Analysis on dislocation theory model for local deformation behavior in bcc metal through TEM in-situ straining technique

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01696
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 26010:Metallic material properties-related
• Research Institution: National Institute for Materials Science
• Principal Investigator: OHMURA Takahito 国立研究開発法人物質・材料研究機構, 構造材料研究拠点, 副拠点長 (40343884)
• Co-Investigator(Kenkyū-buntansha): 井 誠一郎 国立研究開発法人物質・材料研究機構, 構造材料研究拠点, 主幹研究員 (60435146)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 転位 / BCC金属 / 塑性変形 / 局所力学挙動 / TEM / 粒界

Outline of Final Research Achievements

TEM in-situ straining measurements for interstitial-free steel revealed that dislocations in grain interior moved to a grain boundary and were absorbed at the grain boundary during deformation. The corresponding stress-strain relation showed remarkable stress increase due to the reduction of the dislocation density. For further deformation stage, dislocations nucleated at a grain boundary to lead an increase in dislocation density. Nanoindentation measurements for Fe single crystal revealed that the strain burst phenomenon occur at the transition from elastic to plastic deformation, which showed a Gaussian distribution of probability density. In the subsequent stage of the deformation, the strain burst phenomenon presented power-law function, which is totally different physical model of the deformation.

Free Research Field

材料強度物性

Academic Significance and Societal Importance of the Research Achievements

bcc金属は，鉄鋼材料に代表されるように身近な構造材料であり，社会インフラを支える重要な役割を果たしている。学術的には，bcc結晶構造に特有の転位運動と力学挙動の関係をTEM内その場変形などの先進的な手法によって直接的に捉えることに成功し，塑性変形の機構を解明した。社会的には，変形機構の基礎的な解明によって機械的性質のさらなる性能向上を実現する指針の構築に貢献した。