Prediction of deformation localization and fracture in polycrystalline titanium alloy based on 3D measurement of ultra-small inhomogeneous deformation

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H01214
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 18010:Mechanics of materials and materials-related
• Research Institution: Okayama University
• Principal Investigator: Tada Naoya 岡山大学, 環境生命自然科学学域, 教授 (70243053)
• Co-Investigator(Kenkyū-buntansha): 上森 武 岡山大学, 環境生命自然科学学域, 准教授 (70335701) ; 坂本 惇司 岡山大学, 環境生命自然科学学域, 助教 (50752052)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: チタン合金 / 不均一変形 / 変形の局所化 / 破壊

Outline of Final Research Achievements

Tensile tests were carried out using flat plate, thin film, and thin wire specimens of polycrystalline pure titanium, and flat plate specimens of Ti-6Al-4V alloy. Microscopic inhomogeneous deformation caused by elastic tension, subsequent plastic inhomogeneous deformation, and final fracture were investigated. Furthermore, finite element analysis was conducted for tension of polycrystalline pure titanium using polycrystalline models. As a result, the initiation of slip lines could be predicted based on the slip activity, regardless of the shape of the specimen or the presence or absence of macroscopic stress concentration. But the final fracture morphology of thin wire was found to depend on the grain size. However, the Ti-6Al-4V alloy exhibits a peculiar deformation behavior under tension, in which deformation progressed with coalescence of microcracks. Further investigation is required.

Free Research Field

固体力学

Academic Significance and Societal Importance of the Research Achievements

本研究では，多結晶純チタンおよびTi-6Al-4Vチタン合金の薄膜，細線，平板の試験片を用いて引張試験を実施し，微視的不均一変形を，初期の弾性状態から後続の塑性状態，さらには破壊に至るまで詳細に観察・測定した．Ti-6Al-4Vチタン合金に関しては，課題が残っているが，多結晶純チタンに関しては，試験前に測定する結晶粒の幾何学的情報と巨視的応力分布がわかれば，すべり発生の予測が可能であることがわかった．本予測手法は，医療等で用いられている純チタン部材の設計や破壊防止に有用であると考える．