Low-temperature deformability of brittle intermetallics and its engineering applications

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H00824
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 26:Materials engineering and related fields
• Research Institution: Kyoto University
• Principal Investigator: INUI HARUYUKI 京都大学, 工学研究科, 教授 (30213135)
• Co-Investigator(Kenkyū-buntansha): 岸田 恭輔 京都大学, 工学研究科, 准教授 (20354178)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 低温変形能 / マイクロピラー / 降伏応力 / サイズ依存性 / 転位核生成 / 臨界体積 / 脆性材料 / 転位

Outline of Final Research Achievements

Low-temperature deformability has been investigated for brittle intermetallic materials that do not exhibit deformability at ambient temperature in the bulk form, by means of micropillar compression testing. Low-temperature deformability is observed not only for sigma-phase and Laves-phase intermetallics, embrittlement phases in steels but also a cementite-phase carbide, strengthening phase in in pearlite steel. In cementite, brittle failure does not occur for specimens in the wide range of specimen size, but the propensity for brittle failure increases in the sigma-phase intermetallic and in the Laves-phase intermetallic more significantly. This is due to the decreased fracture toughness that causes a smaller critical notch size for brittle failure to occur before the stress reaches the level for dislocation generation.

Free Research Field

材料物性

Academic Significance and Societal Importance of the Research Achievements

バルクでは発現しない脆性材料の低温変形能という現象そのものが新規な発見で学術的独自性が非常に高いが，その発現は原子が協調的励起を受けている体積に対応する転位核生成の臨界体積により記述でき，これを微小な試験片体積で高い応力レベルの実験ができるマイクロピラー試験によって実験的に評価する点に高い創造性があり，学術的意義がある．ラーベス相，シグマ相などの脆性金属間化合物の低温変形能の発現を調べ，この低温変形能のメカニズム解明を通して，脆性破壊が生じる臨界サイズが解明され，オーステナイト系耐熱鉄鋼材料おけるこれらGCP相金属間化合物に係わる脆化を回避する方策の開拓ができ，社会的意義も高いといえる．