435 ラメラ構造を有するTiAl基合金のマイクロスケール破壊試験(T09-3 微小機械システムにおけるマイクロ・ナノ力学(3) マイクロ・ナノ実験力学,大会テーマセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

概要

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Fracture tests of micro-sized TiAl PST specimens have been carried out, and the size effect on fracture toughness has been investigated. Micro-sized cantilever specimens with a size ≈ 10×20×50 μm^3 were prepared from Ti-48Al PST crystals by focused ion beam machining. Notches with a width of 0.5 μm and a depth of 5〜10 μm were also introduced into the micro-sized specimens by focused ion beam machining. Fracture tests were carried out using a mechanical testing machine for micro-sized specimens. The fracture toughness values obtained were dependent on the lamellar orientations ahead of the notch, and were in the range 1.5-8.1 MPam^<1/2>. These fracture toughness values are lower than those having been previously reported in conventional TiAl PST samples. For macro-sized specimens, extrinsic toughening mechanisms, including shear ligament bridging, act in the crack wake, and crack growth resistance increases rapidly with increasing length of crack wake for lamellar structured TiAl alloys. In contrast, the crack length in microsized specimens is only 2-3 μm. This indicates that extrinsic toughening mechanisms are not activated in micro-sized specimens. The results obtained in this investigation give important and fundamental information when applying TiAl to MEMS devices.
一般社団法人日本機械学会の論文
2008-08-02