Development of a novel microstructure controlling process for high performance materials using severe -plastic-deformation

利用严重塑性变形开发高性能材料的新型微观结构控制工艺

基本信息

批准号：
14550693
负责人：
AMEYAMA Kei
金额：
$ 2.18万
依托单位：
Ritsumeikan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550693/
关键词：
Powder Metallurgy Steels Mechanical Alloying Nano structure Stacking Fault Energy Phase Transformation Austenitic Stainless Steel NIckel 超強化工ステンレス鋼超微細結晶粒ナノ構造制御微細組織 SUS316 フェライト

项目摘要

Formation mechanism and microstructure of severe plastic deformed materials such as 5U5316L austenitic stainless steels and Nickel are studied. Mechanical Milling (MM) process is one of the severe plastic deformation (SPD) process which enables to produce an ultra fine grain structure. By the TEM, formation of an equiaxed grain structure with high dislocation density and its grain size of less than 100 nm are observed. The SADP demonstrates that the microstructure consists of FCC and BCC crystal structures. These FCC and BCC grains show almost the same grain size, however, the image of the BCC grain is more spherical and more clear than that of the FCC grain. In other words, compared to the BCC grain the FCC grain has more irregular grain boundary and more complex strain contrast. The Vickers hardness tests of as homogenized, as milled and annealed (at 358 K (85 degree C) for 5 mm or 1 hr) powders indicates a large decrease in the hardness after annealing at 358 K. The results strongly suggest that there must exist of a huge number of vacancies to cause such a low temperature recovery. These results also imply that the BCC phase appears by means of a diffusionless transformation. Although the austenite phase in the 5U5316L steel is meta-stable at the room temperature, it hardly transforms to martensite phase even by a heavy deformation. Thus, the BCC phase is considered to form by a massive-like ferrite transformation. The spherical shape of the ferrite grain is attributed by the nucleation and growth of the massive ferrite grain. The increase of lattice defects, which leads to low temperature recovery, and formation of the irregular grain boundary structure result in increase of driving force for the transformation of austenite to ferrite.

研究了5U5316L奥氏体不锈钢、镍等严重塑性变形材料的形成机理和显微组织。机械铣削（MM）工艺是剧烈塑性变形（SPD）工艺之一，能够产生超细晶粒结构。通过TEM观察到形成高位错密度的等轴晶结构，其晶粒尺寸小于100 nm。 SADP 表明微观结构由 FCC 和 BCC 晶体结构组成。这些 FCC 和 BCC 颗粒显示出几乎相同的颗粒尺寸，但是，BCC 颗粒的图像比 FCC 颗粒更接近球形且更清晰。换句话说，与BCC晶粒相比，FCC晶粒具有更不规则的晶界和更复杂的应变对比。对均质化、研磨和退火（358 K（85 摄氏度）5 毫米或 1 小时）粉末的维氏硬度测试表明，358 K 退火后硬度大幅下降。结果强烈表明，一定存在大量的空缺导致如此低温的复苏。这些结果还意味着 BCC 相是通过无扩散转变出现的。尽管5U5316L钢中的奥氏体相在室温下是亚稳定的，但即使发生严重变形，也很难转变为马氏体相。因此，BCC相被认为是通过块状铁素体相变形成的。铁素体晶粒的球形形状归因于块状铁素体晶粒的形核和生长。晶格缺陷的增加导致低温回复，不规则晶界结构的形成导致奥氏体向铁素体转变的驱动力增加。