Thermodynamic study on grain boundary segregation

2015 Fiscal Year Final Research Report

• Project/Area Number: 24360265
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Physical properties of metals
• Research Institution: Tohoku University (2013-2015); Kyushu Institute of Technology (2012)
• Principal Investigator: OHTANI HIROSHI 東北大学, 多元物質科学研究所, 教授 (70176923)
• Co-Investigator(Kenkyū-buntansha): TOKUNAGA Tatsuya 九州工業大学, 工学研究院, 准教授 (40457453) ; IIKUBO Satoshi 九州工業大学, 生命体工学研究科, 准教授 (40414594)
• Project Period (FY): 2012-04-01 – 2016-03-31
• Keywords: 金属物性 / 熱力学 / 格子欠陥 / 粒界構造 / アモルファス

Outline of Final Research Achievements

We employed a simple physical model of a grain boundary in discussing the segregation of alloying elements in iron, stating that the grain boundary has a constant thickness and that Gibbs energy can be assigned to the boundary material. The regular solution model was applied to the bulk and the grain boundary, and in particular, the Gibbs energy of the grain boundary was expressed as that of the liquid phase in Fe-based binary systems. It seems unusual to apply the Gibbs energy of a liquid to a grain boundary; however, it could be reasonable when considering the structural analogy between an amorphous phase and a grain boundary composed of simple structural units. In fact, the calculated segregation coefficient of boron agrees fairly well with the experimental value. The result provides us with an insight into grain-boundary segregation as an ordering process, where the added element is placed in the vacant site in polyhedral clusters.

Free Research Field

工学