クリスタル対称性とマルテンシート変換の可逆性
Kaushik Bhattacharya1, Sergio Conti, Giovanni Zanzotto
1Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125, USA. bhatta@caltech.edu
Nature
|March 6, 2004
まとめ
マルテンシート変換は,結晶対称性に基づいて,可逆的または不可逆的な行動を示す. 形状記憶合金における可逆性は,共有の対称性グループと関連しており,最小限の可塑性での変換を可能にします.
科学分野:
- マテリアルサイエンス 材料科学
- 固体物理 固体物理学
- クリスタルグラフィーです.
背景:
- マルテンシート変換は,様々な材料で観察される無拡散の相変化である.
- これらの移行は,結晶構造の急速な変化と微細構造の発達を伴う.
- 変換は不可逆的 (例えば,冷却鋼) または可逆的 (例えば,形状記憶合金) であり得る.
研究 の 目的:
- マルテンシート変換の逆転性の違いの根本的な理由を解明する.
- リバーシブル対不可逆的なマルテンシート行動を説明する理論的枠組みを確立する.
- 顕微鏡の可逆性を,基礎となる結晶の対称性の変化と結びつけるために.
主な方法:
- 数学理論と数値シミュレーションが採用されました.
- 分析は,マルテンシート変換中の結晶対称性の変化に焦点を当てた.
- 格子不変切断と相変化のためのエネルギー障壁が調査されました.
主要な成果:
- 逆転性の必要条件は,親相対称群と産物相対称群を共通の有限対称群に含めることです.
- この条件が満たされると,格子不変切断に対するエネルギー障壁は相変化のエネルギー障壁を上回り,ほぼ可塑性のない変換を可能にします.
- 他のケースでは,プラスチックの変形に対するエネルギー障壁が相変化障壁より高くないため,不可逆性が避けられない.
結論:
- 結晶対称性は,マルテンシート変換のマクロスコープの可逆性を決定する.
- この発見は,形状記憶合金およびその他のマルテンシート現象の振る舞いを理解するための理論的基礎を提供します.
- 実験的観測は,変換の可逆性を決定する上で対称性の重要な役割を裏付けている.
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