Material Sciences
Vol. 08  No. 09 ( 2018 ), Article ID: 26931 , 7 pages
10.12677/MS.2018.89109

Study on the Crystallization Behavior of Fe-Based Amorphous Powder and Ribbon

Cuiqin Li1,2, Zhenghua Huang2, Chunjie Xu1, Zhongming Zhang1, Yuehua Kang2, Jianye Liu3, Gaofeng Hu3

1School of Materials Science and Engineering, Xi’an University of Technology, Xi’an Shaanxi

2Guangdong Province Key Laboratory for Technology and Application of Metal Toughening, Guangdong Institute of Materials and Processing, Guangzhou Guangdong

3Guangdong Hanbang Laser Technology Co. Ltd., Zhongshan Guangdong

Received: Aug. 21st, 2018; accepted: Sep. 18th, 2018; published: Sep. 25th, 2018

ABSTRACT

The phase composition and crystallization behavior of Fe50.6Cr23.3Mo8.4C8.4B9.3 (at.%) alloy powder and ribbon were analyzed by X-ray diffraction (XRD) and isochronous heating using differential scanning calorimetry (DSC). The results show that the powder and ribbon exhibit fully amorphous phase. All isochronal DSC curves exhibit an obvious glass transition, as well as two exothermic peaks corresponding to the precipitation of α-Fe and χ-Cr6Fe18Mo5 plus (Fe, Cr, Mo)7C3 phases respectively when heating temperature does not excess 993 K. Glass transition temperature Tg, crystallization onset temperature Tx, and two exothermic peak temperature Tp1, Tp2 of powder are all higher than that of ribbon by the improving amplitude of 6 - 15 K. However, the supercooled liquid region ΔTx is 71.4 K for powder, which is slightly lower than that for ribbon (78.6 K). Apparent activation energy Ea1 and Ea2 calculated according to Tp1 and Tp2 are 344.4 kJ/mol and 398.3 kJ/mol for powder, respectively, which is lower than that for ribbon which are 485.6 kJ/mol and 487.4 kJ/mol, respectively.

Keywords:Amorphous Alloy, Fe-Cr-Mo-C-B Alloy, Crystallization Behavior, Apparent Activation Energy

Fe基非晶粉末与薄带的晶化行为研究

李翠芹1,2,黄正华2*,徐春杰1,张忠明1,康跃华2,刘建业3,胡高峰3

1西安理工大学材料科学与工程学院,陕西 西安

2广东省材料与加工研究所 广东省金属强韧化技术与应用重点实验室,广东 广州

3广东汉邦激光科技有限公司,广东 中山

收稿日期:2018年8月21日;录用日期:2018年9月18日;发布日期:2018年9月25日

摘 要

利用X射线衍射(XRD)和差示扫描量热仪(DSC)分析了Fe50.6Cr23.3Mo8.4C8.4B9.3 (at.%)合金粉末和薄带的相组成和等时加热的晶化行为。结果表明,粉末和薄带为完全非晶态,所有的等时DSC曲线均显示出明显的玻璃转变。当加热温度不超过993 K时有两个放热峰,分别对应于α-Fe以及χ-Cr6Fe18Mo5和(Fe, Cr, Mo)7C3相的析出。粉末比薄带展示出更高的玻璃转变温度Tg、晶化开始温度Tx和两个放热峰峰值温度Tp1、Tp2,提高幅度约6~15 K。然而,粉末的过冷液相区宽度ΔTx为71.4 K,稍低于薄带(78.6 K)。由Tp1和Tp2计算的粉末的表观激活能Ea1和Ea2分别为344.4 kJ/mol和398.3 kJ/mol,低于薄带(485.6 kJ/mol和487.4 kJ/mol)。

关键词 :非晶合金,Fe-Cr-Mo-C-B合金,晶化行为,表观激活能

Copyright © 2018 by authors and Hans Publishers Inc.

This work is licensed under the Creative Commons Attribution International License (CC BY).

http://creativecommons.org/licenses/by/4.0/

1. 引言

自从1960年,Duwez等人 [1] 首次成功制备出Au-Si非晶合金,此事件引起世界各地研究者的广泛关注。非晶合金即金属玻璃,因其原子排列长程无序和短程有序,表现出一系列优异的力学性能、磁性能、电性能和电化学性能,因而被广泛应用于航空航天、汽车、精密制造、通讯设备、计算机和生物医学领域 [2] [3] [4] 。有些非晶合金系表现出磁晶各向异性和优异的软磁性能,有望成为结构材料应用于某些特殊领域 [5] 。通常,形成非晶合金的临界冷速高达102~104 K/s。所以,早期通过快速淬火倾向于制备薄箔、丝线和薄带,可使冷速达到105~106 K/s [5] [6] [7] ,这极大限制了非晶合金的进一步研究和应用。直到近十年来,非晶合金尺寸才达到块体级别。

Fe基非晶合金具有优异的玻璃形成能力(Glass Forming Ability, GFA)和软磁性能,如高饱和磁强度、低矫顽力、高电阻率和渗透性,能降低磁滞损耗和功率损耗,常用于制备电磁转换设备的铁芯 [8] [9] [10] 。1995年,Inoue等人 [11] 研究出Fe-(Al,Ga)-(P,C,B)系列块体非晶合金(Bulk Metallic Glasses, BMGs)。自此,开发大尺寸Fe基非晶合金成为研究热点之一。据报道,Fe基非晶合金固有高的GFA,表现在具有较大的临界铸造厚度 [12] [13] [14] 。Inoue等人 [15] 总结出具有高GFA的合金体系特点是:成分至少包含三种元素、原子尺寸配比大于12%、原子之间为负混合热。迄今为止报道的非晶合金的GFA依赖于Ga、Zr、Nb、Pd以及稀土元素Ln、Y、Pr等,但是其高昂的价格限制了广泛的商业应用 [16] 。目前聚焦于使用便宜、含量富足的B、C、Si和P元素来制备Fe基BMGs [17] 。此外,添加Mo元素可提高GFA、耐腐蚀性和耐磨性,使得硬度达到1500 HV [16] [18] 。添加Cr元素使得合金表面形成一层Cr2O3钝化膜而提高其耐腐蚀性、抗氧化性,以轻微降低GFA作为代价 [19] 。在冷却过程中添加大约20%的C、B、P、S等非金属元素来维持非晶结构的稳定性 [17] 。本文主要研究Fe50.6Cr23.3Mo8.4C8.4B9.3 (at.%)非晶粉末和薄带的晶化行为,探讨同一非晶合金在不同状态下的热稳定性差异,为后续不同应用场合提供技术支撑。

2. 实验方法

商用气雾化Fe50.6Cr23.3Mo8.4C8.4B9.3(at.%)粉末由Advanced Materials Engineering,LLC提供。在高纯氩气保护气氛下,在含有Ti吸气的真空电弧熔炼炉内重熔粉末以形成合金锭。接着,在单辊甩带设备上制备出厚30~35 μm、宽2~3 mm的薄带,其中,铜辊线速度为40 m/s。

利用JF-1166激光粒度测试仪测试粉末的粒径分布,并利用扫描电子显微镜(SEM, JEOL JXA-8100)观察粉末形貌。同时,测试粉末的流动性、松装密度和振实密度。在采用Cu靶的X射线衍射仪(XRD, SmartLab)上分析粉末和薄带的结构特征。非晶粉末和薄带的等时晶化过程在高纯氩气保护的Perkin-Elmer差示扫描量热仪(DSC, DSC8000)上进行。温度和热流分别通过测定纯In和Zn的熔化温度和熔化热予以标定,其误差分别为±0.3 K和±0.02 mW。每个试样均进行两次处理,第一次退火过程中试样发生晶化,第二次退火过程则是在试样已经完全晶化的情况下进行,以此作为热分析的基线。二次测量的热焓值之差即为消除系统偏移后的DSC实验值。

3. 结果与讨论

图1图2分别为Fe50.6Cr23.3Mo8.4C8.4B9.3粉末的SEM形貌照片和粒径分布。可见,粉末为大小均匀的球形颗粒,意味着流动性良好,其平均粒径、流动性、松装密度和振实密度分别为30 μm、18.5 s/50 g、4.55 g/cm3和4.84 g/cm3 (见表1)。

粉末和薄带的XRD谱均呈现一个较宽的漫散射峰,表明为典型的完全非晶(见图3)。

图4为Fe50.6Cr23.3Mo8.4C8.4B9.3粉末和薄带在加热速率为20 K/min下的等时DSC曲线,对应的玻璃转变温度Tg、晶化开始温度Tx、放热峰峰值温度Tp1、Tp2和过冷液相区宽度DTx列于表2中。可见,粉末和薄带的等时DSC曲线均呈现出明显的玻璃转变,在加热温度不超过993 K的情况下出现两个放热峰。根据文献 [10] ,这两个放热峰分别对应于α-Fe和χ-Cr6Fe18Mo5以及(Fe, Cr, Mo)7C3相的析出。相比于薄带,粉末呈现更高的Tg、Tx、Tp1和Tp2,提高幅度为6~15 K。然而,薄带呈现更高的过冷液相区宽度ΔTx (78.6 K),而粉末仅为71.4 K。

为了获得粉末和薄带结晶后的表观激活能,根据加热速率范围在10 K/min至40 K/min的等时DSC曲线得到的热力学参数。结合Kissinger方程确定表观激活能,方程如下 [20] :

Figure 1. SEM morphology of Fe50.6Cr23.3Mo8.4C8.4B9.3 powder

图1. Fe50.6Cr23.3Mo8.4C8.4B9.3粉末的SEM形貌

Table 1. Basic parameters of Fe50.6Cr23.3Mo8.4C8.4B9.3 powder

表1. Fe50.6Cr23.3Mo8.4C8.4B9.3粉末的基本参数

Figure 2. Particle size distribution of Fe50.6Cr23.3Mo8.4C8.4B9.3 powder

图2. Fe50.6Cr23.3Mo8.4C8.4B9.3粉末的粒径分布

Figure 3. XRD results of Fe50.6Cr23.3Mo8.4C8.4B9.3 powder and ribbon

图3. Fe50.6Cr23.3Mo8.4C8.4B9.3粉末和薄带的XRD结果

Figure 4. Isochronal DSC curves of Fe50.6Cr23.3Mo8.4C8.4B9.3 powder and ribbon at a heating rate of 20 K/min

图4. Fe50.6Cr23.3Mo8.4C8.4B9.3粉末和薄带在加热速率为20 K/min下的等时DSC曲线

Table 2. Corresponding thermodynamic parameters of Fe50.6Cr23.3Mo8.4C8.4B9.3 powder and ribbon at a heating rate of 20 K/min

表2. Fe50.6Cr23.3Mo8.4C8.4B9.3粉末和薄带在加热速率为20 K/min时对应的热力学参数

ln ( β T p 2 ) = E a R T p + ln K 0 (1)

式中:b是加热速率,Tp是放热峰的峰值温度,R是气体常数约8.314 J/(mol×K),K0是预指数因子常数,Ea是表观激活能——加热结晶时需要越过的能量势垒。 ln ( β / T p 2 ) 与−1/Tp产生的点拟合为一条直线,其斜率为Ea/R,斜率乘以R即可得到表观激活能Ea图5为Fe50.6Cr23.3Mo8.4C8.4B9.3粉末和薄带在不同加热速率下的等时DSC曲线。图6为Fe50.6Cr23.3Mo8.4C8.4B9.3粉末和薄带分别对应于第一和第二晶化反应的Kissinger曲线。经计算,粉末对应于第一放热峰和第二放热峰的表观活化能Ea1和Ea2分别为344.4 kJ/mol和398.3 kJ/mol。然而,薄带表现出更高的表观激活能,Ea1和Ea2分别增加到485.6 kJ/mol和487.4 kJ/mol,这与粉末和薄带的ΔTx趋势一致。粉末比薄带的ΔTx低,说明粉末的非晶结构没有薄带稳定,其弱的热稳性导致在加热时容易结晶,即激活能较低,越难保持非晶结构特征。

4. 结论

1) 等时DSC退火后,完全非晶的粉末和薄带均呈现明显的玻璃转变,当加热温度不超过993 K时出现两个放热峰。

2) 粉末较之于薄带表现出更高的玻璃转变温度、晶化开始温度和两个放热峰峰值温度,提高幅度在6~15 K。

Figure 5. Isochronal DSC curves of Fe50.6Cr23.3Mo8.4C8.4B9.3 powder (a) and ribbon (b) at different heating rates

图5. Fe50.6Cr23.3Mo8.4C8.4B9.3粉末(a)和薄带(b)在不同加热速率下的等时DSC曲线

Figure 6. Kissinger plots of Fe50.6Cr23.3Mo8.4C8.4B9.3 powder (a) and ribbon (b) for the first and second crystallization reactions

图6. Fe50.6Cr23.3Mo8.4C8.4B9.3粉末(a)和薄带(b)分别对应于第一和第二晶化反应的Kissinger曲线

3) 粉末的过冷液相区宽度ΔTx为71.4 K,稍低于薄带的78.6 K,这与粉末和薄带计算得到的表观激活能Ea相一致。粉末的表观激活能分别为344.4 kJ/mol和398.3 kJ/mol,而薄带的表观激活能分别提高至485.6 kJ/mol和487.4 kJ/mol。

基金项目

广东省稳定性支持项目(2017A070701029);广东省应用型科技研发专项(2015B090926001);广东省重大科技专项(2014B010131005和2016B090914001)。

文章引用

李翠芹,黄正华,徐春杰,张忠明,康跃华,刘建业,胡高峰. Fe基非晶粉末与薄带的晶化行为研究
Study on the Crystallization Behavior of Fe-Based Amorphous Powder and Ribbon[J]. 材料科学, 2018, 08(09): 939-945. https://doi.org/10.12677/MS.2018.89109

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