Mechanism of high plastic deformability of Ti-O L-PBF alloy

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K20488
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0401:Materials engineering, chemical engineering, and related fields
• Research Institution: Osaka University
• Principal Investigator: Kariya Shota 大阪大学, 接合科学研究所, 助教 (10912727)
• Project Period (FY): 2021-08-30 – 2023-03-31
• Keywords: チタン / 酸素 / 固溶強化 / 積層造形 / 塑性変形機構 / その場観察

Outline of Final Research Achievements

We have achieved an elucidation of the mechanism that enables both excellent strength and ductility in titanium L-PBF alloys with high oxygen in solid solution. Conventional Ti-O alloys are composed of α-Ti equiaxed grains, whereas the L-PBF Ti-O alloys are composed of /α'-Ti acicular grains. In-situ SEM-EBSD analysis of the tensile deformation process revealed the formation of deformation twins, which are considered inactive in Ti-O alloys, and lattice rotation that is different from the slip system reported in the conventional Ti-O alloys. These results indicate that the activation of plastic deformation system (basal slip and twin deformation), which are conventionally inactive, is accompanied by the formation of α'-Ti, resulting in the high ductility.

Free Research Field

金属積層造形

Academic Significance and Societal Importance of the Research Achievements

本研究成果は従来脆性とされてきたTi-O合金の信頼性向上のために不可欠であり，その塑性変形能を検討するにあたって，積層造形合金では，その結晶組織や酸素の分布のみならず，結晶構造の評価が必要であることを明らかにした．また，積層造形Ti-O合金にて確認された塑性変形機構は，Ti-O系のみならず，積層造形チタン合金として最も使用量の多いTi-64合金を含むnear αチタン合金にも共通であると予測される．したがって，本知見は積層造形チタン合金の理解にも有用であると考えられ，これを発展させて結晶構造と塑性変形機構の観点に基づいた積層造形Ti-64合金の熱処理の最適化とその原理解明を計画している．