Understanding of diversity in thermoelastic martensitic transformation by hierarchical microscopy studies

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H00829
• 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: Kyushu University
• Principal Investigator: Nishida Minoru 九州大学, 総合理工学研究院, 特任教授 (90183540)
• Co-Investigator(Kenkyū-buntansha): 赤嶺 大志 九州大学, 総合理工学研究院, 助教 (40804737) ; 松田 光弘 熊本大学, 大学院先端科学研究部(工), 准教授 (80332865)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 熱弾性マルテンサイト変態 / 形状記憶・超弾性合金 / 階層的顕微解析 / 自己調整構造 / 変態誘起転位 / 非金属介在物 / 走査電子顕微鏡用試料冷却ステージ / Strain Glass

Outline of Final Research Achievements

Stress-induced martensitic phase of Ti-Ni alloys was observed to have different internal defects from thermally induced M phase depending on the formation conditions. Two-step stress-induced transformation of Cu-Al-Mn alloy single crystals was found, and temperature-stress phase diagram was established. The results of hierarchical microscopic observation experimentally showed that transformation induced dislocations in Ti-Ni alloys are generated not during the forward transformation, as has been conventionally assumed, but during the reverse transformation. This result provided guidelines for the development of alloy systems that do not appear functional degradation. Strain glass-like behavior was found in Ti-Pd-Hf alloys.

Free Research Field

材料組織学

Academic Significance and Societal Importance of the Research Achievements

明らかになった応力誘起M相と熱誘起M相の相違をさらに解析することで，M変態の結晶学の深化が図られる．Cu-Al-Mn合金単結晶の応力‐温度状態図は耐震部材等への応用において，設計基準の設定等に重要な情報を与える．変態誘起転位と自己調整構造の関係および前者の生成機構の解明によって，機能劣化の生じないTi-Ni系合金の開発指針が得られた．医療用Ti-Ni超弾性合金の経年劣化が等温R相変態に起因し，その抑制が保管時の温度管理によって可能であることを明らかにした．Ti-Pd-Hf合金におけるStrain Glass的な現象の要因が，これまで提唱されてきたものとは異なる可能性が示唆された．