeMo2B2 (M = Fe, Cr, Mo). The apparent activation energy of crystallization of the amorphous powders obtained using Kissinger's method is between 385 and 557 kJ/mol, which is higher than that of most iron-based amorphous alloys reported so far, indicating a relatively high stability against crystallization. a-Fe and FeMo2B2 have a similar transformation mechanism: the early phase transition is completed by diffusion controlled growth with an increasing nucleation rate; as the crystallized volume fraction increases, the nucleation rate decreases, and nucleation does not occur even in the later stage of crystallization. The crystallization mechanism of M-23(C, B)(6) and M7C3 is similar: when the crystallized volume fraction alpha is higher than 0.1, only crystal growth occurs. This might be due to the fact that the large number of interfaces formed between the early precipitated phase and the amorphous matrix promote nucleation, rendering nucleation complete at the stage when the crystallized volume fraction alpha is less than 0.1. Therefore, the first and fourth crystallization events are diffusion controlled, the second and third crystallization events are primarily governed by grain growth. (C) 2020 Elsevier B.V. All rights reserved.