Effect of Carbon on Nano-Crystallization in Steel during Mechanical Milling Treatment
Effect of Carbon on Nano-Crystallization in Steel during Mechanical Milling Treatment
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DOI：
10.2320/matertrans.44.1912
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发表时间：
2003-10
影响因子：
1.2
通讯作者：
H. Hidaka;K. Kawasaki;T. Tsuchiyama;S. Takaki
中科院分区：
文献类型：
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作者：
H. Hidaka;K. Kawasaki;T. Tsuchiyama;S. Takaki
金属粉末的机械球磨（MM）处理适合于制备纳米晶材料，因为钢球的球磨作用能够使粉末颗粒产生具有多方向塑性变形的巨大应变。本文研究了碳对高纯铁材料和铁碳材料MM处理过程中晶粒细化行为的影响。本研究中使用的粉末是电解纯铁（9 ppmC）和碳酸盐（6.2mass%C）粉末颗粒。将粉末混合以将化学组成设定为Fe-（0-2）质量%C。将混合粉末进行不同时间（3.6-360 ks）的MM处理，然后通过X射线衍射、TEM观察来检查显微结构。经MM处理后，铁素体分解为铁素体基体，经360 ks MM处理后获得铁素体单一组织。另一方面，铁素体组织通过动态连续再结晶（DCR）由位错胞状组织向细晶组织发展。随着MM处理的进行，晶粒尺寸逐渐减小。但高纯铁和铁碳材料达到稳态后的晶粒尺寸不同。随着碳含量的增加，经360 ksMM处理后的晶粒尺寸减小，Fe-0.8mass%C合金获得了晶粒尺寸约为15 nm的纳米晶组织。这表明碳的加入增强了晶粒细化，并且是通过剧烈塑性变形进行纳米晶化所必需的。考虑到碳原子与位错之间的相互作用，碳的加入有助于位错储存的增加，从而有助于DCR。这导致了在加碳铁中形成纳米晶结构的有效性。
Mechanical milling (MM) treatment of metallic powder is suitable for fabricating nano-crystallized materials, because milling action by steel balls enables to give a huge amount of strain with multi-directional plastic deformation to powder particles. In this study, effect of carbon on the grain refining behavior during MM treatment was investigated in high purity iron material and Fe-C materials. The powder used in this study is electrolytic pure (9 ppmC) iron and cementite (6.2mass%C) powder particles. The powders are mixed to set the chemical composition to be Fe-(0-2)mass%C. The mixed powder is subjected to MM treatment for various times (3.6-360 ks) and then microstructure was examined by means of X-ray diffractometry, TEM observation. With MM treatment, cementite decomposes into ferrite matrix and ferritic single structure is obtained after 360 ks MM treatment. On the other hand, microstructure of ferrite develops from dislocation cells structure to fine-grained structure through dynamic continuous recrystallization (DCR). The grain size is reduced gradually with MM treatment. However the grain size after reaching steady state is different between high purity iron and Fe-C materials. The grain size after 360 ks MM treatment decreases with increasing carbon content, and nano-crystallized structure with about 15 nm grain size was obtained in the Fe-0.8mass%C. This indicates that carbon addition enhances grain refining and is necessary for nano-crystallization by severe plastic deformation. Considering the interaction between carbon atoms and dislocations, carbon addition would assist the increment of stored dislocations which contributes to DCR. This results in the effectiveness for the formation of nano-crystallized structure in carbon added iron.