Mechanisms of strain-induced grain structure formation-Reconsideration of recrystallization

应变诱导晶粒结构形成机制——再结晶的再思考

基本信息

批准号：
18560689
负责人：
SAKAI Taku
金额：
$ 2.46万
依托单位：
The University of Electro-Communications
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

The process and mechanisms of fine-grained structure formation during severe large deformation was studied in multi-Directional forging (MDF) and a single pass compression at low and high temperatures by using Cu and Al, Mg and Fe alloys. The relationships between deformation characteristics and evolution process of microstructures were systematically analyzed, and the main results obtained were summarized as follows.1. Several kinds of deformation bands such as microshear and kink bands are generated in grain interiors in above a critical strain. The density and the misorientations of their boundaries increase with straining, leading to fragmentation of original grain interiors and finally formation of new fine-grains. The process of such strain-induced grain formation is concluded to be controlled by in-situ or continuous dynamic recrystallization.2. Deformation bands are developed in various directions in three-dimensional space during MDF, leading to formation of fine-grained structures in large strain. This means that MDF is one of effective methods for fine-grained structure formation.3. The process of new fine grain formation in a wide temperature interval can be classified into the three stages : (1) formation of conventional dislocation substructures accompanied with embryos of deformation bands (DBs) in stage 1 (ε<2) ; (2) development of large scale DBs followed by grain fragmentation, leading to new grain formation along DBs at moderate strains in stage 2 (2<ε<4) ; (3) development of new grained structures at high strains in stage 3 (ε>4).4. Annealing of such strain-induced grain structure can not be controlled by conventional discontinuous recrystallization including nucleation and growth of new grains, but also by in-situ or continuous static recrystallization, in which grain growth takes place accompanied with recovery.

利用Cu与Al、Mg、Fe合金，研究了多向锻造(MDF)和低温、高温单道次压缩过程中剧烈大变形过程中细晶组织形成的过程和机制以及变形特性之间的关系。系统地分析了微观结构的演化过程，得到的主要结果概括如下： 1．在临界应变以上，晶粒内部会产生微剪切带、扭结带等多种变形带。其边界的错误取向随着应变而增加，导致原始晶粒内部破碎并最终形成新的细晶粒。这种应变诱导晶粒形成的过程被认为是由原位或连续动态再结晶控制的。2． MDF过程中能带在三维空间中向各个方向发展，导致大应变下细晶结构的形成，这意味着MDF是细晶结构形成的有效方法之一。 3．较宽温度范围内的细晶粒形成可分为三个阶段：（1）常规位错亚结构的形成，并伴随第一阶段变形带（DB）的胚（ε<2）；（2）大尺度DB的发展；随后是晶粒破碎，导致在第 2 阶段中中等应变下沿 DB 形成新晶粒 (2<ε<4)； (3) 在第 3 阶段中高应变下 (ε>4) 形成新晶粒结构。 4．这种应变诱发的晶粒结构不能通过传统的不连续再结晶（包括新晶粒的成核和生长）来控制，也不能通过原位或连续静态再结晶来控制，其中晶粒生长伴随着回复而发生。