The Characteristics and Mechanisms of Ultra-Fine Grained Structure Formation during Severe Large Deformation.

剧烈大变形过程中超细晶结构形成的特征及机制。

基本信息

批准号：
16560627
负责人：
SAKAI Taku
金额：
$ 2.24万
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：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16560627/
关键词：
Hot working Warm and cold working Multidirectional forging Microshear band kink bands Grain fragmentation Continuous recrystallization Fine-grained structure 温間、冷間加工結晶粒内分割

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 ambient and high temperatures by using Al, Mg and Fe alloys. The relationships between deformation characteristics and evolution process of microstructures were analyzed, and the main results obtained were summarized as follows.1.The volume fraction of new fine-grained structure evolved by MDF increases more rapidly with deformation compared with that in a single pass compression. Increase in a strain per each MDF results in rapid evolution of finer grained structure in lower strain.2.During a single pass compression, in contrast, new grains are developed only along the original grain boundaries and fine layered microstructures are formed in the grain interiors.3.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.4.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.5.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.

研究了Al、Mg、Fe合金在常温和高温下的多向锻造（MDF）和单道次压缩过程中剧烈大变形过程中细晶结构的形成过程和机制。分析了变形特征与微观组织演化过程之间的关系，得到的主要结果总结如下：1.与单道次压缩相比，MDF演化出的新细晶组织的体积分数随变形增加更快。。每个 MDF 的应变增加会导致在较低应变下快速演化出更细的晶粒结构。 2. 相反，在单道压缩过程中，新晶粒仅沿着原始晶界生长，并在晶粒内部形成精细的层状微结构.3.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。其边界的密度和错误取向随着应变的增加而增加，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。4.在MDF过程中，变形带在三维空间的各个方向上发展，导致大尺寸细晶结构的形成。拉紧。这意味着MDF是细晶结构形成的有效方法之一。5.这种应变诱导晶粒结构的退火不能通过常规的不连续再结晶（包括新晶粒的形核和生长）来控制，还可以通过原位或连续再结晶来控制。静态再结晶，其中晶粒长大并伴随着回复。