Study on the Deformation and Fracture Mechanism of Titanium by Means of Acoustic Emission Analysis : Part 2.Roles of the Surface Layered Structure of Titanium Cast into a Phosphate-bonded Silica Alumina Investment Mold

DOI 3 Citations
  • MIYAKAWA Osamu
    Dental Materials and Technology, Niigata University School of Dentistry
  • WATANABE Kouichi
    Dental Materials and Technology, Niigata University School of Dentistry
  • OKAWA Seigo
    Dental Materials and Technology, Niigata University School of Dentistry
  • NAKANO Syuji
    Dental Materials and Technology, Niigata University School of Dentistry
  • HONMA Hiro
    Dental Materials and Technology, Niigata University School of Dentistry
  • SHIOKAWA Nobuhiro
    Dental Materials and Technology, Niigata University School of Dentistry
  • KOBAYASHI Masayoshi
    EMX Laboratory, Niigata University
  • TAMURA Hisashi
    Department of Machinery System Engineering, Faculty of Engineering, Niigata University

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Other Title
  • アコースティックエミッション解析によるチタンの変形・破壊機構に関する研究 : 第2報 シリカ-アルミナ-リン酸塩埋没材の鋳型に鋳造したチタン表層の多層構造組織の役割

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The deformation and fracture mechanism of titanium cast into a phosphate-bonded silica alumina investment mold was examined by means of 3-point bending test, acoustic emission(AE)analysis, and metallographic examination.The α case formed on the casting increased the elastic limit and the maximum load, and so the removal of the surface by pickling decreased them.For the as-cast, sharp cracks propagated through the Si, P-rich layer into the acicular structure in the elastic deformation stage and then opened in the plastic deformation stage.As with the room-temperature mold casting, low-amplitude AEs were generated at a constant rate throughout the entire deformation process, in which crack formation, propagation, and opening occurred in the tension-side surface ranging from the center to both the end supports.As with the 800℃ mold casting, low-amplitude but high-energy AEs of a continuous type were generated during the elastic deformation, and they suggested simultaneous propagation of the primary crack.In the latter half stage of plastic deformation, the load and the AE rate were remarkably reduced.This is because a few main cracks near the center propagated continuously within the internal structure which possesses little resistance to the crack propagation.As with the pickled casting, AEs were generated not in the elastic deformation stage but in the plastic deformation stage, thus releasing high energy.The cause of such high-amplitude AEs is obscure.

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